| # SPDX-License-Identifier: GPL-2.0+ |
| # |
| # (C) Copyright 2000 - 2013 |
| # Wolfgang Denk, DENX Software Engineering, wd@denx.de. |
| |
| Summary: |
| ======== |
| |
| This directory contains the source code for U-Boot, a boot loader for |
| Embedded boards based on PowerPC, ARM, MIPS and several other |
| processors, which can be installed in a boot ROM and used to |
| initialize and test the hardware or to download and run application |
| code. |
| |
| The development of U-Boot is closely related to Linux: some parts of |
| the source code originate in the Linux source tree, we have some |
| header files in common, and special provision has been made to |
| support booting of Linux images. |
| |
| Some attention has been paid to make this software easily |
| configurable and extendable. For instance, all monitor commands are |
| implemented with the same call interface, so that it's very easy to |
| add new commands. Also, instead of permanently adding rarely used |
| code (for instance hardware test utilities) to the monitor, you can |
| load and run it dynamically. |
| |
| |
| Status: |
| ======= |
| |
| In general, all boards for which a default configuration file exists in the |
| configs/ directory have been tested to some extent and can be considered |
| "working". In fact, many of them are used in production systems. |
| |
| In case of problems you can use |
| |
| scripts/get_maintainer.pl <path> |
| |
| to identify the people or companies responsible for various boards and |
| subsystems. Or have a look at the git log. |
| |
| |
| Where to get help: |
| ================== |
| |
| In case you have questions about, problems with or contributions for |
| U-Boot, you should send a message to the U-Boot mailing list at |
| <u-boot@lists.denx.de>. There is also an archive of previous traffic |
| on the mailing list - please search the archive before asking FAQ's. |
| Please see https://lists.denx.de/pipermail/u-boot and |
| https://marc.info/?l=u-boot |
| |
| Where to get source code: |
| ========================= |
| |
| The U-Boot source code is maintained in the Git repository at |
| https://source.denx.de/u-boot/u-boot.git ; you can browse it online at |
| https://source.denx.de/u-boot/u-boot |
| |
| The "Tags" links on this page allow you to download tarballs of |
| any version you might be interested in. Official releases are also |
| available from the DENX file server through HTTPS or FTP. |
| https://ftp.denx.de/pub/u-boot/ |
| ftp://ftp.denx.de/pub/u-boot/ |
| |
| |
| Where we come from: |
| =================== |
| |
| - start from 8xxrom sources |
| - create PPCBoot project (https://sourceforge.net/projects/ppcboot) |
| - clean up code |
| - make it easier to add custom boards |
| - make it possible to add other [PowerPC] CPUs |
| - extend functions, especially: |
| * Provide extended interface to Linux boot loader |
| * S-Record download |
| * network boot |
| * ATA disk / SCSI ... boot |
| - create ARMBoot project (https://sourceforge.net/projects/armboot) |
| - add other CPU families (starting with ARM) |
| - create U-Boot project (https://sourceforge.net/projects/u-boot) |
| - current project page: see https://www.denx.de/wiki/U-Boot |
| |
| |
| Names and Spelling: |
| =================== |
| |
| The "official" name of this project is "Das U-Boot". The spelling |
| "U-Boot" shall be used in all written text (documentation, comments |
| in source files etc.). Example: |
| |
| This is the README file for the U-Boot project. |
| |
| File names etc. shall be based on the string "u-boot". Examples: |
| |
| include/asm-ppc/u-boot.h |
| |
| #include <asm/u-boot.h> |
| |
| Variable names, preprocessor constants etc. shall be either based on |
| the string "u_boot" or on "U_BOOT". Example: |
| |
| U_BOOT_VERSION u_boot_logo |
| IH_OS_U_BOOT u_boot_hush_start |
| |
| |
| Software Configuration: |
| ======================= |
| |
| Selection of Processor Architecture and Board Type: |
| --------------------------------------------------- |
| |
| For all supported boards there are ready-to-use default |
| configurations available; just type "make <board_name>_defconfig". |
| |
| Example: For a TQM823L module type: |
| |
| cd u-boot |
| make TQM823L_defconfig |
| |
| Note: If you're looking for the default configuration file for a board |
| you're sure used to be there but is now missing, check the file |
| doc/README.scrapyard for a list of no longer supported boards. |
| |
| Sandbox Environment: |
| -------------------- |
| |
| U-Boot can be built natively to run on a Linux host using the 'sandbox' |
| board. This allows feature development which is not board- or architecture- |
| specific to be undertaken on a native platform. The sandbox is also used to |
| run some of U-Boot's tests. |
| |
| See doc/arch/sandbox/sandbox.rst for more details. |
| |
| |
| Board Initialisation Flow: |
| -------------------------- |
| |
| This is the intended start-up flow for boards. This should apply for both |
| SPL and U-Boot proper (i.e. they both follow the same rules). |
| |
| Note: "SPL" stands for "Secondary Program Loader," which is explained in |
| more detail later in this file. |
| |
| At present, SPL mostly uses a separate code path, but the function names |
| and roles of each function are the same. Some boards or architectures |
| may not conform to this. At least most ARM boards which use |
| CONFIG_SPL_FRAMEWORK conform to this. |
| |
| Execution typically starts with an architecture-specific (and possibly |
| CPU-specific) start.S file, such as: |
| |
| - arch/arm/cpu/armv7/start.S |
| - arch/powerpc/cpu/mpc83xx/start.S |
| - arch/mips/cpu/start.S |
| |
| and so on. From there, three functions are called; the purpose and |
| limitations of each of these functions are described below. |
| |
| lowlevel_init(): |
| - purpose: essential init to permit execution to reach board_init_f() |
| - no global_data or BSS |
| - there is no stack (ARMv7 may have one but it will soon be removed) |
| - must not set up SDRAM or use console |
| - must only do the bare minimum to allow execution to continue to |
| board_init_f() |
| - this is almost never needed |
| - return normally from this function |
| |
| board_init_f(): |
| - purpose: set up the machine ready for running board_init_r(): |
| i.e. SDRAM and serial UART |
| - global_data is available |
| - stack is in SRAM |
| - BSS is not available, so you cannot use global/static variables, |
| only stack variables and global_data |
| |
| Non-SPL-specific notes: |
| - dram_init() is called to set up DRAM. If already done in SPL this |
| can do nothing |
| |
| SPL-specific notes: |
| - you can override the entire board_init_f() function with your own |
| version as needed. |
| - preloader_console_init() can be called here in extremis |
| - should set up SDRAM, and anything needed to make the UART work |
| - there is no need to clear BSS, it will be done by crt0.S |
| - for specific scenarios on certain architectures an early BSS *can* |
| be made available (via CONFIG_SPL_EARLY_BSS by moving the clearing |
| of BSS prior to entering board_init_f()) but doing so is discouraged. |
| Instead it is strongly recommended to architect any code changes |
| or additions such to not depend on the availability of BSS during |
| board_init_f() as indicated in other sections of this README to |
| maintain compatibility and consistency across the entire code base. |
| - must return normally from this function (don't call board_init_r() |
| directly) |
| |
| Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at |
| this point the stack and global_data are relocated to below |
| CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of |
| memory. |
| |
| board_init_r(): |
| - purpose: main execution, common code |
| - global_data is available |
| - SDRAM is available |
| - BSS is available, all static/global variables can be used |
| - execution eventually continues to main_loop() |
| |
| Non-SPL-specific notes: |
| - U-Boot is relocated to the top of memory and is now running from |
| there. |
| |
| SPL-specific notes: |
| - stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and |
| CONFIG_SYS_FSL_HAS_CCI400 |
| |
| Defined For SoC that has cache coherent interconnect |
| CCN-400 |
| |
| CONFIG_SYS_FSL_HAS_CCN504 |
| |
| Defined for SoC that has cache coherent interconnect CCN-504 |
| |
| The following options need to be configured: |
| |
| - CPU Type: Define exactly one, e.g. CONFIG_MPC85XX. |
| |
| - Board Type: Define exactly one, e.g. CONFIG_MPC8540ADS. |
| |
| - 85xx CPU Options: |
| CONFIG_SYS_PPC64 |
| |
| Specifies that the core is a 64-bit PowerPC implementation (implements |
| the "64" category of the Power ISA). This is necessary for ePAPR |
| compliance, among other possible reasons. |
| |
| CONFIG_SYS_FSL_ERRATUM_A004510 |
| |
| Enables a workaround for erratum A004510. If set, |
| then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and |
| CFG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set. |
| |
| CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV |
| CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional) |
| |
| Defines one or two SoC revisions (low 8 bits of SVR) |
| for which the A004510 workaround should be applied. |
| |
| The rest of SVR is either not relevant to the decision |
| of whether the erratum is present (e.g. p2040 versus |
| p2041) or is implied by the build target, which controls |
| whether CONFIG_SYS_FSL_ERRATUM_A004510 is set. |
| |
| See Freescale App Note 4493 for more information about |
| this erratum. |
| |
| CFG_SYS_FSL_CORENET_SNOOPVEC_COREONLY |
| |
| This is the value to write into CCSR offset 0x18600 |
| according to the A004510 workaround. |
| |
| CONFIG_SYS_FSL_SINGLE_SOURCE_CLK |
| Single Source Clock is clocking mode present in some of FSL SoC's. |
| In this mode, a single differential clock is used to supply |
| clocks to the sysclock, ddrclock and usbclock. |
| |
| - Generic CPU options: |
| |
| CONFIG_SYS_FSL_DDR |
| Freescale DDR driver in use. This type of DDR controller is |
| found in mpc83xx, mpc85xx as well as some ARM core SoCs. |
| |
| CFG_SYS_FSL_DDR_ADDR |
| Freescale DDR memory-mapped register base. |
| |
| CONFIG_SYS_FSL_IFC_CLK_DIV |
| Defines divider of platform clock(clock input to IFC controller). |
| |
| CONFIG_SYS_FSL_LBC_CLK_DIV |
| Defines divider of platform clock(clock input to eLBC controller). |
| |
| CFG_SYS_FSL_DDR_SDRAM_BASE_PHY |
| Physical address from the view of DDR controllers. It is the |
| same as CFG_SYS_DDR_SDRAM_BASE for all Power SoCs. But |
| it could be different for ARM SoCs. |
| |
| - ARM options: |
| CFG_SYS_EXCEPTION_VECTORS_HIGH |
| |
| Select high exception vectors of the ARM core, e.g., do not |
| clear the V bit of the c1 register of CP15. |
| |
| COUNTER_FREQUENCY |
| Generic timer clock source frequency. |
| |
| COUNTER_FREQUENCY_REAL |
| Generic timer clock source frequency if the real clock is |
| different from COUNTER_FREQUENCY, and can only be determined |
| at run time. |
| |
| - Linux Kernel Interface: |
| CONFIG_OF_LIBFDT |
| |
| New kernel versions are expecting firmware settings to be |
| passed using flattened device trees (based on open firmware |
| concepts). |
| |
| CONFIG_OF_LIBFDT |
| * New libfdt-based support |
| * Adds the "fdt" command |
| * The bootm command automatically updates the fdt |
| |
| OF_TBCLK - The timebase frequency. |
| |
| boards with QUICC Engines require OF_QE to set UCC MAC |
| addresses |
| |
| CONFIG_OF_IDE_FIXUP |
| |
| U-Boot can detect if an IDE device is present or not. |
| If not, and this new config option is activated, U-Boot |
| removes the ATA node from the DTS before booting Linux, |
| so the Linux IDE driver does not probe the device and |
| crash. This is needed for buggy hardware (uc101) where |
| no pull down resistor is connected to the signal IDE5V_DD7. |
| |
| - vxWorks boot parameters: |
| |
| bootvx constructs a valid bootline using the following |
| environments variables: bootdev, bootfile, ipaddr, netmask, |
| serverip, gatewayip, hostname, othbootargs. |
| It loads the vxWorks image pointed bootfile. |
| |
| Note: If a "bootargs" environment is defined, it will override |
| the defaults discussed just above. |
| |
| - Cache Configuration for ARM: |
| CFG_SYS_PL310_BASE - Physical base address of PL310 |
| controller register space |
| |
| - Serial Ports: |
| CFG_PL011_CLOCK |
| |
