circuitpython/ports/stm32/pendsv.c

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/*
* This file is part of the MicroPython project, http://micropython.org/
*
* The MIT License (MIT)
*
* Copyright (c) 2013, 2014 Damien P. George
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include <stdlib.h>
#include "py/runtime.h"
#include "lib/utils/interrupt_char.h"
#include "pendsv.h"
#include "irq.h"
// This variable is used to save the exception object between a ctrl-C and the
// PENDSV call that actually raises the exception. It must be non-static
// otherwise gcc-5 optimises it away. It can point to the heap but is not
// traced by GC. This is okay because we only ever set it to
// mp_kbd_exception which is in the root-pointer set.
void *pendsv_object;
#if defined(PENDSV_DISPATCH_NUM_SLOTS)
uint32_t pendsv_dispatch_active;
pendsv_dispatch_t pendsv_dispatch_table[PENDSV_DISPATCH_NUM_SLOTS];
#endif
void pendsv_init(void) {
#if defined(PENDSV_DISPATCH_NUM_SLOTS)
pendsv_dispatch_active = false;
#endif
// set PendSV interrupt at lowest priority
NVIC_SetPriority(PendSV_IRQn, IRQ_PRI_PENDSV);
}
// Call this function to raise a pending exception during an interrupt.
// It will first try to raise the exception "softly" by setting the
// mp_pending_exception variable and hoping that the VM will notice it.
// If this function is called a second time (ie with the mp_pending_exception
// variable already set) then it will force the exception by using the hardware
// PENDSV feature. This will wait until all interrupts are finished then raise
// the given exception object using nlr_jump in the context of the top-level
// thread.
void pendsv_kbd_intr(void) {
if (MP_STATE_VM(mp_pending_exception) == MP_OBJ_NULL) {
mp_keyboard_interrupt();
} else {
MP_STATE_VM(mp_pending_exception) = MP_OBJ_NULL;
pendsv_object = &MP_STATE_VM(mp_kbd_exception);
SCB->ICSR = SCB_ICSR_PENDSVSET_Msk;
}
}
#if defined(PENDSV_DISPATCH_NUM_SLOTS)
void pendsv_schedule_dispatch(size_t slot, pendsv_dispatch_t f) {
pendsv_dispatch_table[slot] = f;
pendsv_dispatch_active = true;
SCB->ICSR = SCB_ICSR_PENDSVSET_Msk;
}
void pendsv_dispatch_handler(void) {
for (size_t i = 0; i < PENDSV_DISPATCH_NUM_SLOTS; ++i) {
if (pendsv_dispatch_table[i] != NULL) {
pendsv_dispatch_table[i] = NULL;
pendsv_dispatch_table[i]();
}
}
}
#endif
__attribute__((naked)) void PendSV_Handler(void) {
// Handle a PendSV interrupt
//
// For the case of an asynchronous exception, re-jig the
// stack so that when we return from this interrupt handler
// it returns instead to nlr_jump with argument pendsv_object
// note that stack has a different layout if DEBUG is enabled
//
// For the case of a thread switch, swap stacks.
//
// on entry to this (naked) function, stack has the following layout:
//
// stack layout with DEBUG disabled:
// sp[6]: pc=r15
// sp[5]: lr=r14
// sp[4]: r12
// sp[3]: r3
// sp[2]: r2
// sp[1]: r1
// sp[0]: r0
//
// stack layout with DEBUG enabled:
// sp[8]: pc=r15
// sp[7]: lr=r14
// sp[6]: r12
// sp[5]: r3
// sp[4]: r2
// sp[3]: r1
// sp[2]: r0
// sp[1]: 0xfffffff9
// sp[0]: ?
__asm volatile (
#if defined(PENDSV_DISPATCH_NUM_SLOTS)
// Check if there are any pending calls to dispatch to
"ldr r1, pendsv_dispatch_active_ptr\n"
"ldr r0, [r1]\n"
"cmp r0, 0\n"
"beq .no_dispatch\n"
"mov r2, #0\n"
"str r2, [r1]\n" // clear pendsv_dispatch_active
"b pendsv_dispatch_handler\n" // jump to the handler
".no_dispatch:\n"
#endif
// Check if there is an active object to throw via nlr_jump
"ldr r1, pendsv_object_ptr\n"
"ldr r0, [r1]\n"
"cmp r0, 0\n"
"beq .no_obj\n"
#if defined(PENDSV_DEBUG)
"str r0, [sp, #8]\n" // store to r0 on stack
#else
"str r0, [sp, #0]\n" // store to r0 on stack
#endif
"mov r0, #0\n"
"str r0, [r1]\n" // clear pendsv_object
"ldr r0, nlr_jump_ptr\n"
#if defined(PENDSV_DEBUG)
"str r0, [sp, #32]\n" // store to pc on stack
#else
"str r0, [sp, #24]\n" // store to pc on stack
#endif
"bx lr\n" // return from interrupt; will return to nlr_jump
".no_obj:\n" // pendsv_object==NULL
#if MICROPY_PY_THREAD
// Do a thread context switch
"push {r4-r11, lr}\n"
"vpush {s16-s31}\n"
"mrs r5, primask\n" // save PRIMASK in r5
"cpsid i\n" // disable interrupts while we change stacks
"mov r0, sp\n" // pass sp to save
"mov r4, lr\n" // save lr because we are making a call
"bl pyb_thread_next\n" // get next thread to execute
"mov lr, r4\n" // restore lr
"mov sp, r0\n" // switch stacks
"msr primask, r5\n" // reenable interrupts
"vpop {s16-s31}\n"
"pop {r4-r11, lr}\n"
"bx lr\n" // return from interrupt; will return to new thread
#else
// Spurious pendsv, just return
"bx lr\n"
#endif
// Data
".align 2\n"
#if defined(PENDSV_DISPATCH_NUM_SLOTS)
"pendsv_dispatch_active_ptr: .word pendsv_dispatch_active\n"
#endif
"pendsv_object_ptr: .word pendsv_object\n"
"nlr_jump_ptr: .word nlr_jump\n"
);
}