| Thomas Chou | 47eae23 | 2015-11-07 14:31:08 +0800 | [diff] [blame] | 1 | CFI or JEDEC memory-mapped NOR flash, MTD-RAM (NVRAM...) |
| 2 | |
| 3 | Flash chips (Memory Technology Devices) are often used for solid state |
| 4 | file systems on embedded devices. |
| 5 | |
| 6 | - compatible : should contain the specific model of mtd chip(s) |
| 7 | used, if known, followed by either "cfi-flash", "jedec-flash", |
| 8 | "mtd-ram" or "mtd-rom". |
| 9 | - reg : Address range(s) of the mtd chip(s) |
| 10 | It's possible to (optionally) define multiple "reg" tuples so that |
| 11 | non-identical chips can be described in one node. |
| 12 | - bank-width : Width (in bytes) of the bank. Equal to the |
| 13 | device width times the number of interleaved chips. |
| 14 | - device-width : (optional) Width of a single mtd chip. If |
| 15 | omitted, assumed to be equal to 'bank-width'. |
| 16 | - #address-cells, #size-cells : Must be present if the device has |
| 17 | sub-nodes representing partitions (see below). In this case |
| 18 | both #address-cells and #size-cells must be equal to 1. |
| 19 | - no-unaligned-direct-access: boolean to disable the default direct |
| 20 | mapping of the flash. |
| 21 | On some platforms (e.g. MPC5200) a direct 1:1 mapping may cause |
| 22 | problems with JFFS2 usage, as the local bus (LPB) doesn't support |
| 23 | unaligned accesses as implemented in the JFFS2 code via memcpy(). |
| 24 | By defining "no-unaligned-direct-access", the flash will not be |
| 25 | exposed directly to the MTD users (e.g. JFFS2) any more. |
| 26 | - linux,mtd-name: allow to specify the mtd name for retro capability with |
| 27 | physmap-flash drivers as boot loader pass the mtd partition via the old |
| 28 | device name physmap-flash. |
| 29 | - use-advanced-sector-protection: boolean to enable support for the |
| 30 | advanced sector protection (Spansion: PPB - Persistent Protection |
| 31 | Bits) locking. |
| 32 | |
| 33 | For JEDEC compatible devices, the following additional properties |
| 34 | are defined: |
| 35 | |
| 36 | - vendor-id : Contains the flash chip's vendor id (1 byte). |
| 37 | - device-id : Contains the flash chip's device id (1 byte). |
| 38 | |
| 39 | For ROM compatible devices (and ROM fallback from cfi-flash), the following |
| 40 | additional (optional) property is defined: |
| 41 | |
| 42 | - erase-size : The chip's physical erase block size in bytes. |
| 43 | |
| 44 | The device tree may optionally contain sub-nodes describing partitions of the |
| 45 | address space. See partition.txt for more detail. |
| 46 | |
| 47 | Example: |
| 48 | |
| 49 | flash@ff000000 { |
| 50 | compatible = "amd,am29lv128ml", "cfi-flash"; |
| 51 | reg = <ff000000 01000000>; |
| 52 | bank-width = <4>; |
| 53 | device-width = <1>; |
| 54 | #address-cells = <1>; |
| 55 | #size-cells = <1>; |
| 56 | fs@0 { |
| 57 | label = "fs"; |
| 58 | reg = <0 f80000>; |
| 59 | }; |
| 60 | firmware@f80000 { |
| 61 | label ="firmware"; |
| 62 | reg = <f80000 80000>; |
| 63 | read-only; |
| 64 | }; |
| 65 | }; |
| 66 | |
| 67 | Here an example with multiple "reg" tuples: |
| 68 | |
| 69 | flash@f0000000,0 { |
| 70 | #address-cells = <1>; |
| 71 | #size-cells = <1>; |
| 72 | compatible = "intel,pc48f4400p0vb", "cfi-flash"; |
| 73 | reg = <0 0x00000000 0x02000000 |
| 74 | 0 0x02000000 0x02000000>; |
| 75 | bank-width = <2>; |
| 76 | partition@0 { |
| 77 | label = "test-part1"; |
| 78 | reg = <0 0x04000000>; |
| 79 | }; |
| 80 | }; |
| 81 | |
| 82 | An example using SRAM: |
| 83 | |
| 84 | sram@2,0 { |
| 85 | compatible = "samsung,k6f1616u6a", "mtd-ram"; |
| 86 | reg = <2 0 0x00200000>; |
| 87 | bank-width = <2>; |
| 88 | }; |