| If you have Amba PrimeCell PL011 UARTs, set this variable to |
| the clock speed of the UARTs. |
| |
| CFG_PL01x_PORTS |
| |
| If you have Amba PrimeCell PL010 or PL011 UARTs on your board, |
| define this to a list of base addresses for each (supported) |
| port. See e.g. include/configs/versatile.h |
| |
| CONFIG_SERIAL_HW_FLOW_CONTROL |
| |
| Define this variable to enable hw flow control in serial driver. |
| Current user of this option is drivers/serial/nsl16550.c driver |
| |
| - Removal of commands |
| If no commands are needed to boot, you can disable |
| CONFIG_CMDLINE to remove them. In this case, the command line |
| will not be available, and when U-Boot wants to execute the |
| boot command (on start-up) it will call board_run_command() |
| instead. This can reduce image size significantly for very |
| simple boot procedures. |
| |
| - Regular expression support: |
| CONFIG_REGEX |
| If this variable is defined, U-Boot is linked against |
| the SLRE (Super Light Regular Expression) library, |
| which adds regex support to some commands, as for |
| example "env grep" and "setexpr". |
| |
| - Watchdog: |
| CFG_SYS_WATCHDOG_FREQ |
| Some platforms automatically call WATCHDOG_RESET() |
| from the timer interrupt handler every |
| CFG_SYS_WATCHDOG_FREQ interrupts. If not set by the |
| board configuration file, a default of CONFIG_SYS_HZ/2 |
| (i.e. 500) is used. Setting CFG_SYS_WATCHDOG_FREQ |
| to 0 disables calling WATCHDOG_RESET() from the timer |
| interrupt. |
| |
| - GPIO Support: |
| The CFG_SYS_I2C_PCA953X_WIDTH option specifies a list of |
| chip-ngpio pairs that tell the PCA953X driver the number of |
| pins supported by a particular chip. |
| |
| Note that if the GPIO device uses I2C, then the I2C interface |
| must also be configured. See I2C Support, below. |
| |
| - I/O tracing: |
| When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O |
| accesses and can checksum them or write a list of them out |
| to memory. See the 'iotrace' command for details. This is |
| useful for testing device drivers since it can confirm that |
| the driver behaves the same way before and after a code |
| change. Currently this is supported on sandbox and arm. To |
| add support for your architecture, add '#include <iotrace.h>' |
| to the bottom of arch/<arch>/include/asm/io.h and test. |
| |
| Example output from the 'iotrace stats' command is below. |
| Note that if the trace buffer is exhausted, the checksum will |
| still continue to operate. |
| |
| iotrace is enabled |
| Start: 10000000 (buffer start address) |
| Size: 00010000 (buffer size) |
| Offset: 00000120 (current buffer offset) |
| Output: 10000120 (start + offset) |
| Count: 00000018 (number of trace records) |
| CRC32: 9526fb66 (CRC32 of all trace records) |
| |
| - Timestamp Support: |
| |
| When CONFIG_TIMESTAMP is selected, the timestamp |
| (date and time) of an image is printed by image |
| commands like bootm or iminfo. This option is |
| automatically enabled when you select CONFIG_CMD_DATE . |
| |
| - Partition Labels (disklabels) Supported: |
| Zero or more of the following: |
| CONFIG_MAC_PARTITION Apple's MacOS partition table. |
| CONFIG_ISO_PARTITION ISO partition table, used on CDROM etc. |
| CONFIG_EFI_PARTITION GPT partition table, common when EFI is the |
| bootloader. Note 2TB partition limit; see |
| disk/part_efi.c |
| CONFIG_SCSI) you must configure support for at |
| least one non-MTD partition type as well. |
| |
| - NETWORK Support (PCI): |
| CONFIG_E1000_SPI |
| Utility code for direct access to the SPI bus on Intel 8257x. |
| This does not do anything useful unless you set at least one |
| of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC. |
| |
| CONFIG_NATSEMI |
| Support for National dp83815 chips. |
| |
| CONFIG_NS8382X |
| Support for National dp8382[01] gigabit chips. |
| |
| - NETWORK Support (other): |
| CONFIG_CALXEDA_XGMAC |
| Support for the Calxeda XGMAC device |
| |
| CONFIG_LAN91C96 |
| Support for SMSC's LAN91C96 chips. |
| |
| CONFIG_LAN91C96_USE_32_BIT |
| Define this to enable 32 bit addressing |
| |
| CFG_SYS_DAVINCI_EMAC_PHY_COUNT |
| Define this if you have more then 3 PHYs. |
| |
| CONFIG_FTGMAC100 |
| Support for Faraday's FTGMAC100 Gigabit SoC Ethernet |
| |
| CONFIG_FTGMAC100_EGIGA |
| Define this to use GE link update with gigabit PHY. |
| Define this if FTGMAC100 is connected to gigabit PHY. |
| If your system has 10/100 PHY only, it might not occur |
| wrong behavior. Because PHY usually return timeout or |
| useless data when polling gigabit status and gigabit |
| control registers. This behavior won't affect the |
| correctnessof 10/100 link speed update. |
| |
| CONFIG_SH_ETHER |
| Support for Renesas on-chip Ethernet controller |
| |
| CFG_SH_ETHER_USE_PORT |
| Define the number of ports to be used |
| |
| CFG_SH_ETHER_PHY_ADDR |
| Define the ETH PHY's address |
| |
| CFG_SH_ETHER_CACHE_WRITEBACK |
| If this option is set, the driver enables cache flush. |
| |
| - TPM Support: |
| CONFIG_TPM |
| Support TPM devices. |
| |
| CONFIG_TPM_TIS_INFINEON |
| Support for Infineon i2c bus TPM devices. Only one device |
| per system is supported at this time. |
| |
| CONFIG_TPM_TIS_I2C_BURST_LIMITATION |
| Define the burst count bytes upper limit |
| |
| CONFIG_TPM_ST33ZP24 |
| Support for STMicroelectronics TPM devices. Requires DM_TPM support. |
| |
| CONFIG_TPM_ST33ZP24_I2C |
| Support for STMicroelectronics ST33ZP24 I2C devices. |
| Requires TPM_ST33ZP24 and I2C. |
| |
| CONFIG_TPM_ST33ZP24_SPI |
| Support for STMicroelectronics ST33ZP24 SPI devices. |
| Requires TPM_ST33ZP24 and SPI. |
| |
| CONFIG_TPM_ATMEL_TWI |
| Support for Atmel TWI TPM device. Requires I2C support. |
| |
| CONFIG_TPM_TIS_LPC |
| Support for generic parallel port TPM devices. Only one device |
| per system is supported at this time. |
| |
| CONFIG_TPM |
| Define this to enable the TPM support library which provides |
| functional interfaces to some TPM commands. |
| Requires support for a TPM device. |
| |
| CONFIG_TPM_AUTH_SESSIONS |
| Define this to enable authorized functions in the TPM library. |
| Requires CONFIG_TPM and CONFIG_SHA1. |
| |
| - USB Support: |
| At the moment only the UHCI host controller is |
| supported (PIP405, MIP405); define |
| CONFIG_USB_UHCI to enable it. |
| define CONFIG_USB_KEYBOARD to enable the USB Keyboard |
| and define CONFIG_USB_STORAGE to enable the USB |
| storage devices. |
| Note: |
| Supported are USB Keyboards and USB Floppy drives |
| (TEAC FD-05PUB). |
| |
| CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2 |
| HW module registers. |
| |
| - USB Device: |
| Define the below if you wish to use the USB console. |
| Once firmware is rebuilt from a serial console issue the |
| command "setenv stdin usbtty; setenv stdout usbtty" and |
| attach your USB cable. The Unix command "dmesg" should print |
| it has found a new device. The environment variable usbtty |
| can be set to gserial or cdc_acm to enable your device to |
| appear to a USB host as a Linux gserial device or a |
| Common Device Class Abstract Control Model serial device. |
| If you select usbtty = gserial you should be able to enumerate |
| a Linux host by |
| # modprobe usbserial vendor=0xVendorID product=0xProductID |
| else if using cdc_acm, simply setting the environment |
| variable usbtty to be cdc_acm should suffice. The following |
| might be defined in YourBoardName.h |
| |
| If you have a USB-IF assigned VendorID then you may wish to |
| define your own vendor specific values either in BoardName.h |
| or directly in usbd_vendor_info.h. If you don't define |
| CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME, |
| CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot |
| should pretend to be a Linux device to it's target host. |
| |
| CONFIG_USBD_MANUFACTURER |
| Define this string as the name of your company for |
| - CONFIG_USBD_MANUFACTURER "my company" |
| |
| CONFIG_USBD_PRODUCT_NAME |
| Define this string as the name of your product |
| - CONFIG_USBD_PRODUCT_NAME "acme usb device" |
| |
| CONFIG_USBD_VENDORID |
| Define this as your assigned Vendor ID from the USB |
| Implementors Forum. This *must* be a genuine Vendor ID |
| to avoid polluting the USB namespace. |
| - CONFIG_USBD_VENDORID 0xFFFF |
| |
| CONFIG_USBD_PRODUCTID |
| Define this as the unique Product ID |
| for your device |
| - CONFIG_USBD_PRODUCTID 0xFFFF |
| |
| - ULPI Layer Support: |
| The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via |
| the generic ULPI layer. The generic layer accesses the ULPI PHY |
| via the platform viewport, so you need both the genric layer and |
| the viewport enabled. Currently only Chipidea/ARC based |
| viewport is supported. |
| To enable the ULPI layer support, define CONFIG_USB_ULPI and |
| CONFIG_USB_ULPI_VIEWPORT in your board configuration file. |
| If your ULPI phy needs a different reference clock than the |
| standard 24 MHz then you have to define CFG_ULPI_REF_CLK to |
| the appropriate value in Hz. |
| |
| - MMC Support: |
| CONFIG_SH_MMCIF |
| Support for Renesas on-chip MMCIF controller |
| |
| CONFIG_SH_MMCIF_ADDR |
| Define the base address of MMCIF registers |
| |
| CONFIG_SH_MMCIF_CLK |
| Define the clock frequency for MMCIF |
| |
| - USB Device Firmware Update (DFU) class support: |
| CONFIG_DFU_OVER_USB |
| This enables the USB portion of the DFU USB class |
| |
| CONFIG_DFU_NAND |
| This enables support for exposing NAND devices via DFU. |
| |
| CONFIG_DFU_RAM |
| This enables support for exposing RAM via DFU. |
| Note: DFU spec refer to non-volatile memory usage, but |
| allow usages beyond the scope of spec - here RAM usage, |
| one that would help mostly the developer. |
| |
| CONFIG_SYS_DFU_DATA_BUF_SIZE |
| Dfu transfer uses a buffer before writing data to the |
| raw storage device. Make the size (in bytes) of this buffer |
| configurable. The size of this buffer is also configurable |
| through the "dfu_bufsiz" environment variable. |
| |
| CONFIG_SYS_DFU_MAX_FILE_SIZE |
| When updating files rather than the raw storage device, |
| we use a static buffer to copy the file into and then write |
| the buffer once we've been given the whole file. Define |
| this to the maximum filesize (in bytes) for the buffer. |
| Default is 4 MiB if undefined. |
| |
| DFU_DEFAULT_POLL_TIMEOUT |
| Poll timeout [ms], is the timeout a device can send to the |
| host. The host must wait for this timeout before sending |
| a subsequent DFU_GET_STATUS request to the device. |
| |
| DFU_MANIFEST_POLL_TIMEOUT |
| Poll timeout [ms], which the device sends to the host when |
| entering dfuMANIFEST state. Host waits this timeout, before |
| sending again an USB request to the device. |
| |
| - Keyboard Support: |
| See Kconfig help for available keyboard drivers. |
| |
| - MII/PHY support: |
| CONFIG_PHY_CLOCK_FREQ (ppc4xx) |
| |
| The clock frequency of the MII bus |
| |
| CONFIG_PHY_CMD_DELAY (ppc4xx) |
| |
| Some PHY like Intel LXT971A need extra delay after |
| command issued before MII status register can be read |
| |
| - BOOTP Recovery Mode: |
| CONFIG_BOOTP_RANDOM_DELAY |
| |
| If you have many targets in a network that try to |
| boot using BOOTP, you may want to avoid that all |
| systems send out BOOTP requests at precisely the same |
| moment (which would happen for instance at recovery |
| from a power failure, when all systems will try to |
| boot, thus flooding the BOOTP server. Defining |
| CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be |
| inserted before sending out BOOTP requests. The |
| following delays are inserted then: |
| |
| 1st BOOTP request: delay 0 ... 1 sec |
| 2nd BOOTP request: delay 0 ... 2 sec |
| 3rd BOOTP request: delay 0 ... 4 sec |
| 4th and following |
| BOOTP requests: delay 0 ... 8 sec |
| |
| CFG_BOOTP_ID_CACHE_SIZE |
| |
| BOOTP packets are uniquely identified using a 32-bit ID. The |
| server will copy the ID from client requests to responses and |
| U-Boot will use this to determine if it is the destination of |
| an incoming response. Some servers will check that addresses |
| aren't in use before handing them out (usually using an ARP |
| ping) and therefore take up to a few hundred milliseconds to |
| respond. Network congestion may also influence the time it |
| takes for a response to make it back to the client. If that |
| time is too long, U-Boot will retransmit requests. In order |
| to allow earlier responses to still be accepted after these |
