203 lines
5.7 KiB
ArmAsm
203 lines
5.7 KiB
ArmAsm
/* SPDX-License-Identifier: GPL-2.0+ */
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/*
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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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#include <config.h>
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#include <asm-offsets.h>
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#include <linux/linkage.h>
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#include <asm/assembler.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. GD should be zeroed
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* before board_init_f() is called.
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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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* 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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* 4a.For U-Boot proper (not SPL), call relocate_code(). This function
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* relocates U-Boot from its current location into the relocation
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* destination computed by board_init_f().
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*
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* 4b.For SPL, board_init_f() just returns (to crt0). There is no
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* code relocation in SPL.
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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 (for SPL moving the stack and GD into RAM is optional - see
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* CONFIG_SPL_STACK_R). GD has retained values set by board_init_f().
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*
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* 6. For U-Boot proper (not SPL), some CPUs have some work left to do
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* at this point regarding memory, so call c_runtime_cpu_setup.
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*
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* 7. Branch to board_init_r().
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*
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* For more information see 'Board Initialisation Flow in README.
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*/
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/*
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* Macro for clearing BSS during SPL execution. Usually called during the
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* relocation process for most boards before entering board_init_r(), but
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* can also be done early before entering board_init_f() on plaforms that
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* can afford it due to sufficient memory being available early.
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*/
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.macro CLEAR_BSS
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ldr r0, =__bss_start /* this is auto-relocated! */
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#ifdef CONFIG_USE_ARCH_MEMSET
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ldr r3, =__bss_end /* this is auto-relocated! */
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mov r1, #0x00000000 /* prepare zero to clear BSS */
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subs r2, r3, r0 /* r2 = memset len */
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bl memset
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#else
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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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#endif
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.endm
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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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/* Call arch_very_early_init before initializing C runtime environment. */
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#if CONFIG_IS_ENABLED(ARCH_VERY_EARLY_INIT)
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bl arch_very_early_init
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#endif
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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_TPL_BUILD) && defined(CONFIG_TPL_NEEDS_SEPARATE_STACK)
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ldr r0, =(CONFIG_TPL_STACK)
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#elif defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK)
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ldr r0, =(CONFIG_SPL_STACK)
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#else
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ldr r0, =(CONFIG_SYS_INIT_SP_ADDR)
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#endif
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bic r0, r0, #7 /* 8-byte alignment for ABI compliance */
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mov sp, r0
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bl board_init_f_alloc_reserve
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mov sp, r0
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/* set up gd here, outside any C code */
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mov r9, r0
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bl board_init_f_init_reserve
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#if defined(CONFIG_DEBUG_UART) && CONFIG_IS_ENABLED(SERIAL)
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bl debug_uart_init
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#endif
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#if defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_EARLY_BSS)
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CLEAR_BSS
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#endif
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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 r0, [r9, #GD_START_ADDR_SP] /* sp = gd->start_addr_sp */
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bic r0, r0, #7 /* 8-byte alignment for ABI compliance */
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mov sp, r0
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ldr r9, [r9, #GD_NEW_GD] /* r9 <- gd->new_gd */
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adr lr, here
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#if defined(CONFIG_POSITION_INDEPENDENT)
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adr r0, _main
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ldr r1, _start_ofs
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add r0, r1
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ldr r1, =CONFIG_SYS_TEXT_BASE
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sub r1, r0
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add lr, r1
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#endif
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ldr r0, [r9, #GD_RELOC_OFF] /* r0 = gd->reloc_off */
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add lr, lr, r0
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#if defined(CONFIG_CPU_V7M)
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orr lr, #1 /* As required by Thumb-only */
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#endif
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ldr r0, [r9, #GD_RELOCADDR] /* r0 = gd->relocaddr */
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b relocate_code
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here:
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/*
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* now relocate vectors
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*/
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bl relocate_vectors
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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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#endif
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#if !defined(CONFIG_SPL_BUILD) || CONFIG_IS_ENABLED(FRAMEWORK)
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#if !defined(CONFIG_SPL_BUILD) || !defined(CONFIG_SPL_EARLY_BSS)
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CLEAR_BSS
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#endif
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# ifdef CONFIG_SPL_BUILD
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/* Use a DRAM stack for the rest of SPL, if requested */
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bl spl_relocate_stack_gd
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cmp r0, #0
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movne sp, r0
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movne r9, r0
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# endif
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#if ! defined(CONFIG_SPL_BUILD)
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bl coloured_LED_init
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bl red_led_on
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#endif
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/* call board_init_r(gd_t *id, ulong dest_addr) */
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mov r0, r9 /* gd_t */
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ldr r1, [r9, #GD_RELOCADDR] /* dest_addr */
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/* call board_init_r */
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#if CONFIG_IS_ENABLED(SYS_THUMB_BUILD)
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ldr lr, =board_init_r /* this is auto-relocated! */
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bx lr
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#else
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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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_start_ofs:
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.word _start - _main
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