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/*
ChibiOS/RT - Copyright (C) 2006,2007,2008,2009,2010,
2011 Giovanni Di Sirio.
This file is part of ChibiOS/RT.
ChibiOS/RT is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
ChibiOS/RT is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/**
* @file GCC/ARMCMx/chcore_v6m.c
* @brief ARMv6-M architecture port code.
*
* @addtogroup ARMCMx_V6M_CORE
* @{
*/
#include "ch.h"
/**
* @brief System Timer vector.
* @details This interrupt is used as system tick.
* @note The timer must be initialized in the startup code.
*/
CH_IRQ_HANDLER(SysTickVector) {
CH_IRQ_PROLOGUE();
chSysLockFromIsr();
chSysTimerHandlerI();
chSysUnlockFromIsr();
CH_IRQ_EPILOGUE();
}
#if !CORTEX_ALTERNATE_SWITCH || defined(__DOXYGEN__)
/**
* @brief NMI vector.
* @details The NMI vector is used for exception mode re-entering after a
* context switch.
*/
void NMIVector(void) {
register struct extctx *ctxp;
/* Discarding the current exception context and positioning the stack to
point to the real one.*/
asm volatile ("mrs %0, PSP" : "=r" (ctxp) : : "memory");
ctxp++;
asm volatile ("msr PSP, %0" : : "r" (ctxp) : "memory");
port_unlock_from_isr();
}
#endif /* !CORTEX_ALTERNATE_SWITCH */
#if CORTEX_ALTERNATE_SWITCH || defined(__DOXYGEN__)
/**
* @brief PendSV vector.
* @details The PendSV vector is used for exception mode re-entering after a
* context switch.
*/
void PendSVVector(void) {
register struct extctx *ctxp;
/* Discarding the current exception context and positioning the stack to
point to the real one.*/
asm volatile ("mrs %0, PSP" : "=r" (ctxp) : : "memory");
ctxp++;
asm volatile ("msr PSP, %0" : : "r" (ctxp) : "memory");
}
#endif /* CORTEX_ALTERNATE_SWITCH */
/**
* @brief Post-IRQ switch code.
* @details The switch is performed in thread context then an NMI exception
* is enforced in order to return to the exact point before the
* preemption.
*/
#if !defined(__DOXYGEN__)
__attribute__((naked))
#endif
void _port_switch_from_isr(void) {
if (chSchIsPreemptionRequired())
chSchDoReschedule();
#if CORTEX_ALTERNATE_SWITCH
SCB_ICSR = ICSR_PENDSVSET;
port_unlock();
#else
SCB_ICSR = ICSR_NMIPENDSET;
#endif
/* The following loop should never be executed, the exception will kick in
immediately.*/
while (TRUE)
;
}
#define PUSH_CONTEXT(sp) { \
asm volatile ("push {r4, r5, r6, r7, lr} \n\t" \
"mov r4, r8 \n\t" \
"mov r5, r9 \n\t" \
"mov r6, r10 \n\t" \
"mov r7, r11 \n\t" \
"push {r4, r5, r6, r7}" : : : "memory"); \
}
#define POP_CONTEXT(sp) { \
asm volatile ("pop {r4, r5, r6, r7} \n\t" \
"mov r8, r4 \n\t" \
"mov r9, r5 \n\t" \
"mov r10, r6 \n\t" \
"mov r11, r7 \n\t" \
"pop {r4, r5, r6, r7, pc}" : : "r" (sp) : "memory"); \
}
/**
* @brief Performs a context switch between two threads.
* @details This is the most critical code in any port, this function
* is responsible for the context switch between 2 threads.
* @note The implementation of this code affects <b>directly</b> the context
* switch performance so optimize here as much as you can.
*
* @param[in] ntp the thread to be switched in
* @param[in] otp the thread to be switched out
*/
#if !defined(__DOXYGEN__)
__attribute__((naked))
#endif
void _port_switch(Thread *ntp, Thread *otp) {
register struct intctx *r13 asm ("r13");
PUSH_CONTEXT(r13);
otp->p_ctx.r13 = r13;
r13 = ntp->p_ctx.r13;
POP_CONTEXT(r13);
}
/**
* @brief IRQ epilogue code.
*
* @param[in] lr value of the @p LR register on ISR entry
*/
void _port_irq_epilogue(regarm_t lr) {
if (lr != (regarm_t)0xFFFFFFF1) {
register struct extctx *ctxp;
port_lock_from_isr();
/* Adding an artificial exception return context, there is no need to
populate it fully.*/
asm volatile ("mrs %0, PSP" : "=r" (ctxp) : : "memory");
ctxp--;
asm volatile ("msr PSP, %0" : : "r" (ctxp) : "memory");
ctxp->pc = _port_switch_from_isr;
ctxp->xpsr = (regarm_t)0x01000000;
/* Note, returning without unlocking is intentional, this is done in
order to keep the rest of the context switching atomic.*/
}
}
/**
* @brief Start a thread by invoking its work function.
* @details If the work function returns @p chThdExit() is automatically
* invoked.
*/
void _port_thread_start(void) {
chSysUnlock();
asm volatile ("mov r0, r5 \n\t"
"blx r4 \n\t"
"bl chThdExit");
}
/** @} */
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