| retransmissions, U-Boot's BOOTP client keeps a small cache of |
| IDs. The CFG_BOOTP_ID_CACHE_SIZE controls the size of this |
| cache. The default is to keep IDs for up to four outstanding |
| requests. Increasing this will allow U-Boot to accept offers |
| from a BOOTP client in networks with unusually high latency. |
| |
| - DHCP Advanced Options: |
| |
| - Link-local IP address negotiation: |
| Negotiate with other link-local clients on the local network |
| for an address that doesn't require explicit configuration. |
| This is especially useful if a DHCP server cannot be guaranteed |
| to exist in all environments that the device must operate. |
| |
| See doc/README.link-local for more information. |
| |
| - MAC address from environment variables |
| |
| FDT_SEQ_MACADDR_FROM_ENV |
| |
| Fix-up device tree with MAC addresses fetched sequentially from |
| environment variables. This config work on assumption that |
| non-usable ethernet node of device-tree are either not present |
| or their status has been marked as "disabled". |
| |
| - CDP Options: |
| CONFIG_CDP_DEVICE_ID |
| |
| The device id used in CDP trigger frames. |
| |
| CONFIG_CDP_DEVICE_ID_PREFIX |
| |
| A two character string which is prefixed to the MAC address |
| of the device. |
| |
| CONFIG_CDP_PORT_ID |
| |
| A printf format string which contains the ascii name of |
| the port. Normally is set to "eth%d" which sets |
| eth0 for the first Ethernet, eth1 for the second etc. |
| |
| CONFIG_CDP_CAPABILITIES |
| |
| A 32bit integer which indicates the device capabilities; |
| 0x00000010 for a normal host which does not forwards. |
| |
| CONFIG_CDP_VERSION |
| |
| An ascii string containing the version of the software. |
| |
| CONFIG_CDP_PLATFORM |
| |
| An ascii string containing the name of the platform. |
| |
| CONFIG_CDP_TRIGGER |
| |
| A 32bit integer sent on the trigger. |
| |
| CONFIG_CDP_POWER_CONSUMPTION |
| |
| A 16bit integer containing the power consumption of the |
| device in .1 of milliwatts. |
| |
| CONFIG_CDP_APPLIANCE_VLAN_TYPE |
| |
| A byte containing the id of the VLAN. |
| |
| - Status LED: CONFIG_LED_STATUS |
| |
| Several configurations allow to display the current |
| status using a LED. For instance, the LED will blink |
| fast while running U-Boot code, stop blinking as |
| soon as a reply to a BOOTP request was received, and |
| start blinking slow once the Linux kernel is running |
| (supported by a status LED driver in the Linux |
| kernel). Defining CONFIG_LED_STATUS enables this |
| feature in U-Boot. |
| |
| Additional options: |
| |
| CONFIG_LED_STATUS_GPIO |
| The status LED can be connected to a GPIO pin. |
| In such cases, the gpio_led driver can be used as a |
| status LED backend implementation. Define CONFIG_LED_STATUS_GPIO |
| to include the gpio_led driver in the U-Boot binary. |
| |
| CFG_GPIO_LED_INVERTED_TABLE |
| Some GPIO connected LEDs may have inverted polarity in which |
| case the GPIO high value corresponds to LED off state and |
| GPIO low value corresponds to LED on state. |
| In such cases CFG_GPIO_LED_INVERTED_TABLE may be defined |
| with a list of GPIO LEDs that have inverted polarity. |
| |
| - I2C Support: |
| CFG_SYS_NUM_I2C_BUSES |
| Hold the number of i2c buses you want to use. |
| |
| CFG_SYS_I2C_DIRECT_BUS |
| define this, if you don't use i2c muxes on your hardware. |
| if CFG_SYS_I2C_MAX_HOPS is not defined or == 0 you can |
| omit this define. |
| |
| CFG_SYS_I2C_MAX_HOPS |
| define how many muxes are maximal consecutively connected |
| on one i2c bus. If you not use i2c muxes, omit this |
| define. |
| |
| CFG_SYS_I2C_BUSES |
| hold a list of buses you want to use, only used if |
| CFG_SYS_I2C_DIRECT_BUS is not defined, for example |
| a board with CFG_SYS_I2C_MAX_HOPS = 1 and |
| CFG_SYS_NUM_I2C_BUSES = 9: |
| |
| CFG_SYS_I2C_BUSES {{0, {I2C_NULL_HOP}}, \ |
| {0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \ |
| {0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \ |
| {0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \ |
| {0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \ |
| {0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \ |
| {1, {I2C_NULL_HOP}}, \ |
| {1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \ |
| {1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \ |
| } |
| |
| which defines |
| bus 0 on adapter 0 without a mux |
| bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1 |
| bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2 |
| bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3 |
| bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4 |
| bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5 |
| bus 6 on adapter 1 without a mux |
| bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1 |
| bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2 |
| |
| If you do not have i2c muxes on your board, omit this define. |
| |
| - Legacy I2C Support: |
| If you use the software i2c interface (CONFIG_SYS_I2C_SOFT) |
| then the following macros need to be defined (examples are |
| from include/configs/lwmon.h): |
| |
| I2C_INIT |
| |
| (Optional). Any commands necessary to enable the I2C |
| controller or configure ports. |
| |
| eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |= PB_SCL) |
| |
| I2C_ACTIVE |
| |
| The code necessary to make the I2C data line active |
| (driven). If the data line is open collector, this |
| define can be null. |
| |
| eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |= PB_SDA) |
| |
| I2C_TRISTATE |
| |
| The code necessary to make the I2C data line tri-stated |
| (inactive). If the data line is open collector, this |
| define can be null. |
| |
| eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA) |
| |
| I2C_READ |
| |
| Code that returns true if the I2C data line is high, |
| false if it is low. |
| |
| eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0) |
| |
| I2C_SDA(bit) |
| |
| If <bit> is true, sets the I2C data line high. If it |
| is false, it clears it (low). |
| |
| eg: #define I2C_SDA(bit) \ |
| if(bit) immr->im_cpm.cp_pbdat |= PB_SDA; \ |
| else immr->im_cpm.cp_pbdat &= ~PB_SDA |
| |
| I2C_SCL(bit) |
| |
| If <bit> is true, sets the I2C clock line high. If it |
| is false, it clears it (low). |
| |
| eg: #define I2C_SCL(bit) \ |
| if(bit) immr->im_cpm.cp_pbdat |= PB_SCL; \ |
| else immr->im_cpm.cp_pbdat &= ~PB_SCL |
| |
| I2C_DELAY |
| |
| This delay is invoked four times per clock cycle so this |
| controls the rate of data transfer. The data rate thus |
| is 1 / (I2C_DELAY * 4). Often defined to be something |
| like: |
| |
| #define I2C_DELAY udelay(2) |
| |
| CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA |
| |
| If your arch supports the generic GPIO framework (asm/gpio.h), |
| then you may alternatively define the two GPIOs that are to be |
| used as SCL / SDA. Any of the previous I2C_xxx macros will |
| have GPIO-based defaults assigned to them as appropriate. |
| |
| You should define these to the GPIO value as given directly to |
| the generic GPIO functions. |
| |
| CFG_I2C_MULTI_BUS |
| |
| This option allows the use of multiple I2C buses, each of which |
| must have a controller. At any point in time, only one bus is |
| active. To switch to a different bus, use the 'i2c dev' command. |
| Note that bus numbering is zero-based. |
| |
| CFG_SYS_I2C_NOPROBES |
| |
| This option specifies a list of I2C devices that will be skipped |
| when the 'i2c probe' command is issued. |
| |
| e.g. |
| #define CFG_SYS_I2C_NOPROBES {0x50,0x68} |
| |
| will skip addresses 0x50 and 0x68 on a board with one I2C bus |
| |
| CFG_SYS_RTC_BUS_NUM |
| |
| If defined, then this indicates the I2C bus number for the RTC. |
| If not defined, then U-Boot assumes that RTC is on I2C bus 0. |
| |
| CONFIG_SOFT_I2C_READ_REPEATED_START |
| |
| defining this will force the i2c_read() function in |
| the soft_i2c driver to perform an I2C repeated start |
| between writing the address pointer and reading the |
| data. If this define is omitted the default behaviour |
| of doing a stop-start sequence will be used. Most I2C |
| devices can use either method, but some require one or |
| the other. |
| |
| - SPI Support: CONFIG_SPI |
| |
| Enables SPI driver (so far only tested with |
| SPI EEPROM, also an instance works with Crystal A/D and |
| D/As on the SACSng board) |
| |
| CFG_SYS_SPI_MXC_WAIT |
| Timeout for waiting until spi transfer completed. |
| default: (CONFIG_SYS_HZ/100) /* 10 ms */ |
| |
| - FPGA Support: CONFIG_FPGA |
| |
| Enables FPGA subsystem. |
| |
| CONFIG_FPGA_<vendor> |
| |
| Enables support for specific chip vendors. |
| (ALTERA, XILINX) |
| |
| CONFIG_FPGA_<family> |
| |
| Enables support for FPGA family. |
| (SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX) |
| |
| CONFIG_SYS_FPGA_CHECK_BUSY |
| |
| Enable checks on FPGA configuration interface busy |
| status by the configuration function. This option |
| will require a board or device specific function to |
| be written. |
| |
| CFG_FPGA_DELAY |
| |
| If defined, a function that provides delays in the FPGA |
| configuration driver. |
| |
| CFG_SYS_FPGA_CHECK_ERROR |
| |
| Check for configuration errors during FPGA bitfile |
| loading. For example, abort during Virtex II |
| configuration if the INIT_B line goes low (which |
| indicated a CRC error). |
| |
| CFG_SYS_FPGA_WAIT_INIT |
| |
| Maximum time to wait for the INIT_B line to de-assert |
| after PROB_B has been de-asserted during a Virtex II |
| FPGA configuration sequence. The default time is 500 |
| ms. |
| |
| CFG_SYS_FPGA_WAIT_BUSY |
| |
| Maximum time to wait for BUSY to de-assert during |
| Virtex II FPGA configuration. The default is 5 ms. |
| |
| CFG_SYS_FPGA_WAIT_CONFIG |
| |
| Time to wait after FPGA configuration. The default is |
| 200 ms. |
| |
| - Vendor Parameter Protection: |
| |
| U-Boot considers the values of the environment |
| variables "serial#" (Board Serial Number) and |
| "ethaddr" (Ethernet Address) to be parameters that |
| are set once by the board vendor / manufacturer, and |
| protects these variables from casual modification by |
| the user. Once set, these variables are read-only, |
| and write or delete attempts are rejected. You can |
| change this behaviour: |
| |
| If CONFIG_ENV_OVERWRITE is #defined in your config |
| file, the write protection for vendor parameters is |
| completely disabled. Anybody can change or delete |
| these parameters. |
| |
| The same can be accomplished in a more flexible way |
| for any variable by configuring the type of access |
| to allow for those variables in the ".flags" variable |
| or define CFG_ENV_FLAGS_LIST_STATIC. |
| |
| - Protected RAM: |
| CFG_PRAM |
| |
| Define this variable to enable the reservation of |
| "protected RAM", i. e. RAM which is not overwritten |
| by U-Boot. Define CFG_PRAM to hold the number of |
| kB you want to reserve for pRAM. You can overwrite |
| this default value by defining an environment |
| variable "pram" to the number of kB you want to |
| reserve. Note that the board info structure will |
| still show the full amount of RAM. If pRAM is |
| reserved, a new environment variable "mem" will |
| automatically be defined to hold the amount of |
| remaining RAM in a form that can be passed as boot |
| argument to Linux, for instance like that: |
| |
| setenv bootargs ... mem=\${mem} |
| saveenv |
| |
| This way you can tell Linux not to use this memory, |
| either, which results in a memory region that will |
| not be affected by reboots. |
| |
| *WARNING* If your board configuration uses automatic |
| detection of the RAM size, you must make sure that |
| this memory test is non-destructive. So far, the |
| following board configurations are known to be |
| "pRAM-clean": |
| |
| IVMS8, IVML24, SPD8xx, |
| HERMES, IP860, RPXlite, LWMON, |
| FLAGADM |
| |
| - Error Recovery: |
| Note: |
| |
| In the current implementation, the local variables |
| space and global environment variables space are |
| separated. Local variables are those you define by |
| simply typing `name=value'. To access a local |
| variable later on, you have write `$name' or |
| `${name}'; to execute the contents of a variable |
| directly type `$name' at the command prompt. |
| |
| Global environment variables are those you use |
| setenv/printenv to work with. To run a command stored |
| in such a variable, you need to use the run command, |
