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* Copyright (c) 2013-2014 Wind River Systems, Inc.
*
* SPDX-License-Identifier: Apache-2.0
*/
/**
* @file
* @brief Reset handler
*
* Reset handler that prepares the system for running C code.
*/
#include <toolchain.h>
#include <linker/sections.h>
#include <arch/cpu.h>
#include "vector_table.h"
_ASM_FILE_PROLOGUE
GTEXT(__reset)
GTEXT(memset)
GDATA(_interrupt_stack)
#if defined(CONFIG_PLATFORM_SPECIFIC_INIT)
GTEXT(z_platform_init)
#endif
/**
*
* @brief Reset vector
*
* Ran when the system comes out of reset. The processor is in thread mode with
* privileged level. At this point, the main stack pointer (MSP) is already
* pointing to a valid area in SRAM.
*
* Locking interrupts prevents anything but NMIs and hard faults from
* interrupting the CPU. A default NMI handler is already in place in the
* vector table, and the boot code should not generate hard fault, or we're in
* deep trouble.
*
* We want to use the process stack pointer (PSP) instead of the MSP, since the
* MSP is to be set up to point to the one-and-only interrupt stack during later
* boot. That would not be possible if in use for running C code.
*
* When these steps are completed, jump to _PrepC(), which will finish setting
* up the system for running C code.
*
* @return N/A
*/
SECTION_SUBSEC_FUNC(TEXT,_reset_section,__reset)
/*
* The entry point is located at the __reset symbol, which
* is fetched by a XIP image playing the role of a bootloader, which jumps to
* it, not through the reset vector mechanism. Such bootloaders might want to
* search for a __start symbol instead, so create that alias here.
*/
SECTION_SUBSEC_FUNC(TEXT,_reset_section,__start)
#if defined(CONFIG_PLATFORM_SPECIFIC_INIT)
bl z_platform_init
#endif
/* lock interrupts: will get unlocked when switch to main task */
#if defined(CONFIG_ARMV6_M_ARMV8_M_BASELINE)
cpsid i
#elif defined(CONFIG_ARMV7_M_ARMV8_M_MAINLINE)
movs.n r0, #_EXC_IRQ_DEFAULT_PRIO
msr BASEPRI, r0
#else
#error Unknown ARM architecture
#endif
#ifdef CONFIG_WDOG_INIT
/* board-specific watchdog initialization is necessary */
bl _WdogInit
#endif
#ifdef CONFIG_INIT_STACKS
ldr r0, =_interrupt_stack
ldr r1, =0xaa
ldr r2, =CONFIG_ISR_STACK_SIZE
bl memset
#endif
/*
* Set PSP and use it to boot without using MSP, so that it
* gets set to _interrupt_stack during initialization.
*/
ldr r0, =_interrupt_stack
ldr r1, =CONFIG_ISR_STACK_SIZE
adds r0, r0, r1
msr PSP, r0
mrs r0, CONTROL
movs r1, #2
orrs r0, r1 /* CONTROL_SPSEL_Msk */
msr CONTROL, r0
/*
* When changing the stack pointer, software must use an ISB instruction
* immediately after the MSR instruction. This ensures that instructions
* after the ISB instruction execute using the new stack pointer.
*/
isb
/*
* 'bl' jumps the furthest of the branch instructions that are
* supported on all platforms. So it is used when jumping to _PrepC
* (even though we do not intend to return).
*/
bl _PrepC
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