| David Feng | 85fd5f1 | 2013-12-14 11:47:35 +0800 | [diff] [blame] | 1 | /* |
| 2 | * crt0 - C-runtime startup Code for AArch64 U-Boot |
| 3 | * |
| 4 | * (C) Copyright 2013 |
| 5 | * David Feng <fenghua@phytium.com.cn> |
| 6 | * |
| 7 | * (C) Copyright 2012 |
| 8 | * Albert ARIBAUD <albert.u.boot@aribaud.net> |
| 9 | * |
| 10 | * SPDX-License-Identifier: GPL-2.0+ |
| 11 | */ |
| 12 | |
| 13 | #include <config.h> |
| 14 | #include <asm-offsets.h> |
| 15 | #include <asm/macro.h> |
| 16 | #include <linux/linkage.h> |
| 17 | |
| 18 | /* |
| 19 | * This file handles the target-independent stages of the U-Boot |
| 20 | * start-up where a C runtime environment is needed. Its entry point |
| 21 | * is _main and is branched into from the target's start.S file. |
| 22 | * |
| 23 | * _main execution sequence is: |
| 24 | * |
| 25 | * 1. Set up initial environment for calling board_init_f(). |
| 26 | * This environment only provides a stack and a place to store |
| 27 | * the GD ('global data') structure, both located in some readily |
| 28 | * available RAM (SRAM, locked cache...). In this context, VARIABLE |
| 29 | * global data, initialized or not (BSS), are UNAVAILABLE; only |
| 30 | * CONSTANT initialized data are available. |
| 31 | * |
| 32 | * 2. Call board_init_f(). This function prepares the hardware for |
| 33 | * execution from system RAM (DRAM, DDR...) As system RAM may not |
| 34 | * be available yet, , board_init_f() must use the current GD to |
| 35 | * store any data which must be passed on to later stages. These |
| 36 | * data include the relocation destination, the future stack, and |
| 37 | * the future GD location. |
| 38 | * |
| 39 | * (the following applies only to non-SPL builds) |
| 40 | * |
| 41 | * 3. Set up intermediate environment where the stack and GD are the |
| 42 | * ones allocated by board_init_f() in system RAM, but BSS and |
| 43 | * initialized non-const data are still not available. |
| 44 | * |
| 45 | * 4. Call relocate_code(). This function relocates U-Boot from its |
| 46 | * current location into the relocation destination computed by |
| 47 | * board_init_f(). |
| 48 | * |
| 49 | * 5. Set up final environment for calling board_init_r(). This |
| 50 | * environment has BSS (initialized to 0), initialized non-const |
| 51 | * data (initialized to their intended value), and stack in system |
| 52 | * RAM. GD has retained values set by board_init_f(). Some CPUs |
| 53 | * have some work left to do at this point regarding memory, so |
| 54 | * call c_runtime_cpu_setup. |
| 55 | * |
| 56 | * 6. Branch to board_init_r(). |
| 57 | */ |
| 58 | |
| 59 | ENTRY(_main) |
| 60 | |
| 61 | /* |
| 62 | * Set up initial C runtime environment and call board_init_f(0). |
| 63 | */ |
| 64 | ldr x0, =(CONFIG_SYS_INIT_SP_ADDR) |
| 65 | sub x0, x0, #GD_SIZE /* allocate one GD above SP */ |
| 66 | bic sp, x0, #0xf /* 16-byte alignment for ABI compliance */ |
| 67 | mov x18, sp /* GD is above SP */ |
| 68 | mov x0, #0 |
| 69 | bl board_init_f |
| 70 | |
| 71 | /* |
| 72 | * Set up intermediate environment (new sp and gd) and call |
| 73 | * relocate_code(addr_moni). Trick here is that we'll return |
| 74 | * 'here' but relocated. |
| 75 | */ |
| 76 | ldr x0, [x18, #GD_START_ADDR_SP] /* x0 <- gd->start_addr_sp */ |
| 77 | bic sp, x0, #0xf /* 16-byte alignment for ABI compliance */ |
| 78 | ldr x18, [x18, #GD_BD] /* x18 <- gd->bd */ |
| 79 | sub x18, x18, #GD_SIZE /* new GD is below bd */ |
| 80 | |
| 81 | adr lr, relocation_return |
| 82 | ldr x9, [x18, #GD_RELOC_OFF] /* x9 <- gd->reloc_off */ |
| 83 | add lr, lr, x9 /* new return address after relocation */ |
| 84 | ldr x0, [x18, #GD_RELOCADDR] /* x0 <- gd->relocaddr */ |
| 85 | b relocate_code |
| 86 | |
| 87 | relocation_return: |
| 88 | |
| 89 | /* |
| 90 | * Set up final (full) environment |
| 91 | */ |
| 92 | bl c_runtime_cpu_setup /* still call old routine */ |
| 93 | |
| 94 | /* |
| 95 | * Clear BSS section |
| 96 | */ |
| 97 | ldr x0, =__bss_start /* this is auto-relocated! */ |
| 98 | ldr x1, =__bss_end /* this is auto-relocated! */ |
| 99 | mov x2, #0 |
| 100 | clear_loop: |
| 101 | str x2, [x0] |
| 102 | add x0, x0, #8 |
| 103 | cmp x0, x1 |
| 104 | b.lo clear_loop |
| 105 | |
| 106 | /* call board_init_r(gd_t *id, ulong dest_addr) */ |
| 107 | mov x0, x18 /* gd_t */ |
| 108 | ldr x1, [x18, #GD_RELOCADDR] /* dest_addr */ |
| 109 | b board_init_r /* PC relative jump */ |
| 110 | |
| 111 | /* NOTREACHED - board_init_r() does not return */ |
| 112 | |
| 113 | ENDPROC(_main) |