| and you must not use the '$' sign to access them. |
| |
| To store commands and special characters in a |
| variable, please use double quotation marks |
| surrounding the whole text of the variable, instead |
| of the backslashes before semicolons and special |
| symbols. |
| |
| - Default Environment: |
| CFG_EXTRA_ENV_SETTINGS |
| |
| Define this to contain any number of null terminated |
| strings (variable = value pairs) that will be part of |
| the default environment compiled into the boot image. |
| |
| For example, place something like this in your |
| board's config file: |
| |
| #define CFG_EXTRA_ENV_SETTINGS \ |
| "myvar1=value1\0" \ |
| "myvar2=value2\0" |
| |
| Warning: This method is based on knowledge about the |
| internal format how the environment is stored by the |
| U-Boot code. This is NOT an official, exported |
| interface! Although it is unlikely that this format |
| will change soon, there is no guarantee either. |
| You better know what you are doing here. |
| |
| Note: overly (ab)use of the default environment is |
| discouraged. Make sure to check other ways to preset |
| the environment like the "source" command or the |
| boot command first. |
| |
| CONFIG_DELAY_ENVIRONMENT |
| |
| Normally the environment is loaded when the board is |
| initialised so that it is available to U-Boot. This inhibits |
| that so that the environment is not available until |
| explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL |
| this is instead controlled by the value of |
| /config/load-environment. |
| |
| - Automatic software updates via TFTP server |
| CONFIG_UPDATE_TFTP |
| CONFIG_UPDATE_TFTP_CNT_MAX |
| CONFIG_UPDATE_TFTP_MSEC_MAX |
| |
| These options enable and control the auto-update feature; |
| for a more detailed description refer to doc/README.update. |
| |
| - MTD Support (mtdparts command, UBI support) |
| CONFIG_MTD_UBI_WL_THRESHOLD |
| This parameter defines the maximum difference between the highest |
| erase counter value and the lowest erase counter value of eraseblocks |
| of UBI devices. When this threshold is exceeded, UBI starts performing |
| wear leveling by means of moving data from eraseblock with low erase |
| counter to eraseblocks with high erase counter. |
| |
| The default value should be OK for SLC NAND flashes, NOR flashes and |
| other flashes which have eraseblock life-cycle 100000 or more. |
| However, in case of MLC NAND flashes which typically have eraseblock |
| life-cycle less than 10000, the threshold should be lessened (e.g., |
| to 128 or 256, although it does not have to be power of 2). |
| |
| default: 4096 |
| |
| CONFIG_MTD_UBI_BEB_LIMIT |
| This option specifies the maximum bad physical eraseblocks UBI |
| expects on the MTD device (per 1024 eraseblocks). If the |
| underlying flash does not admit of bad eraseblocks (e.g. NOR |
| flash), this value is ignored. |
| |
| NAND datasheets often specify the minimum and maximum NVM |
| (Number of Valid Blocks) for the flashes' endurance lifetime. |
| The maximum expected bad eraseblocks per 1024 eraseblocks |
| then can be calculated as "1024 * (1 - MinNVB / MaxNVB)", |
| which gives 20 for most NANDs (MaxNVB is basically the total |
| count of eraseblocks on the chip). |
| |
| To put it differently, if this value is 20, UBI will try to |
| reserve about 1.9% of physical eraseblocks for bad blocks |
| handling. And that will be 1.9% of eraseblocks on the entire |
| NAND chip, not just the MTD partition UBI attaches. This means |
| that if you have, say, a NAND flash chip admits maximum 40 bad |
| eraseblocks, and it is split on two MTD partitions of the same |
| size, UBI will reserve 40 eraseblocks when attaching a |
| partition. |
| |
| default: 20 |
| |
| CONFIG_MTD_UBI_FASTMAP |
| Fastmap is a mechanism which allows attaching an UBI device |
| in nearly constant time. Instead of scanning the whole MTD device it |
| only has to locate a checkpoint (called fastmap) on the device. |
| The on-flash fastmap contains all information needed to attach |
| the device. Using fastmap makes only sense on large devices where |
| attaching by scanning takes long. UBI will not automatically install |
| a fastmap on old images, but you can set the UBI parameter |
| CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note |
| that fastmap-enabled images are still usable with UBI implementations |
| without fastmap support. On typical flash devices the whole fastmap |
| fits into one PEB. UBI will reserve PEBs to hold two fastmaps. |
| |
| CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT |
| Set this parameter to enable fastmap automatically on images |
| without a fastmap. |
| default: 0 |
| |
| CONFIG_MTD_UBI_FM_DEBUG |
| Enable UBI fastmap debug |
| default: 0 |
| |
| - SPL framework |
| CONFIG_SPL |
| Enable building of SPL globally. |
| |
| CONFIG_SPL_PANIC_ON_RAW_IMAGE |
| When defined, SPL will panic() if the image it has |
| loaded does not have a signature. |
| Defining this is useful when code which loads images |
| in SPL cannot guarantee that absolutely all read errors |
| will be caught. |
| An example is the LPC32XX MLC NAND driver, which will |
| consider that a completely unreadable NAND block is bad, |
| and thus should be skipped silently. |
| |
| CONFIG_SPL_DISPLAY_PRINT |
| For ARM, enable an optional function to print more information |
| about the running system. |
| |
| CONFIG_SPL_MPC83XX_WAIT_FOR_NAND |
| Set this for NAND SPL on PPC mpc83xx targets, so that |
| start.S waits for the rest of the SPL to load before |
| continuing (the hardware starts execution after just |
| loading the first page rather than the full 4K). |
| |
| CONFIG_SPL_UBI |
| Support for a lightweight UBI (fastmap) scanner and |
| loader |
| |
| CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_SIZE, |
| CONFIG_SYS_NAND_OOBSIZE, CONFIG_SYS_NAND_BLOCK_SIZE, |
| CONFIG_SYS_NAND_BAD_BLOCK_POS, CFG_SYS_NAND_ECCPOS, |
| CFG_SYS_NAND_ECCSIZE, CFG_SYS_NAND_ECCBYTES |
| Defines the size and behavior of the NAND that SPL uses |
| to read U-Boot |
| |
| CFG_SYS_NAND_U_BOOT_DST |
| Location in memory to load U-Boot to |
| |
| CFG_SYS_NAND_U_BOOT_SIZE |
| Size of image to load |
| |
| CFG_SYS_NAND_U_BOOT_START |
| Entry point in loaded image to jump to |
| |
| CONFIG_SPL_RAM_DEVICE |
| Support for running image already present in ram, in SPL binary |
| |
| CONFIG_SPL_FIT_PRINT |
| Printing information about a FIT image adds quite a bit of |
| code to SPL. So this is normally disabled in SPL. Use this |
| option to re-enable it. This will affect the output of the |
| bootm command when booting a FIT image. |
| |
| - Interrupt support (PPC): |
| |
| There are common interrupt_init() and timer_interrupt() |
| for all PPC archs. interrupt_init() calls interrupt_init_cpu() |
| for CPU specific initialization. interrupt_init_cpu() |
| should set decrementer_count to appropriate value. If |
| CPU resets decrementer automatically after interrupt |
| (ppc4xx) it should set decrementer_count to zero. |
| timer_interrupt() calls timer_interrupt_cpu() for CPU |
| specific handling. If board has watchdog / status_led |
| / other_activity_monitor it works automatically from |
| general timer_interrupt(). |
| |
| |
| Board initialization settings: |
| ------------------------------ |
| |
| During Initialization u-boot calls a number of board specific functions |
| to allow the preparation of board specific prerequisites, e.g. pin setup |
| before drivers are initialized. To enable these callbacks the |
| following configuration macros have to be defined. Currently this is |
| architecture specific, so please check arch/your_architecture/lib/board.c |
| typically in board_init_f() and board_init_r(). |
| |
| - CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f() |
| - CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r() |
| - CONFIG_BOARD_LATE_INIT: Call board_late_init() |
| |
| Configuration Settings: |
| ----------------------- |
| |
| - CONFIG_SYS_LONGHELP: Defined when you want long help messages included; |
| undefine this when you're short of memory. |
| |
| - CFG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default |
| width of the commands listed in the 'help' command output. |
| |
| - CONFIG_SYS_PROMPT: This is what U-Boot prints on the console to |
| prompt for user input. |
| |
| - CFG_SYS_BAUDRATE_TABLE: |
| List of legal baudrate settings for this board. |
| |
| - CFG_SYS_MEM_RESERVE_SECURE |
| Only implemented for ARMv8 for now. |
| If defined, the size of CFG_SYS_MEM_RESERVE_SECURE memory |
| is substracted from total RAM and won't be reported to OS. |
| This memory can be used as secure memory. A variable |
| gd->arch.secure_ram is used to track the location. In systems |
| the RAM base is not zero, or RAM is divided into banks, |
| this variable needs to be recalcuated to get the address. |
| |
| - CFG_SYS_SDRAM_BASE: |
| Physical start address of SDRAM. _Must_ be 0 here. |
| |
| - CFG_SYS_FLASH_BASE: |
| Physical start address of Flash memory. |
| |
| - CONFIG_SYS_MALLOC_LEN: |
| Size of DRAM reserved for malloc() use. |
| |
| - CFG_SYS_BOOTMAPSZ: |
| Maximum size of memory mapped by the startup code of |
| the Linux kernel; all data that must be processed by |
| the Linux kernel (bd_info, boot arguments, FDT blob if |
| used) must be put below this limit, unless "bootm_low" |
| environment variable is defined and non-zero. In such case |
| all data for the Linux kernel must be between "bootm_low" |
| and "bootm_low" + CFG_SYS_BOOTMAPSZ. The environment |
| variable "bootm_mapsize" will override the value of |
| CFG_SYS_BOOTMAPSZ. If CFG_SYS_BOOTMAPSZ is undefined, |
| then the value in "bootm_size" will be used instead. |
| |
| - CONFIG_SYS_BOOT_GET_CMDLINE: |
| Enables allocating and saving kernel cmdline in space between |
| "bootm_low" and "bootm_low" + BOOTMAPSZ. |
| |
| - CONFIG_SYS_BOOT_GET_KBD: |
| Enables allocating and saving a kernel copy of the bd_info in |
| space between "bootm_low" and "bootm_low" + BOOTMAPSZ. |
| |
| - CONFIG_SYS_FLASH_PROTECTION |
| If defined, hardware flash sectors protection is used |
| instead of U-Boot software protection. |
| |
| - CONFIG_SYS_FLASH_CFI: |
| Define if the flash driver uses extra elements in the |
| common flash structure for storing flash geometry. |
| |
| - CONFIG_FLASH_CFI_DRIVER |
| This option also enables the building of the cfi_flash driver |
| in the drivers directory |
| |
| - CONFIG_FLASH_CFI_MTD |
| This option enables the building of the cfi_mtd driver |
| in the drivers directory. The driver exports CFI flash |
| to the MTD layer. |
| |
| - CONFIG_SYS_FLASH_USE_BUFFER_WRITE |
| Use buffered writes to flash. |
| |
| - CONFIG_ENV_FLAGS_LIST_DEFAULT |
| - CFG_ENV_FLAGS_LIST_STATIC |
| Enable validation of the values given to environment variables when |
| calling env set. Variables can be restricted to only decimal, |
| hexadecimal, or boolean. If CONFIG_CMD_NET is also defined, |
| the variables can also be restricted to IP address or MAC address. |
| |
| The format of the list is: |
| type_attribute = [s|d|x|b|i|m] |
| access_attribute = [a|r|o|c] |
| attributes = type_attribute[access_attribute] |
| entry = variable_name[:attributes] |
| list = entry[,list] |
| |
| The type attributes are: |
| s - String (default) |
| d - Decimal |
| x - Hexadecimal |
| b - Boolean ([1yYtT|0nNfF]) |
| i - IP address |
| m - MAC address |
| |
| The access attributes are: |
| a - Any (default) |
| r - Read-only |
| o - Write-once |
| c - Change-default |
| |
| - CONFIG_ENV_FLAGS_LIST_DEFAULT |
| Define this to a list (string) to define the ".flags" |
| environment variable in the default or embedded environment. |
| |
| - CFG_ENV_FLAGS_LIST_STATIC |
| Define this to a list (string) to define validation that |
| should be done if an entry is not found in the ".flags" |
| environment variable. To override a setting in the static |
| list, simply add an entry for the same variable name to the |
| ".flags" variable. |
| |
| If CONFIG_REGEX is defined, the variable_name above is evaluated as a |
| regular expression. This allows multiple variables to define the same |
| flags without explicitly listing them for each variable. |
| |
| The following definitions that deal with the placement and management |
| of environment data (variable area); in general, we support the |
| following configurations: |
| |
| BE CAREFUL! The first access to the environment happens quite early |
