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/*
* Copyright (c) 2013-2014 Wind River Systems, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* @file
* @brief ARM CORTEX-M exception/interrupt exit API
*
*
* Provides functions for performing kernel handling when exiting exceptions or
* interrupts that are installed directly in the vector table (i.e. that are not
* wrapped around by _isr_wrapper()).
*/
#define _ASMLANGUAGE
#include <kernel_structs.h>
#include <offsets_short.h>
#include <toolchain.h>
#include <arch/cpu.h>
_ASM_FILE_PROLOGUE
GTEXT(_ExcExit)
GTEXT(_IntExit)
GDATA(_kernel)
/**
*
* @brief Kernel housekeeping when exiting interrupt handler installed
* directly in vector table
*
* Kernel allows installing interrupt handlers (ISRs) directly into the vector
* table to get the lowest interrupt latency possible. This allows the ISR to be
* invoked directly without going through a software interrupt table. However,
* upon exiting the ISR, some kernel work must still be performed, namely
* possible context switching. While ISRs connected in the software interrupt
* table do this automatically via a wrapper, ISRs connected directly in the
* vector table must invoke _IntExit() as the *very last* action before
* returning.
*
* e.g.
*
* void myISR(void)
* {
* printk("in %s\n", __FUNCTION__);
* doStuff();
* _IntExit();
* }
*
* @return N/A
*/
SECTION_SUBSEC_FUNC(TEXT, _HandlerModeExit, _IntExit)
/* _IntExit falls through to _ExcExit (they are aliases of each other) */
/**
*
* @brief Kernel housekeeping when exiting exception handler installed
* directly in vector table
*
* See _IntExit().
*
* @return N/A
*/
SECTION_SUBSEC_FUNC(TEXT, _HandlerModeExit, _ExcExit)
#ifdef CONFIG_PREEMPT_ENABLED
ldr r0, =_kernel
ldr r1, [r0, #_kernel_offset_to_current]
/*
* Non-preemptible thread ? Do not schedule (see explanation of
* preempt field in kernel_struct.h).
*/
ldrh r2, [r1, #_thread_offset_to_preempt]
cmp r2, #_PREEMPT_THRESHOLD
bhi _EXIT_EXC
ldr r0, [r0, _kernel_offset_to_ready_q_cache]
cmp r0, r1
beq _EXIT_EXC
/* context switch required, pend the PendSV exception */
ldr r1, =_SCS_ICSR
ldr r2, =_SCS_ICSR_PENDSV
str r2, [r1]
_ExcExitWithGdbStub:
_EXIT_EXC:
#endif /* CONFIG_PREEMPT_ENABLED */
bx lr
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