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/*
* crt0 - C-runtime startup Code for AArch64 U-Boot
*
* (C) Copyright 2013
* David Feng <fenghua@phytium.com.cn>
*
* (C) Copyright 2012
* Albert ARIBAUD <albert.u.boot@aribaud.net>
*
* SPDX-License-Identifier: GPL-2.0+
*/
#include <config.h>
#include <asm-offsets.h>
#include <asm/macro.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. GD should be zeroed
* before board_init_f() is called.
*
* 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.
*
* 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.
*
* 4a.For U-Boot proper (not SPL), call relocate_code(). This function
* relocates U-Boot from its current location into the relocation
* destination computed by board_init_f().
*
* 4b.For SPL, board_init_f() just returns (to crt0). There is no
* code relocation in SPL.
*
* 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 (for SPL moving the stack and GD into RAM is optional - see
* CONFIG_SPL_STACK_R). GD has retained values set by board_init_f().
*
* TODO: For SPL, implement stack relocation on AArch64.
*
* 6. For U-Boot proper (not SPL), some CPUs have some work left to do
* at this point regarding memory, so call c_runtime_cpu_setup.
*
* 7. Branch to board_init_r().
*
* For more information see 'Board Initialisation Flow in README.
*/
ENTRY(_main)
/*
* Set up initial C runtime environment and call board_init_f(0).
*/
#if defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK)
ldr x0, =(CONFIG_SPL_STACK)
#else
ldr x0, =(CONFIG_SYS_INIT_SP_ADDR)
#endif
bic sp, x0, #0xf /* 16-byte alignment for ABI compliance */
mov x0, sp
bl board_init_f_alloc_reserve
mov sp, x0
/* set up gd here, outside any C code */
mov x18, x0
bl board_init_f_init_reserve
mov x0, #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 x0, [x18, #GD_START_ADDR_SP] /* x0 <- gd->start_addr_sp */
bic sp, x0, #0xf /* 16-byte alignment for ABI compliance */
ldr x18, [x18, #GD_BD] /* x18 <- gd->bd */
sub x18, x18, #GD_SIZE /* new GD is below bd */
adr lr, relocation_return
ldr x9, [x18, #GD_RELOC_OFF] /* x9 <- gd->reloc_off */
add lr, lr, x9 /* new return address after relocation */
ldr x0, [x18, #GD_RELOCADDR] /* x0 <- gd->relocaddr */
b relocate_code
relocation_return:
/*
* Set up final (full) environment
*/
bl c_runtime_cpu_setup /* still call old routine */
/* TODO: For SPL, call spl_relocate_stack_gd() to alloc stack relocation */
/*
* Clear BSS section
*/
ldr x0, =__bss_start /* this is auto-relocated! */
ldr x1, =__bss_end /* this is auto-relocated! */
mov x2, #0
clear_loop:
str x2, [x0]
add x0, x0, #8
cmp x0, x1
b.lo clear_loop
/* call board_init_r(gd_t *id, ulong dest_addr) */
mov x0, x18 /* gd_t */
ldr x1, [x18, #GD_RELOCADDR] /* dest_addr */
b board_init_r /* PC relative jump */
/* NOTREACHED - board_init_r() does not return */
#endif /* !CONFIG_SPL_BUILD */
ENDPROC(_main)
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