| in U-Boot initialization (when we try to get the setting of for the |
| console baudrate). You *MUST* have mapped your NVRAM area then, or |
| U-Boot will hang. |
| |
| Please note that even with NVRAM we still use a copy of the |
| environment in RAM: we could work on NVRAM directly, but we want to |
| keep settings there always unmodified except somebody uses "saveenv" |
| to save the current settings. |
| |
| BE CAREFUL! For some special cases, the local device can not use |
| "saveenv" command. For example, the local device will get the |
| environment stored in a remote NOR flash by SRIO or PCIE link, |
| but it can not erase, write this NOR flash by SRIO or PCIE interface. |
| |
| - CONFIG_NAND_ENV_DST |
| |
| Defines address in RAM to which the nand_spl code should copy the |
| environment. If redundant environment is used, it will be copied to |
| CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE. |
| |
| Please note that the environment is read-only until the monitor |
| has been relocated to RAM and a RAM copy of the environment has been |
| created; also, when using EEPROM you will have to use env_get_f() |
| until then to read environment variables. |
| |
| The environment is protected by a CRC32 checksum. Before the monitor |
| is relocated into RAM, as a result of a bad CRC you will be working |
| with the compiled-in default environment - *silently*!!! [This is |
| necessary, because the first environment variable we need is the |
| "baudrate" setting for the console - if we have a bad CRC, we don't |
| have any device yet where we could complain.] |
| |
| Note: once the monitor has been relocated, then it will complain if |
| the default environment is used; a new CRC is computed as soon as you |
| use the "saveenv" command to store a valid environment. |
| |
| - CONFIG_SYS_FAULT_MII_ADDR: |
| MII address of the PHY to check for the Ethernet link state. |
| |
| - CONFIG_DISPLAY_BOARDINFO |
| Display information about the board that U-Boot is running on |
| when U-Boot starts up. The board function checkboard() is called |
| to do this. |
| |
| - CONFIG_DISPLAY_BOARDINFO_LATE |
| Similar to the previous option, but display this information |
| later, once stdio is running and output goes to the LCD, if |
| present. |
| |
| Low Level (hardware related) configuration options: |
| --------------------------------------------------- |
| |
| - CONFIG_SYS_CACHELINE_SIZE: |
| Cache Line Size of the CPU. |
| |
| - CONFIG_SYS_CCSRBAR_DEFAULT: |
| Default (power-on reset) physical address of CCSR on Freescale |
| PowerPC SOCs. |
| |
| - CFG_SYS_CCSRBAR: |
| Virtual address of CCSR. On a 32-bit build, this is typically |
| the same value as CONFIG_SYS_CCSRBAR_DEFAULT. |
| |
| - CFG_SYS_CCSRBAR_PHYS: |
| Physical address of CCSR. CCSR can be relocated to a new |
| physical address, if desired. In this case, this macro should |
| be set to that address. Otherwise, it should be set to the |
| same value as CONFIG_SYS_CCSRBAR_DEFAULT. For example, CCSR |
| is typically relocated on 36-bit builds. It is recommended |
| that this macro be defined via the _HIGH and _LOW macros: |
| |
| #define CFG_SYS_CCSRBAR_PHYS ((CFG_SYS_CCSRBAR_PHYS_HIGH |
| * 1ull) << 32 | CFG_SYS_CCSRBAR_PHYS_LOW) |
| |
| - CFG_SYS_CCSRBAR_PHYS_HIGH: |
| Bits 33-36 of CFG_SYS_CCSRBAR_PHYS. This value is typically |
| either 0 (32-bit build) or 0xF (36-bit build). This macro is |
| used in assembly code, so it must not contain typecasts or |
| integer size suffixes (e.g. "ULL"). |
| |
| - CFG_SYS_CCSRBAR_PHYS_LOW: |
| Lower 32-bits of CFG_SYS_CCSRBAR_PHYS. This macro is |
| used in assembly code, so it must not contain typecasts or |
| integer size suffixes (e.g. "ULL"). |
| |
| - CONFIG_SYS_IMMR: Physical address of the Internal Memory. |
| DO NOT CHANGE unless you know exactly what you're |
| doing! (11-4) [MPC8xx systems only] |
| |
| - CFG_SYS_INIT_RAM_ADDR: |
| |
| Start address of memory area that can be used for |
| initial data and stack; please note that this must be |
| writable memory that is working WITHOUT special |
| initialization, i. e. you CANNOT use normal RAM which |
| will become available only after programming the |
| memory controller and running certain initialization |
| sequences. |
| |
| U-Boot uses the following memory types: |
| - MPC8xx: IMMR (internal memory of the CPU) |
| |
| - CONFIG_SYS_SCCR: System Clock and reset Control Register (15-27) |
| |
| - CONFIG_SYS_OR_TIMING_SDRAM: |
| SDRAM timing |
| |
| - CONFIG_SYS_SRIOn_MEM_VIRT: |
| Virtual Address of SRIO port 'n' memory region |
| |
| - CONFIG_SYS_SRIOn_MEM_PHYxS: |
| Physical Address of SRIO port 'n' memory region |
| |
| - CONFIG_SYS_SRIOn_MEM_SIZE: |
| Size of SRIO port 'n' memory region |
| |
| - CONFIG_SYS_NAND_BUSWIDTH_16BIT |
| Defined to tell the NAND controller that the NAND chip is using |
| a 16 bit bus. |
| Not all NAND drivers use this symbol. |
| Example of drivers that use it: |
| - drivers/mtd/nand/raw/ndfc.c |
| - drivers/mtd/nand/raw/mxc_nand.c |
| |
| - CONFIG_SYS_NDFC_EBC0_CFG |
| Sets the EBC0_CFG register for the NDFC. If not defined |
| a default value will be used. |
| |
| - CONFIG_SYS_SPD_BUS_NUM |
| If SPD EEPROM is on an I2C bus other than the first |
| one, specify here. Note that the value must resolve |
| to something your driver can deal with. |
| |
| - CONFIG_FSL_DDR_INTERACTIVE |
| Enable interactive DDR debugging. See doc/README.fsl-ddr. |
| |
| - CONFIG_FSL_DDR_SYNC_REFRESH |
| Enable sync of refresh for multiple controllers. |
| |
| - CONFIG_FSL_DDR_BIST |
| Enable built-in memory test for Freescale DDR controllers. |
| |
| - CONFIG_RMII |
| Enable RMII mode for all FECs. |
| Note that this is a global option, we can't |
| have one FEC in standard MII mode and another in RMII mode. |
| |
| - CONFIG_CRC32_VERIFY |
| Add a verify option to the crc32 command. |
| The syntax is: |
| |
| => crc32 -v <address> <count> <crc32> |
| |
| Where address/count indicate a memory area |
| and crc32 is the correct crc32 which the |
| area should have. |
| |
| - CONFIG_LOOPW |
| Add the "loopw" memory command. This only takes effect if |
| the memory commands are activated globally (CONFIG_CMD_MEMORY). |
| |
| - CONFIG_CMD_MX_CYCLIC |
| Add the "mdc" and "mwc" memory commands. These are cyclic |
| "md/mw" commands. |
| Examples: |
| |
| => mdc.b 10 4 500 |
| This command will print 4 bytes (10,11,12,13) each 500 ms. |
| |
| => mwc.l 100 12345678 10 |
| This command will write 12345678 to address 100 all 10 ms. |
| |
| This only takes effect if the memory commands are activated |
| globally (CONFIG_CMD_MEMORY). |
| |
| - CONFIG_SPL_BUILD |
| Set when the currently running compilation is for an artifact |
| that will end up in one of the 'xPL' builds, i.e. SPL, TPL or |
| VPL. Code that needs phase-specific behaviour can check this, |
| or (where possible) use spl_phase() instead. |
| |
| Note that CONFIG_SPL_BUILD *is* always defined when either |
| of CONFIG_TPL_BUILD / CONFIG_VPL_BUILD is defined. This can be |
| counter-intuitive and should perhaps be changed. |
| |
| - CONFIG_TPL_BUILD |
| Set when the currently running compilation is for an artifact |
| that will end up in the TPL build (as opposed to SPL, VPL or |
| U-Boot proper). Code that needs phase-specific behaviour can |
| check this, or (where possible) use spl_phase() instead. |
| |
| - CONFIG_VPL_BUILD |
| Set when the currently running compilation is for an artifact |
| that will end up in the VPL build (as opposed to the SPL, TPL |
| or U-Boot proper). Code that needs phase-specific behaviour can |
| check this, or (where possible) use spl_phase() instead. |
| |
| - CONFIG_ARCH_MAP_SYSMEM |
| Generally U-Boot (and in particular the md command) uses |
| effective address. It is therefore not necessary to regard |
| U-Boot address as virtual addresses that need to be translated |
| to physical addresses. However, sandbox requires this, since |
| it maintains its own little RAM buffer which contains all |
| addressable memory. This option causes some memory accesses |
| to be mapped through map_sysmem() / unmap_sysmem(). |
| |
| - CONFIG_X86_RESET_VECTOR |
| If defined, the x86 reset vector code is included. This is not |
| needed when U-Boot is running from Coreboot. |
| |
| Freescale QE/FMAN Firmware Support: |
| ----------------------------------- |
| |
| The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the |
| loading of "firmware", which is encoded in the QE firmware binary format. |
| This firmware often needs to be loaded during U-Boot booting, so macros |
| are used to identify the storage device (NOR flash, SPI, etc) and the address |
| within that device. |
| |
| - CONFIG_SYS_FMAN_FW_ADDR |
| The address in the storage device where the FMAN microcode is located. The |
| meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro |
| is also specified. |
| |
| - CONFIG_SYS_QE_FW_ADDR |
| The address in the storage device where the QE microcode is located. The |
| meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro |
| is also specified. |
| |
| - CONFIG_SYS_QE_FMAN_FW_LENGTH |
| The maximum possible size of the firmware. The firmware binary format |
| has a field that specifies the actual size of the firmware, but it |
| might not be possible to read any part of the firmware unless some |
| local storage is allocated to hold the entire firmware first. |
| |
| - CONFIG_SYS_QE_FMAN_FW_IN_NOR |
| Specifies that QE/FMAN firmware is located in NOR flash, mapped as |
| normal addressable memory via the LBC. CONFIG_SYS_FMAN_FW_ADDR is the |
| virtual address in NOR flash. |
| |
| - CONFIG_SYS_QE_FMAN_FW_IN_NAND |
| Specifies that QE/FMAN firmware is located in NAND flash. |
| CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash. |
| |
| - CONFIG_SYS_QE_FMAN_FW_IN_MMC |
| Specifies that QE/FMAN firmware is located on the primary SD/MMC |
| device. CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device. |
| |
| - CONFIG_SYS_QE_FMAN_FW_IN_REMOTE |
| Specifies that QE/FMAN firmware is located in the remote (master) |
| memory space. CONFIG_SYS_FMAN_FW_ADDR is a virtual address which |
| can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound |
| window->master inbound window->master LAW->the ucode address in |
| master's memory space. |
| |
| Freescale Layerscape Management Complex Firmware Support: |
| --------------------------------------------------------- |
| The Freescale Layerscape Management Complex (MC) supports the loading of |
| "firmware". |
| This firmware often needs to be loaded during U-Boot booting, so macros |
| are used to identify the storage device (NOR flash, SPI, etc) and the address |
| within that device. |
| |
| - CONFIG_FSL_MC_ENET |
| Enable the MC driver for Layerscape SoCs. |
| |
| Freescale Layerscape Debug Server Support: |
| ------------------------------------------- |
| The Freescale Layerscape Debug Server Support supports the loading of |
| "Debug Server firmware" and triggering SP boot-rom. |
| This firmware often needs to be loaded during U-Boot booting. |
| |
| - CONFIG_SYS_MC_RSV_MEM_ALIGN |
| Define alignment of reserved memory MC requires |
| |
| |
| Building the Software: |
| ====================== |
| |
| Building U-Boot has been tested in several native build environments |
| and in many different cross environments. Of course we cannot support |
| all possibly existing versions of cross development tools in all |
| (potentially obsolete) versions. In case of tool chain problems we |
| recommend to use the ELDK (see https://www.denx.de/wiki/DULG/ELDK) |
| which is extensively used to build and test U-Boot. |
| |
| If you are not using a native environment, it is assumed that you |
| have GNU cross compiling tools available in your path. In this case, |
| you must set the environment variable CROSS_COMPILE in your shell. |
| Note that no changes to the Makefile or any other source files are |
| necessary. For example using the ELDK on a 4xx CPU, please enter: |
| |
| $ CROSS_COMPILE=ppc_4xx- |
| $ export CROSS_COMPILE |
| |
| U-Boot is intended to be simple to build. After installing the |
| sources you must configure U-Boot for one specific board type. This |
| is done by typing: |
| |
| make NAME_defconfig |
| |
| where "NAME_defconfig" is the name of one of the existing configu- |
| rations; see configs/*_defconfig for supported names. |
| |
| Note: for some boards special configuration names may exist; check if |
