u-boot/arch/arm/cpu/armv8/lowlevel_init.S

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ArmAsm
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/*
* A lowlevel_init function that sets up the stack to call a C function to
* perform further init.
*
* SPDX-License-Identifier: GPL-2.0+
*/
#include <asm-offsets.h>
#include <config.h>
#include <linux/linkage.h>
ENTRY(lowlevel_init)
/*
* Setup a temporary stack. Global data is not available yet.
*/
#if defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK)
ldr w0, =CONFIG_SPL_STACK
#else
ldr w0, =CONFIG_SYS_INIT_SP_ADDR
#endif
bic sp, x0, #0xf /* 16-byte alignment for ABI compliance */
/*
* Save the old LR(passed in x29) and the current LR to stack
*/
stp x29, x30, [sp, #-16]!
/*
* Call the very early init function. This should do only the
* absolute bare minimum to get started. It should not:
*
* - set up DRAM
* - use global_data
* - clear BSS
* - try to start a console
*
* For boards with SPL this should be empty since SPL can do all of
* this init in the SPL board_init_f() function which is called
* immediately after this.
*/
bl s_init
ldp x29, x30, [sp]
ret
ENDPROC(lowlevel_init)