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* crt0 - C-runtime startup Code for ARM U-Boot
* Copyright (c) 2012 Albert ARIBAUD <>
* 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
* 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>
* 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 either nand_boot() or board_init_r().
* declare nand_boot() or board_init_r() to jump to at end of crt0
#if defined(CONFIG_NAND_SPL)
.globl nand_boot
#elif ! defined(CONFIG_SPL_BUILD)
.globl board_init_r
* start and end of BSS
.globl __bss_start
.globl __bss_end__
* entry point of crt0 sequence
.globl _board_init_f_link_addr
.word board_init_f
.globl _start_link_val2
.word _main
.global _main
* Set up initial C runtime environment and call board_init_f(0).
#if defined(CONFIG_NAND_SPL)
/* deprecated, use instead CONFIG_SPL_BUILD */
#elif defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK)
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
/* Instead of 'bl' use 'ldr pc, addr'
* Rationale: 'bl' is PC-relative, => not appropriate when running
* from Flash, because .text is already copied into RAM, so, flow has
* to jump to RAM (meaning: linker-based symbol address).
mov r14, pc
ldr pc, _board_init_f_link_addr
bl board_init_f
#if ! defined(CONFIG_SPL_BUILD)
* Set up intermediate environment (new sp and gd) and call
* relocate_code(addr_sp, gd, addr_moni). Trick here is that
* we'll return 'here' but relocated.
ldr sp, [r8, #GD_START_ADDR_SP] /* r8 = 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
/* additional test if running from flash (FPGA) */
adr r0, _main /* r0 <- current position of code */
ldr r1, _start_link_val2 /* r1 = current position offset relative to code start :test if we run from flash or RAM */
cmp r0, r1 /* if not equal we run from FLASH -> r14 offset correction needed */
beq no_correction
sub r0, r0, r1 /* r0 = flash base */
sub r14, r14, r0 /* r14 = fixed return address after code relocation */
/* additional test if running from flash (FPGA) */
ldr r0, [r8, #GD_RELOC_OFF] /* lr = gd->start_addr_sp */
add lr, lr, r0
ldr r0, [r8, #GD_START_ADDR_SP] /* r0 = gd->start_addr_sp */
mov r1, r8 /* r1 = gd */
ldr r2, [r8, #GD_RELOCADDR] /* r2 = gd->relocaddr */
b relocate_code
/* 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
#if defined(CONFIG_NAND_SPL)
/* call _nand_boot() */
ldr pc, =nand_boot
/* 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. */