| additional information is available from the board vendor; for |
| instance, the TQM823L systems are available without (standard) |
| or with LCD support. You can select such additional "features" |
| when choosing the configuration, i. e. |
| |
| make TQM823L_defconfig |
| - will configure for a plain TQM823L, i. e. no LCD support |
| |
| make TQM823L_LCD_defconfig |
| - will configure for a TQM823L with U-Boot console on LCD |
| |
| etc. |
| |
| |
| Finally, type "make all", and you should get some working U-Boot |
| images ready for download to / installation on your system: |
| |
| - "u-boot.bin" is a raw binary image |
| - "u-boot" is an image in ELF binary format |
| - "u-boot.srec" is in Motorola S-Record format |
| |
| User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by |
| setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS. |
| For example to treat all compiler warnings as errors: |
| |
| make KCFLAGS=-Werror |
| |
| Please be aware that the Makefiles assume you are using GNU make, so |
| for instance on NetBSD you might need to use "gmake" instead of |
| native "make". |
| |
| |
| If the system board that you have is not listed, then you will need |
| to port U-Boot to your hardware platform. To do this, follow these |
| steps: |
| |
| 1. Create a new directory to hold your board specific code. Add any |
| files you need. In your board directory, you will need at least |
| the "Makefile" and a "<board>.c". |
| 2. Create a new configuration file "include/configs/<board>.h" for |
| your board. |
| 3. If you're porting U-Boot to a new CPU, then also create a new |
| directory to hold your CPU specific code. Add any files you need. |
| 4. Run "make <board>_defconfig" with your new name. |
| 5. Type "make", and you should get a working "u-boot.srec" file |
| to be installed on your target system. |
| 6. Debug and solve any problems that might arise. |
| [Of course, this last step is much harder than it sounds.] |
| |
| |
| Testing of U-Boot Modifications, Ports to New Hardware, etc.: |
| ============================================================== |
| |
| If you have modified U-Boot sources (for instance added a new board |
| or support for new devices, a new CPU, etc.) you are expected to |
| provide feedback to the other developers. The feedback normally takes |
| the form of a "patch", i.e. a context diff against a certain (latest |
| official or latest in the git repository) version of U-Boot sources. |
| |
| But before you submit such a patch, please verify that your modifi- |
| cation did not break existing code. At least make sure that *ALL* of |
| the supported boards compile WITHOUT ANY compiler warnings. To do so, |
| just run the buildman script (tools/buildman/buildman), which will |
| configure and build U-Boot for ALL supported system. Be warned, this |
| will take a while. Please see the buildman README, or run 'buildman -H' |
| for documentation. |
| |
| |
| See also "U-Boot Porting Guide" below. |
| |
| |
| Monitor Commands - Overview: |
| ============================ |
| |
| go - start application at address 'addr' |
| run - run commands in an environment variable |
| bootm - boot application image from memory |
| bootp - boot image via network using BootP/TFTP protocol |
| bootz - boot zImage from memory |
| tftpboot- boot image via network using TFTP protocol |
| and env variables "ipaddr" and "serverip" |
| (and eventually "gatewayip") |
| tftpput - upload a file via network using TFTP protocol |
| rarpboot- boot image via network using RARP/TFTP protocol |
| diskboot- boot from IDE devicebootd - boot default, i.e., run 'bootcmd' |
| loads - load S-Record file over serial line |
| loadb - load binary file over serial line (kermit mode) |
| loadm - load binary blob from source address to destination address |
| md - memory display |
| mm - memory modify (auto-incrementing) |
| nm - memory modify (constant address) |
| mw - memory write (fill) |
| ms - memory search |
| cp - memory copy |
| cmp - memory compare |
| crc32 - checksum calculation |
| i2c - I2C sub-system |
| sspi - SPI utility commands |
| base - print or set address offset |
| printenv- print environment variables |
| pwm - control pwm channels |
| seama - load SEAMA NAND image |
| setenv - set environment variables |
| saveenv - save environment variables to persistent storage |
| protect - enable or disable FLASH write protection |
| erase - erase FLASH memory |
| flinfo - print FLASH memory information |
| nand - NAND memory operations (see doc/README.nand) |
| bdinfo - print Board Info structure |
| iminfo - print header information for application image |
| coninfo - print console devices and informations |
| ide - IDE sub-system |
| loop - infinite loop on address range |
| loopw - infinite write loop on address range |
| mtest - simple RAM test |
| icache - enable or disable instruction cache |
| dcache - enable or disable data cache |
| reset - Perform RESET of the CPU |
| echo - echo args to console |
| version - print monitor version |
| help - print online help |
| ? - alias for 'help' |
| |
| |
| Monitor Commands - Detailed Description: |
| ======================================== |
| |
| TODO. |
| |
| For now: just type "help <command>". |
| |
| |
| Note for Redundant Ethernet Interfaces: |
| ======================================= |
| |
| Some boards come with redundant Ethernet interfaces; U-Boot supports |
| such configurations and is capable of automatic selection of a |
| "working" interface when needed. MAC assignment works as follows: |
| |
| Network interfaces are numbered eth0, eth1, eth2, ... Corresponding |
| MAC addresses can be stored in the environment as "ethaddr" (=>eth0), |
| "eth1addr" (=>eth1), "eth2addr", ... |
| |
| If the network interface stores some valid MAC address (for instance |
| in SROM), this is used as default address if there is NO correspon- |
| ding setting in the environment; if the corresponding environment |
| variable is set, this overrides the settings in the card; that means: |
| |
| o If the SROM has a valid MAC address, and there is no address in the |
| environment, the SROM's address is used. |
| |
| o If there is no valid address in the SROM, and a definition in the |
| environment exists, then the value from the environment variable is |
| used. |
| |
| o If both the SROM and the environment contain a MAC address, and |
| both addresses are the same, this MAC address is used. |
| |
| o If both the SROM and the environment contain a MAC address, and the |
| addresses differ, the value from the environment is used and a |
| warning is printed. |
| |
| o If neither SROM nor the environment contain a MAC address, an error |
| is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case |
| a random, locally-assigned MAC is used. |
| |
| If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses |
| will be programmed into hardware as part of the initialization process. This |
| may be skipped by setting the appropriate 'ethmacskip' environment variable. |
| The naming convention is as follows: |
| "ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc. |
| |
| Image Formats: |
| ============== |
| |
| U-Boot is capable of booting (and performing other auxiliary operations on) |
| images in two formats: |
| |
| New uImage format (FIT) |
| ----------------------- |
| |
| Flexible and powerful format based on Flattened Image Tree -- FIT (similar |
| to Flattened Device Tree). It allows the use of images with multiple |
| components (several kernels, ramdisks, etc.), with contents protected by |
| SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory. |
| |
| |
| Old uImage format |
| ----------------- |
| |
| Old image format is based on binary files which can be basically anything, |
| preceded by a special header; see the definitions in include/image.h for |
| details; basically, the header defines the following image properties: |
| |
| * Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD, |
| 4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks, |
| LynxOS, pSOS, QNX, RTEMS, INTEGRITY; |
| Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, INTEGRITY). |
| * Target CPU Architecture (Provisions for Alpha, ARM, Intel x86, |
| IA64, MIPS, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit; |
| Currently supported: ARM, Intel x86, MIPS, Nios II, PowerPC). |
| * Compression Type (uncompressed, gzip, bzip2) |
| * Load Address |
| * Entry Point |
| * Image Name |
| * Image Timestamp |
| |
| The header is marked by a special Magic Number, and both the header |
| and the data portions of the image are secured against corruption by |
| CRC32 checksums. |
| |
| |
| Linux Support: |
| ============== |
| |
| Although U-Boot should support any OS or standalone application |
| easily, the main focus has always been on Linux during the design of |
| U-Boot. |
| |
| U-Boot includes many features that so far have been part of some |
| special "boot loader" code within the Linux kernel. Also, any |
| "initrd" images to be used are no longer part of one big Linux image; |
| instead, kernel and "initrd" are separate images. This implementation |
| serves several purposes: |
| |
| - the same features can be used for other OS or standalone |
| applications (for instance: using compressed images to reduce the |
| Flash memory footprint) |
| |
| - it becomes much easier to port new Linux kernel versions because |
| lots of low-level, hardware dependent stuff are done by U-Boot |
| |
| - the same Linux kernel image can now be used with different "initrd" |
| images; of course this also means that different kernel images can |
| be run with the same "initrd". This makes testing easier (you don't |
| have to build a new "zImage.initrd" Linux image when you just |
| change a file in your "initrd"). Also, a field-upgrade of the |
| software is easier now. |
| |
| |
| Linux HOWTO: |
| ============ |
| |
| Porting Linux to U-Boot based systems: |
| --------------------------------------- |
| |
| U-Boot cannot save you from doing all the necessary modifications to |
| configure the Linux device drivers for use with your target hardware |
| (no, we don't intend to provide a full virtual machine interface to |
| Linux :-). |
| |
| But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot). |
| |
| Just make sure your machine specific header file (for instance |
| include/asm-ppc/tqm8xx.h) includes the same definition of the Board |
| Information structure as we define in include/asm-<arch>/u-boot.h, |
| and make sure that your definition of IMAP_ADDR uses the same value |
| as your U-Boot configuration in CONFIG_SYS_IMMR. |
| |
| Note that U-Boot now has a driver model, a unified model for drivers. |
| If you are adding a new driver, plumb it into driver model. If there |
| is no uclass available, you are encouraged to create one. See |
| doc/driver-model. |
| |
| |
| Configuring the Linux kernel: |
| ----------------------------- |
| |
| No specific requirements for U-Boot. Make sure you have some root |
| device (initial ramdisk, NFS) for your target system. |
| |
| |
| Building a Linux Image: |
| ----------------------- |
| |
| With U-Boot, "normal" build targets like "zImage" or "bzImage" are |
| not used. If you use recent kernel source, a new build target |
| "uImage" will exist which automatically builds an image usable by |
| U-Boot. Most older kernels also have support for a "pImage" target, |
| which was introduced for our predecessor project PPCBoot and uses a |
| 100% compatible format. |
| |
| Example: |
| |
| make TQM850L_defconfig |
| make oldconfig |
| make dep |
| make uImage |
| |
| The "uImage" build target uses a special tool (in 'tools/mkimage') to |
| encapsulate a compressed Linux kernel image with header information, |
| CRC32 checksum etc. for use with U-Boot. This is what we are doing: |
| |
| * build a standard "vmlinux" kernel image (in ELF binary format): |
| |
| * convert the kernel into a raw binary image: |
| |
| ${CROSS_COMPILE}-objcopy -O binary \ |
| -R .note -R .comment \ |
| -S vmlinux linux.bin |
| |
| * compress the binary image: |
| |
| gzip -9 linux.bin |
| |
| * package compressed binary image for U-Boot: |
| |
| mkimage -A ppc -O linux -T kernel -C gzip \ |
| -a 0 -e 0 -n "Linux Kernel Image" \ |
| -d linux.bin.gz uImage |
| |
| |
| The "mkimage" tool can also be used to create ramdisk images for use |
