mirror of
https://github.com/AsahiLinux/u-boot
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139 lines
4.5 KiB
ArmAsm
139 lines
4.5 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 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_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_moni). Trick here is that we'll return
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* 'here' but relocated.
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*/
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ldr sp, [r8, #GD_START_ADDR_SP] /* sp = 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] /* r0 = gd->reloc_off */
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add lr, lr, r0
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ldr r0, [r8, #GD_RELOCADDR] /* r0 = 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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/* 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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/* we should not return here. */
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#endif
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ENDPROC(_main)
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