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Diffstat (limited to 'arch/arm/lib/crt0.S')
| -rw-r--r-- | arch/arm/lib/crt0.S | 139 |
1 files changed, 139 insertions, 0 deletions
diff --git a/arch/arm/lib/crt0.S b/arch/arm/lib/crt0.S new file mode 100644 index 0000000..a5bffb8 --- /dev/null +++ b/arch/arm/lib/crt0.S @@ -0,0 +1,139 @@ +/* + * crt0 - C-runtime startup Code for ARM U-Boot + * + * Copyright (c) 2012 Albert ARIBAUD <albert.u.boot@aribaud.net> + * + * See file CREDITS for list of people who contributed to this + * project. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License as + * published by the Free Software Foundation; either version 2 of + * the License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, + * MA 02111-1307 USA + */ + +#include <config.h> +#include <asm-offsets.h> +#include <linux/linkage.h> + +/* + * This file handles the target-independent stages of the U-Boot + * start-up where a C runtime environment is needed. Its entry point + * is _main and is branched into from the target's start.S file. + * + * _main execution sequence is: + * + * 1. Set up initial environment for calling board_init_f(). + * This environment only provides a stack and a place to store + * the GD ('global data') structure, both located in some readily + * available RAM (SRAM, locked cache...). In this context, VARIABLE + * global data, initialized or not (BSS), are UNAVAILABLE; only + * CONSTANT initialized data are available. + * + * 2. Call board_init_f(). This function prepares the hardware for + * execution from system RAM (DRAM, DDR...) As system RAM may not + * be available yet, , board_init_f() must use the current GD to + * store any data which must be passed on to later stages. These + * data include the relocation destination, the future stack, and + * the future GD location. + * + * (the following applies only to non-SPL builds) + * + * 3. Set up intermediate environment where the stack and GD are the + * ones allocated by board_init_f() in system RAM, but BSS and + * initialized non-const data are still not available. + * + * 4. Call relocate_code(). This function relocates U-Boot from its + * current location into the relocation destination computed by + * board_init_f(). + * + * 5. Set up final environment for calling board_init_r(). This + * environment has BSS (initialized to 0), initialized non-const + * data (initialized to their intended value), and stack in system + * RAM. GD has retained values set by board_init_f(). Some CPUs + * have some work left to do at this point regarding memory, so + * call c_runtime_cpu_setup. + * + * 6. Branch to board_init_r(). + */ + +/* + * entry point of crt0 sequence + */ + +ENTRY(_main) + +/* + * Set up initial C runtime environment and call board_init_f(0). + */ + +#if defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK) + ldr sp, =(CONFIG_SPL_STACK) +#else + ldr sp, =(CONFIG_SYS_INIT_SP_ADDR) +#endif + bic sp, sp, #7 /* 8-byte alignment for ABI compliance */ + sub sp, #GD_SIZE /* allocate one GD above SP */ + bic sp, sp, #7 /* 8-byte alignment for ABI compliance */ + mov r8, sp /* GD is above SP */ + mov r0, #0 + bl board_init_f + +#if ! defined(CONFIG_SPL_BUILD) + +/* + * Set up intermediate environment (new sp and gd) and call + * relocate_code(addr_moni). Trick here is that we'll return + * 'here' but relocated. + */ + + ldr sp, [r8, #GD_START_ADDR_SP] /* sp = gd->start_addr_sp */ + bic sp, sp, #7 /* 8-byte alignment for ABI compliance */ + ldr r8, [r8, #GD_BD] /* r8 = gd->bd */ + sub r8, r8, #GD_SIZE /* new GD is below bd */ + + adr lr, here + ldr r0, [r8, #GD_RELOC_OFF] /* r0 = gd->reloc_off */ + add lr, lr, r0 + ldr r0, [r8, #GD_RELOCADDR] /* r0 = gd->relocaddr */ + b relocate_code +here: + +/* Set up final (full) environment */ + + bl c_runtime_cpu_setup /* we still call old routine here */ + + ldr r0, =__bss_start /* this is auto-relocated! */ + ldr r1, =__bss_end /* this is auto-relocated! */ + + mov r2, #0x00000000 /* prepare zero to clear BSS */ + +clbss_l:cmp r0, r1 /* while not at end of BSS */ + strlo r2, [r0] /* clear 32-bit BSS word */ + addlo r0, r0, #4 /* move to next */ + blo clbss_l + + bl coloured_LED_init + bl red_led_on + + /* call board_init_r(gd_t *id, ulong dest_addr) */ + mov r0, r8 /* gd_t */ + ldr r1, [r8, #GD_RELOCADDR] /* dest_addr */ + /* call board_init_r */ + ldr pc, =board_init_r /* this is auto-relocated! */ + + /* we should not return here. */ + +#endif + +ENDPROC(_main) |