| with U-Boot, either separated from the Linux kernel image, or |
| combined into one file. "mkimage" encapsulates the images with a 64 |
| byte header containing information about target architecture, |
| operating system, image type, compression method, entry points, time |
| stamp, CRC32 checksums, etc. |
| |
| "mkimage" can be called in two ways: to verify existing images and |
| print the header information, or to build new images. |
| |
| In the first form (with "-l" option) mkimage lists the information |
| contained in the header of an existing U-Boot image; this includes |
| checksum verification: |
| |
| tools/mkimage -l image |
| -l ==> list image header information |
| |
| The second form (with "-d" option) is used to build a U-Boot image |
| from a "data file" which is used as image payload: |
| |
| tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \ |
| -n name -d data_file image |
| -A ==> set architecture to 'arch' |
| -O ==> set operating system to 'os' |
| -T ==> set image type to 'type' |
| -C ==> set compression type 'comp' |
| -a ==> set load address to 'addr' (hex) |
| -e ==> set entry point to 'ep' (hex) |
| -n ==> set image name to 'name' |
| -d ==> use image data from 'datafile' |
| |
| Right now, all Linux kernels for PowerPC systems use the same load |
| address (0x00000000), but the entry point address depends on the |
| kernel version: |
| |
| - 2.2.x kernels have the entry point at 0x0000000C, |
| - 2.3.x and later kernels have the entry point at 0x00000000. |
| |
| So a typical call to build a U-Boot image would read: |
| |
| -> tools/mkimage -n '2.4.4 kernel for TQM850L' \ |
| > -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \ |
| > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \ |
| > examples/uImage.TQM850L |
| Image Name: 2.4.4 kernel for TQM850L |
| Created: Wed Jul 19 02:34:59 2000 |
| Image Type: PowerPC Linux Kernel Image (gzip compressed) |
| Data Size: 335725 Bytes = 327.86 kB = 0.32 MB |
| Load Address: 0x00000000 |
| Entry Point: 0x00000000 |
| |
| To verify the contents of the image (or check for corruption): |
| |
| -> tools/mkimage -l examples/uImage.TQM850L |
| Image Name: 2.4.4 kernel for TQM850L |
| Created: Wed Jul 19 02:34:59 2000 |
| Image Type: PowerPC Linux Kernel Image (gzip compressed) |
| Data Size: 335725 Bytes = 327.86 kB = 0.32 MB |
| Load Address: 0x00000000 |
| Entry Point: 0x00000000 |
| |
| NOTE: for embedded systems where boot time is critical you can trade |
| speed for memory and install an UNCOMPRESSED image instead: this |
| needs more space in Flash, but boots much faster since it does not |
| need to be uncompressed: |
| |
| -> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz |
| -> tools/mkimage -n '2.4.4 kernel for TQM850L' \ |
| > -A ppc -O linux -T kernel -C none -a 0 -e 0 \ |
| > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \ |
| > examples/uImage.TQM850L-uncompressed |
| Image Name: 2.4.4 kernel for TQM850L |
| Created: Wed Jul 19 02:34:59 2000 |
| Image Type: PowerPC Linux Kernel Image (uncompressed) |
| Data Size: 792160 Bytes = 773.59 kB = 0.76 MB |
| Load Address: 0x00000000 |
| Entry Point: 0x00000000 |
| |
| |
| Similar you can build U-Boot images from a 'ramdisk.image.gz' file |
| when your kernel is intended to use an initial ramdisk: |
| |
| -> tools/mkimage -n 'Simple Ramdisk Image' \ |
| > -A ppc -O linux -T ramdisk -C gzip \ |
| > -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd |
| Image Name: Simple Ramdisk Image |
| Created: Wed Jan 12 14:01:50 2000 |
| Image Type: PowerPC Linux RAMDisk Image (gzip compressed) |
| Data Size: 566530 Bytes = 553.25 kB = 0.54 MB |
| Load Address: 0x00000000 |
| Entry Point: 0x00000000 |
| |
| The "dumpimage" tool can be used to disassemble or list the contents of images |
| built by mkimage. See dumpimage's help output (-h) for details. |
| |
| Installing a Linux Image: |
| ------------------------- |
| |
| To downloading a U-Boot image over the serial (console) interface, |
| you must convert the image to S-Record format: |
| |
| objcopy -I binary -O srec examples/image examples/image.srec |
| |
| The 'objcopy' does not understand the information in the U-Boot |
| image header, so the resulting S-Record file will be relative to |
| address 0x00000000. To load it to a given address, you need to |
| specify the target address as 'offset' parameter with the 'loads' |
| command. |
| |
| Example: install the image to address 0x40100000 (which on the |
| TQM8xxL is in the first Flash bank): |
| |
| => erase 40100000 401FFFFF |
| |
| .......... done |
| Erased 8 sectors |
| |
| => loads 40100000 |
| ## Ready for S-Record download ... |
| ~>examples/image.srec |
| 1 2 3 4 5 6 7 8 9 10 11 12 13 ... |
| ... |
| 15989 15990 15991 15992 |
| [file transfer complete] |
| [connected] |
| ## Start Addr = 0x00000000 |
| |
| |
| You can check the success of the download using the 'iminfo' command; |
| this includes a checksum verification so you can be sure no data |
| corruption happened: |
| |
| => imi 40100000 |
| |
| ## Checking Image at 40100000 ... |
| Image Name: 2.2.13 for initrd on TQM850L |
| Image Type: PowerPC Linux Kernel Image (gzip compressed) |
| Data Size: 335725 Bytes = 327 kB = 0 MB |
| Load Address: 00000000 |
| Entry Point: 0000000c |
| Verifying Checksum ... OK |
| |
| |
| Boot Linux: |
| ----------- |
| |
| The "bootm" command is used to boot an application that is stored in |
| memory (RAM or Flash). In case of a Linux kernel image, the contents |
| of the "bootargs" environment variable is passed to the kernel as |
| parameters. You can check and modify this variable using the |
| "printenv" and "setenv" commands: |
| |
| |
| => printenv bootargs |
| bootargs=root=/dev/ram |
| |
| => setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2 |
| |
| => printenv bootargs |
| bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2 |
| |
| => bootm 40020000 |
| ## Booting Linux kernel at 40020000 ... |
| Image Name: 2.2.13 for NFS on TQM850L |
| Image Type: PowerPC Linux Kernel Image (gzip compressed) |
| Data Size: 381681 Bytes = 372 kB = 0 MB |
| Load Address: 00000000 |
| Entry Point: 0000000c |
| Verifying Checksum ... OK |
| Uncompressing Kernel Image ... OK |
| Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:35:17 MEST 2000 |
| Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2 |
| time_init: decrementer frequency = 187500000/60 |
| Calibrating delay loop... 49.77 BogoMIPS |
| Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000] |
| ... |
| |
| If you want to boot a Linux kernel with initial RAM disk, you pass |
| the memory addresses of both the kernel and the initrd image (PPBCOOT |
| format!) to the "bootm" command: |
| |
| => imi 40100000 40200000 |
| |
| ## Checking Image at 40100000 ... |
| Image Name: 2.2.13 for initrd on TQM850L |
| Image Type: PowerPC Linux Kernel Image (gzip compressed) |
| Data Size: 335725 Bytes = 327 kB = 0 MB |
| Load Address: 00000000 |
| Entry Point: 0000000c |
| Verifying Checksum ... OK |
| |
| ## Checking Image at 40200000 ... |
| Image Name: Simple Ramdisk Image |
| Image Type: PowerPC Linux RAMDisk Image (gzip compressed) |
| Data Size: 566530 Bytes = 553 kB = 0 MB |
| Load Address: 00000000 |
| Entry Point: 00000000 |
| Verifying Checksum ... OK |
| |
| => bootm 40100000 40200000 |
| ## Booting Linux kernel at 40100000 ... |
| Image Name: 2.2.13 for initrd on TQM850L |
| Image Type: PowerPC Linux Kernel Image (gzip compressed) |
| Data Size: 335725 Bytes = 327 kB = 0 MB |
| Load Address: 00000000 |
| Entry Point: 0000000c |
| Verifying Checksum ... OK |
| Uncompressing Kernel Image ... OK |
| ## Loading RAMDisk Image at 40200000 ... |
| Image Name: Simple Ramdisk Image |
| Image Type: PowerPC Linux RAMDisk Image (gzip compressed) |
| Data Size: 566530 Bytes = 553 kB = 0 MB |
| Load Address: 00000000 |
| Entry Point: 00000000 |
| Verifying Checksum ... OK |
| Loading Ramdisk ... OK |
| Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:32:08 MEST 2000 |
| Boot arguments: root=/dev/ram |
| time_init: decrementer frequency = 187500000/60 |
| Calibrating delay loop... 49.77 BogoMIPS |
| ... |
| RAMDISK: Compressed image found at block 0 |
| VFS: Mounted root (ext2 filesystem). |
| |
| bash# |
| |
| Boot Linux and pass a flat device tree: |
| ----------- |
| |
| First, U-Boot must be compiled with the appropriate defines. See the section |
| titled "Linux Kernel Interface" above for a more in depth explanation. The |
| following is an example of how to start a kernel and pass an updated |
| flat device tree: |
| |
| => print oftaddr |
| oftaddr=0x300000 |
| => print oft |
| oft=oftrees/mpc8540ads.dtb |
| => tftp $oftaddr $oft |
| Speed: 1000, full duplex |
| Using TSEC0 device |
| TFTP from server 192.168.1.1; our IP address is 192.168.1.101 |
| Filename 'oftrees/mpc8540ads.dtb'. |
| Load address: 0x300000 |
| Loading: # |
| done |
| Bytes transferred = 4106 (100a hex) |
| => tftp $loadaddr $bootfile |
| Speed: 1000, full duplex |
| Using TSEC0 device |
| TFTP from server 192.168.1.1; our IP address is 192.168.1.2 |
| Filename 'uImage'. |
| Load address: 0x200000 |
| Loading:############ |
| done |
| Bytes transferred = 1029407 (fb51f hex) |
| => print loadaddr |
| loadaddr=200000 |
| => print oftaddr |
| oftaddr=0x300000 |
| => bootm $loadaddr - $oftaddr |
| ## Booting image at 00200000 ... |
| Image Name: Linux-2.6.17-dirty |
| Image Type: PowerPC Linux Kernel Image (gzip compressed) |
| Data Size: 1029343 Bytes = 1005.2 kB |
| Load Address: 00000000 |
| Entry Point: 00000000 |
| Verifying Checksum ... OK |
| Uncompressing Kernel Image ... OK |
| Booting using flat device tree at 0x300000 |
| Using MPC85xx ADS machine description |
| Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb |
| [snip] |
| |
| |
| More About U-Boot Image Types: |
| ------------------------------ |
| |
| U-Boot supports the following image types: |
| |
| "Standalone Programs" are directly runnable in the environment |
| provided by U-Boot; it is expected that (if they behave |
| well) you can continue to work in U-Boot after return from |
| the Standalone Program. |
| "OS Kernel Images" are usually images of some Embedded OS which |
| will take over control completely. Usually these programs |
| will install their own set of exception handlers, device |
| drivers, set up the MMU, etc. - this means, that you cannot |
| expect to re-enter U-Boot except by resetting the CPU. |
| "RAMDisk Images" are more or less just data blocks, and their |
| parameters (address, size) are passed to an OS kernel that is |
| being started. |
| "Multi-File Images" contain several images, typically an OS |
| (Linux) kernel image and one or more data images like |
| RAMDisks. This construct is useful for instance when you want |
| to boot over the network using BOOTP etc., where the boot |
| server provides just a single image file, but you want to get |
| for instance an OS kernel and a RAMDisk image. |
| |
| "Multi-File Images" start with a list of image sizes, each |
| image size (in bytes) specified by an "uint32_t" in network |
| byte order. This list is terminated by an "(uint32_t)0". |
| Immediately after the terminating 0 follow the images, one by |
| one, all aligned on "uint32_t" boundaries (size rounded up to |
| a multiple of 4 bytes). |
| |
| "Firmware Images" are binary images containing firmware (like |
| U-Boot or FPGA images) which usually will be programmed to |
| flash memory. |
| |
| "Script files" are command sequences that will be executed by |
| U-Boot's command interpreter; this feature is especially |
| useful when you configure U-Boot to use a real shell (hush) |
| as command interpreter. |
| |
| Booting the Linux zImage: |
| ------------------------- |
| |
| On some platforms, it's possible to boot Linux zImage. This is done |
| using the "bootz" command. The syntax of "bootz" command is the same |
| as the syntax of "bootm" command. |
| |
| Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply |
| kernel with raw initrd images. The syntax is slightly different, the |
| address of the initrd must be augmented by it's size, in the following |
| format: "<initrd addres>:<initrd size>". |
| |
| |
| Standalone HOWTO: |
| ================= |
| |
| One of the features of U-Boot is that you can dynamically load and |
| run "standalone" applications, which can use some resources of |
| U-Boot like console I/O functions or interrupt services. |
