mirror of
https://github.com/brain-hackers/u-boot-brain
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9c5feab76f
The purpose of .globl is to export symbols for ld, not to declare external symbols. By the way, use the ENTRY() and ENDPROC() macros to define functions rather than using .global directly. Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
154 lines
4.8 KiB
ArmAsm
154 lines
4.8 KiB
ArmAsm
/*
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* crt0 - C-runtime startup Code for ARM U-Boot
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*
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* Copyright (c) 2012 Albert ARIBAUD <albert.u.boot@aribaud.net>
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*
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* See file CREDITS for list of people who contributed to this
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* project.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of
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* the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
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* MA 02111-1307 USA
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*/
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#include <config.h>
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#include <asm-offsets.h>
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#include <linux/linkage.h>
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/*
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* This file handles the target-independent stages of the U-Boot
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* start-up where a C runtime environment is needed. Its entry point
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* is _main and is branched into from the target's start.S file.
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*
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* _main execution sequence is:
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*
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* 1. Set up initial environment for calling board_init_f().
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* This environment only provides a stack and a place to store
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* the GD ('global data') structure, both located in some readily
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* available RAM (SRAM, locked cache...). In this context, VARIABLE
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* global data, initialized or not (BSS), are UNAVAILABLE; only
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* CONSTANT initialized data are available.
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*
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* 2. Call board_init_f(). This function prepares the hardware for
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* execution from system RAM (DRAM, DDR...) As system RAM may not
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* be available yet, , board_init_f() must use the current GD to
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* store any data which must be passed on to later stages. These
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* data include the relocation destination, the future stack, and
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* the future GD location.
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*
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* (the following applies only to non-SPL builds)
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*
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* 3. Set up intermediate environment where the stack and GD are the
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* ones allocated by board_init_f() in system RAM, but BSS and
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* initialized non-const data are still not available.
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*
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* 4. Call relocate_code(). This function relocates U-Boot from its
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* current location into the relocation destination computed by
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* board_init_f().
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*
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* 5. Set up final environment for calling board_init_r(). This
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* environment has BSS (initialized to 0), initialized non-const
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* data (initialized to their intended value), and stack in system
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* RAM. GD has retained values set by board_init_f(). Some CPUs
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* have some work left to do at this point regarding memory, so
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* call c_runtime_cpu_setup.
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*
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* 6. Branch to either nand_boot() or board_init_r().
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*/
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/*
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* entry point of crt0 sequence
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*/
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ENTRY(_main)
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/*
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* Set up initial C runtime environment and call board_init_f(0).
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*/
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#if defined(CONFIG_NAND_SPL)
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/* deprecated, use instead CONFIG_SPL_BUILD */
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ldr sp, =(CONFIG_SYS_INIT_SP_ADDR)
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#elif defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK)
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ldr sp, =(CONFIG_SPL_STACK)
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#else
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ldr sp, =(CONFIG_SYS_INIT_SP_ADDR)
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#endif
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bic sp, sp, #7 /* 8-byte alignment for ABI compliance */
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sub sp, #GD_SIZE /* allocate one GD above SP */
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bic sp, sp, #7 /* 8-byte alignment for ABI compliance */
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mov r8, sp /* GD is above SP */
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mov r0, #0
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bl board_init_f
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#if ! defined(CONFIG_SPL_BUILD)
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/*
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* Set up intermediate environment (new sp and gd) and call
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* relocate_code(addr_sp, gd, addr_moni). Trick here is that
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* we'll return 'here' but relocated.
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*/
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ldr sp, [r8, #GD_START_ADDR_SP] /* r8 = gd->start_addr_sp */
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bic sp, sp, #7 /* 8-byte alignment for ABI compliance */
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ldr r8, [r8, #GD_BD] /* r8 = gd->bd */
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sub r8, r8, #GD_SIZE /* new GD is below bd */
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adr lr, here
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ldr r0, [r8, #GD_RELOC_OFF] /* lr = gd->start_addr_sp */
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add lr, lr, r0
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ldr r0, [r8, #GD_START_ADDR_SP] /* r0 = gd->start_addr_sp */
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mov r1, r8 /* r1 = gd */
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ldr r2, [r8, #GD_RELOCADDR] /* r2 = gd->relocaddr */
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b relocate_code
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here:
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/* Set up final (full) environment */
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bl c_runtime_cpu_setup /* we still call old routine here */
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ldr r0, =__bss_start /* this is auto-relocated! */
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ldr r1, =__bss_end /* this is auto-relocated! */
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mov r2, #0x00000000 /* prepare zero to clear BSS */
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clbss_l:cmp r0, r1 /* while not at end of BSS */
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strlo r2, [r0] /* clear 32-bit BSS word */
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addlo r0, r0, #4 /* move to next */
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blo clbss_l
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bl coloured_LED_init
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bl red_led_on
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#if defined(CONFIG_NAND_SPL)
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/* call _nand_boot() */
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ldr pc, =nand_boot
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#else
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/* call board_init_r(gd_t *id, ulong dest_addr) */
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mov r0, r8 /* gd_t */
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ldr r1, [r8, #GD_RELOCADDR] /* dest_addr */
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/* call board_init_r */
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ldr pc, =board_init_r /* this is auto-relocated! */
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#endif
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/* we should not return here. */
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#endif
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ENDPROC(_main)
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