cpu.c
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/*
* Copyright (C) 2016 Kaspar Schleiser <kaspar@schleiser.de>
* 2014, Freie Universitaet Berlin (FUB) & INRIA.
* All rights reserved.
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
#include "cpu.h"
#include "irq.h"
#include "sched.h"
#include "thread.h"
/*
* we must prevent the compiler to generate a prologue or an epilogue
* for thread_yield_higher(), since we rely on the RETI instruction at the end
* of its execution, in the inlined __restore_context() sub-function
*/
__attribute__((naked)) void thread_yield_higher(void)
{
__asm__("push r2"); /* save SR */
__disable_irq();
__save_context();
/* have sched_active_thread point to the next thread */
sched_run();
__restore_context();
UNREACHABLE();
}
/* This function calculates the ISR_usage */
int thread_arch_isr_stack_usage(void)
{
/* TODO */
return -1;
}
void *thread_arch_isr_stack_pointer(void)
{
/* TODO */
return (void *)-1;
}
void *thread_arch_isr_stack_start(void)
{
/* TODO */
return (void *)-1;
}
NORETURN void cpu_switch_context_exit(void)
{
sched_active_thread = sched_threads[0];
sched_run();
__restore_context();
UNREACHABLE();
}
/**
* mspgcc handles main specially - it does not return but falls
* through to section .fini9.
* To "fix" this, we put a return in section .fini9 to make main
* behave like a regular function. This enables a common
* thread_stack_init behavior. */
__attribute__((section (".fini9"))) void __main_epilogue(void) { __asm__("ret"); }
//----------------------------------------------------------------------------
// Processor specific routine - here for MSP
//----------------------------------------------------------------------------
char *thread_stack_init(thread_task_func_t task_func, void *arg, void *stack_start, int stack_size)
{
unsigned short stk = (unsigned short)((uintptr_t) stack_start + stack_size);
/* ensure correct stack alignment (on 16-bit boundary) */
stk &= 0xfffe;
unsigned short *stackptr = (unsigned short *)stk;
/* now make SP point on the first AVAILABLE slot in stack */
--stackptr;
*stackptr = (unsigned short) sched_task_exit;
--stackptr;
*stackptr = (unsigned short) task_func;
--stackptr;
/* initial value for SR */
*stackptr = GIE;
--stackptr;
/* set argument to task_func */
*stackptr = (unsigned short) arg;
--stackptr;
/* Space for registers. */
for (unsigned int i = 14; i > 4; i--) {
*stackptr = i;
--stackptr;
}
return (char *) stackptr;
}