| |
| Two simple examples are included with the sources: |
| |
| "Hello World" Demo: |
| ------------------- |
| |
| 'examples/hello_world.c' contains a small "Hello World" Demo |
| application; it is automatically compiled when you build U-Boot. |
| It's configured to run at address 0x00040004, so you can play with it |
| like that: |
| |
| => loads |
| ## Ready for S-Record download ... |
| ~>examples/hello_world.srec |
| 1 2 3 4 5 6 7 8 9 10 11 ... |
| [file transfer complete] |
| [connected] |
| ## Start Addr = 0x00040004 |
| |
| => go 40004 Hello World! This is a test. |
| ## Starting application at 0x00040004 ... |
| Hello World |
| argc = 7 |
| argv[0] = "40004" |
| argv[1] = "Hello" |
| argv[2] = "World!" |
| argv[3] = "This" |
| argv[4] = "is" |
| argv[5] = "a" |
| argv[6] = "test." |
| argv[7] = "<NULL>" |
| Hit any key to exit ... |
| |
| ## Application terminated, rc = 0x0 |
| |
| Another example, which demonstrates how to register a CPM interrupt |
| handler with the U-Boot code, can be found in 'examples/timer.c'. |
| Here, a CPM timer is set up to generate an interrupt every second. |
| The interrupt service routine is trivial, just printing a '.' |
| character, but this is just a demo program. The application can be |
| controlled by the following keys: |
| |
| ? - print current values og the CPM Timer registers |
| b - enable interrupts and start timer |
| e - stop timer and disable interrupts |
| q - quit application |
| |
| => loads |
| ## Ready for S-Record download ... |
| ~>examples/timer.srec |
| 1 2 3 4 5 6 7 8 9 10 11 ... |
| [file transfer complete] |
| [connected] |
| ## Start Addr = 0x00040004 |
| |
| => go 40004 |
| ## Starting application at 0x00040004 ... |
| TIMERS=0xfff00980 |
| Using timer 1 |
| tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0 |
| |
| Hit 'b': |
| [q, b, e, ?] Set interval 1000000 us |
| Enabling timer |
| Hit '?': |
| [q, b, e, ?] ........ |
| tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0 |
| Hit '?': |
| [q, b, e, ?] . |
| tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0 |
| Hit '?': |
| [q, b, e, ?] . |
| tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0 |
| Hit '?': |
| [q, b, e, ?] . |
| tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0 |
| Hit 'e': |
| [q, b, e, ?] ...Stopping timer |
| Hit 'q': |
| [q, b, e, ?] ## Application terminated, rc = 0x0 |
| |
| |
| Implementation Internals: |
| ========================= |
| |
| The following is not intended to be a complete description of every |
| implementation detail. However, it should help to understand the |
| inner workings of U-Boot and make it easier to port it to custom |
| hardware. |
| |
| |
| Initial Stack, Global Data: |
| --------------------------- |
| |
| The implementation of U-Boot is complicated by the fact that U-Boot |
| starts running out of ROM (flash memory), usually without access to |
| system RAM (because the memory controller is not initialized yet). |
| This means that we don't have writable Data or BSS segments, and BSS |
| is not initialized as zero. To be able to get a C environment working |
| at all, we have to allocate at least a minimal stack. Implementation |
| options for this are defined and restricted by the CPU used: Some CPU |
| models provide on-chip memory (like the IMMR area on MPC8xx and |
| MPC826x processors), on others (parts of) the data cache can be |
| locked as (mis-) used as memory, etc. |
| |
| Chris Hallinan posted a good summary of these issues to the |
| U-Boot mailing list: |
| |
| Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)? |
| From: "Chris Hallinan" <clh@net1plus.com> |
| Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET) |
| ... |
| |
| Correct me if I'm wrong, folks, but the way I understand it |
| is this: Using DCACHE as initial RAM for Stack, etc, does not |
| require any physical RAM backing up the cache. The cleverness |
| is that the cache is being used as a temporary supply of |
| necessary storage before the SDRAM controller is setup. It's |
| beyond the scope of this list to explain the details, but you |
| can see how this works by studying the cache architecture and |
| operation in the architecture and processor-specific manuals. |
| |
| OCM is On Chip Memory, which I believe the 405GP has 4K. It |
| is another option for the system designer to use as an |
| initial stack/RAM area prior to SDRAM being available. Either |
| option should work for you. Using CS 4 should be fine if your |
| board designers haven't used it for something that would |
| cause you grief during the initial boot! It is frequently not |
| used. |
| |
| CFG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere |
| with your processor/board/system design. The default value |
| you will find in any recent u-boot distribution in |
| walnut.h should work for you. I'd set it to a value larger |
| than your SDRAM module. If you have a 64MB SDRAM module, set |
| it above 400_0000. Just make sure your board has no resources |
| that are supposed to respond to that address! That code in |
| start.S has been around a while and should work as is when |
| you get the config right. |
| |
| -Chris Hallinan |
| DS4.COM, Inc. |
| |
| It is essential to remember this, since it has some impact on the C |
| code for the initialization procedures: |
| |
| * Initialized global data (data segment) is read-only. Do not attempt |
| to write it. |
| |
| * Do not use any uninitialized global data (or implicitly initialized |
| as zero data - BSS segment) at all - this is undefined, initiali- |
| zation is performed later (when relocating to RAM). |
| |
| * Stack space is very limited. Avoid big data buffers or things like |
| that. |
| |
| Having only the stack as writable memory limits means we cannot use |
| normal global data to share information between the code. But it |
| turned out that the implementation of U-Boot can be greatly |
| simplified by making a global data structure (gd_t) available to all |
| functions. We could pass a pointer to this data as argument to _all_ |
| functions, but this would bloat the code. Instead we use a feature of |
| the GCC compiler (Global Register Variables) to share the data: we |
| place a pointer (gd) to the global data into a register which we |
| reserve for this purpose. |
| |
| When choosing a register for such a purpose we are restricted by the |
| relevant (E)ABI specifications for the current architecture, and by |
| GCC's implementation. |
| |
| For PowerPC, the following registers have specific use: |
| R1: stack pointer |
| R2: reserved for system use |
| R3-R4: parameter passing and return values |
| R5-R10: parameter passing |
| R13: small data area pointer |
| R30: GOT pointer |
| R31: frame pointer |
| |
| (U-Boot also uses R12 as internal GOT pointer. r12 |
| is a volatile register so r12 needs to be reset when |
| going back and forth between asm and C) |
| |
| ==> U-Boot will use R2 to hold a pointer to the global data |
| |
| Note: on PPC, we could use a static initializer (since the |
| address of the global data structure is known at compile time), |
| but it turned out that reserving a register results in somewhat |
| smaller code - although the code savings are not that big (on |
| average for all boards 752 bytes for the whole U-Boot image, |
| 624 text + 127 data). |
| |
| On ARM, the following registers are used: |
| |
| R0: function argument word/integer result |
| R1-R3: function argument word |
| R9: platform specific |
| R10: stack limit (used only if stack checking is enabled) |
| R11: argument (frame) pointer |
| R12: temporary workspace |
| R13: stack pointer |
| R14: link register |
| R15: program counter |
| |
| ==> U-Boot will use R9 to hold a pointer to the global data |
| |
| Note: on ARM, only R_ARM_RELATIVE relocations are supported. |
| |
| On Nios II, the ABI is documented here: |
| https://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf |
| |
| ==> U-Boot will use gp to hold a pointer to the global data |
| |
| Note: on Nios II, we give "-G0" option to gcc and don't use gp |
| to access small data sections, so gp is free. |
| |
| On RISC-V, the following registers are used: |
| |
| x0: hard-wired zero (zero) |
| x1: return address (ra) |
| x2: stack pointer (sp) |
| x3: global pointer (gp) |
| x4: thread pointer (tp) |
| x5: link register (t0) |
| x8: frame pointer (fp) |
| x10-x11: arguments/return values (a0-1) |
| x12-x17: arguments (a2-7) |
| x28-31: temporaries (t3-6) |
| pc: program counter (pc) |
| |
| ==> U-Boot will use gp to hold a pointer to the global data |
| |
| Memory Management: |
| ------------------ |
| |
| U-Boot runs in system state and uses physical addresses, i.e. the |
| MMU is not used either for address mapping nor for memory protection. |
| |
| The available memory is mapped to fixed addresses using the memory |
| controller. In this process, a contiguous block is formed for each |
| memory type (Flash, SDRAM, SRAM), even when it consists of several |
| physical memory banks. |
| |
| U-Boot is installed in the first 128 kB of the first Flash bank (on |
| TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After |
| booting and sizing and initializing DRAM, the code relocates itself |
| to the upper end of DRAM. Immediately below the U-Boot code some |
| memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN |
| configuration setting]. Below that, a structure with global Board |
| Info data is placed, followed by the stack (growing downward). |
| |
| Additionally, some exception handler code is copied to the low 8 kB |
| of DRAM (0x00000000 ... 0x00001FFF). |
| |
| So a typical memory configuration with 16 MB of DRAM could look like |
| this: |
| |
| 0x0000 0000 Exception Vector code |
| : |
| 0x0000 1FFF |
| 0x0000 2000 Free for Application Use |
| : |
| : |
| |
| : |
| : |
| 0x00FB FF20 Monitor Stack (Growing downward) |
| 0x00FB FFAC Board Info Data and permanent copy of global data |
| 0x00FC 0000 Malloc Arena |
| : |
| 0x00FD FFFF |
| 0x00FE 0000 RAM Copy of Monitor Code |
| ... eventually: LCD or video framebuffer |
| ... eventually: pRAM (Protected RAM - unchanged by reset) |
| 0x00FF FFFF [End of RAM] |
| |
| |
| System Initialization: |
| ---------------------- |
| |
| In the reset configuration, U-Boot starts at the reset entry point |
| (on most PowerPC systems at address 0x00000100). Because of the reset |
| configuration for CS0# this is a mirror of the on board Flash memory. |
| To be able to re-map memory U-Boot then jumps to its link address. |
| To be able to implement the initialization code in C, a (small!) |
| initial stack is set up in the internal Dual Ported RAM (in case CPUs |
| which provide such a feature like), or in a locked part of the data |
| cache. After that, U-Boot initializes the CPU core, the caches and |
| the SIU. |
| |
| Next, all (potentially) available memory banks are mapped using a |
| preliminary mapping. For example, we put them on 512 MB boundaries |
| (multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash |
| on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is |
| programmed for SDRAM access. Using the temporary configuration, a |
| simple memory test is run that determines the size of the SDRAM |
| banks. |
| |
| When there is more than one SDRAM bank, and the banks are of |
| different size, the largest is mapped first. For equal size, the first |
| bank (CS2#) is mapped first. The first mapping is always for address |
| 0x00000000, with any additional banks following immediately to create |
| contiguous memory starting from 0. |
| |
| Then, the monitor installs itself at the upper end of the SDRAM area |
| and allocates memory for use by malloc() and for the global Board |
| Info data; also, the exception vector code is copied to the low RAM |
| pages, and the final stack is set up. |
| |
| Only after this relocation will you have a "normal" C environment; |
| until that you are restricted in several ways, mostly because you are |
| running from ROM, and because the code will have to be relocated to a |
| new address in RAM. |
| |
| |
| Contributing |
| ============ |
| |
| The U-Boot projects depends on contributions from the user community. |
| If you want to participate, please, have a look at the 'General' |
| section of https://docs.u-boot.org/en/latest/develop/index.html |
| where we describe coding standards and the patch submission process. |