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/* Copyright 2011 The Chromium OS Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*
* Cortex-M CPU initialization
*/
#include "config.h"
.text
.syntax unified
.code 16
.global reset
.thumb_func
reset:
/*
* Ensure we're in privileged mode with main stack. Necessary if
* we've jumped directly here from another image after task_start().
*/
#ifdef CONFIG_FPU
mov r0, #(1 << 2) @ priv. mode / main stack / floating point on
#else
mov r0, #0 @ priv. mode / main stack / no floating point
#endif
msr control, r0
isb @ ensure the write is done
/* Set the vector table on our current code */
ldr r1, =vectors
ldr r2, =0xE000ED08 /* VTABLE register in SCB*/
str r1, [r2]
/* Clear BSS */
mov r0, #0
ldr r1,_bss_start
ldr r2,_bss_end
bss_loop:
cmp r1, r2
it lt
strlt r0, [r1], #4
blt bss_loop
/* Copy initialized data to Internal RAM */
ldr r0,_data_lma_start
/*
* When the .data section is linked into the .init_rom section,
* _data_lma_start is defined as a flash offset instead of a full
* 32-bit address by the linker script. Add the 32-bit flash base
* address to get a full 32-bit address.
*
* Flash locking isn't needed here as no tasks have been started.
*/
#ifdef CONFIG_CHIP_DATA_IN_INIT_ROM
ldr r1, =CONFIG_MAPPED_STORAGE_BASE
add r0, r0, r1
#endif
ldr r1,_data_start
ldr r2,_data_end
data_loop:
ldr r3, [r0], #4
cmp r1, r2
it lt
strlt r3, [r1], #4
blt data_loop
/*
* Set stack pointer. Already done by Cortex-M hardware, but re-doing
* this here allows software to jump directly to the reset vector.
*/
ldr r0, =stack_end
mov sp, r0
#ifdef CONFIG_FPU
/* Enable FPU */
/* CPACR is located at address 0xE000ED88 */
ldr r0, =0xE000ED88
/* Read CPACR */
ldr r1, [r0]
/* Set bits 20-23 to enable CP10 and CP11 coprocessors */
orr r1, r1, #(0xF << 20)
/* Write back the modified value to the CPACR */
str r1, [r0] /* wait for store to complete */
dsb
/* reset pipeline now the FPU is enabled */
isb
#endif /* CONFIG_FPU */
#ifdef CONFIG_DEBUG_DISABLE_WRITE_BUFFER
/* Disable write buffer used for default memory map accesses */
ldr r0, =0xE000E008 /* Load address of ACTLR */
ldr r1, [r0] /* Read ACTLR */
orr r1, r1, #2 /* Set DISDEFWBUF bit */
str r1, [r0] /* Write back ACTLR */
dsb /* Wait for store to complete */
isb /* Reset pipeline */
#endif /* CONFIG_DEBUG_DISABLE_WRITE_BUFFER */
/* Jump to C code */
bl main
/* That should not return. If it does, loop forever. */
fini_loop:
b fini_loop
.align 2
_bss_start:
.long __bss_start
_bss_end:
.long __bss_end
_data_start:
.long __data_start
_data_end:
.long __data_end
_data_lma_start:
.long __data_lma_start
/* Reserve space for system stack */
.section .bss.system_stack
stack_start:
.space CONFIG_STACK_SIZE, 0
stack_end:
.global stack_end
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