/* $Id$ */ /* * Copyright (c) 2010 Dimitri Sokolyuk * * Permission to use, copy, modify, and distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ /* * based on TinyRealTime by Dan Henriksson and Anton Cervin * http://www.control.lth.se/Publication/hen+04t.html */ #include #include #include #include #include "kernel.h" #include "stack.h" #include "queue.h" #define DEBUG 0 enum State { TERMINATED, RUNQ, TIMEQ, WAITQ, SIGNAL }; #define LO8(x) ((uint8_t)((uint16_t)(x))) #define HI8(x) ((uint8_t)((uint16_t)(x) >> 8)) #define SCHEDULE TIMER1_COMPA_vect #define DISTANCE(from, to) ((int32_t)((to) - (from))) #define EPOCH (INT32_MAX >> 1) #define NOW(hi, lo) (((uint32_t)(hi) << 0x10) | (lo)) struct task { uint32_t release; uint16_t sp; /* stack pointer */ uint8_t state; uint8_t prio; uint8_t sema; TAILQ_ENTRY(task) link; }; struct kernel { TAILQ_HEAD(queue, task) runq[PRIORITIES], timeq, waitq[SEMAPHORES]; struct task task[1 + TASKS]; struct task *nextfree; struct task *current; uint16_t cycles; uint8_t *freemem; uint8_t semaphore[SEMAPHORES]; } kernel; ISR(TIMER1_OVF_vect) { ++kernel.cycles; } ISR(TIMER1_COMPA_vect, ISR_NAKED) { struct task *tp, *tmp; int32_t dist; uint32_t now; uint16_t nexthit; uint8_t prio; PUSH_ALL(); now = NOW(kernel.cycles, TCNT1); #if DEBUG PORTB ^= _BV(PB1); /* DEBUG */ #endif kernel.current->sp = SP; TAILQ_REMOVE(&kernel.runq[kernel.current->prio], kernel.current, link); nexthit = 0xffff; /* release waiting tasks */ TAILQ_FOREACH_SAFE(tp, &kernel.timeq, link, tmp) { dist = DISTANCE(now, tp->release); if (dist <= 0) { tp->state = RUNQ; TAILQ_REMOVE(&kernel.timeq, tp, link); TAILQ_INSERT_TAIL(&kernel.runq[tp->prio], tp, link); } else if (dist < nexthit) nexthit = dist; else break; } again: switch (kernel.current->state) { case RUNQ: TAILQ_INSERT_TAIL(&kernel.runq[kernel.current->prio], kernel.current, link); break; case TIMEQ: TAILQ_FOREACH(tp, &kernel.timeq, link) if (DISTANCE(kernel.current->release, tp->release) > 0) break; if (tp) TAILQ_INSERT_BEFORE(tp, kernel.current, link); else TAILQ_INSERT_TAIL(&kernel.timeq, kernel.current, link); break; case WAITQ: if (kernel.semaphore[kernel.current->sema] == 0) { /* occupy semaphore */ kernel.semaphore[kernel.current->sema] = 1; kernel.current->state = RUNQ; goto again; /* put current task back on runq */ } else TAILQ_INSERT_TAIL(&kernel.waitq[kernel.current->sema], kernel.current, link); break; case SIGNAL: tp = TAILQ_FIRST(&kernel.waitq[kernel.current->sema]); if (tp) { tp->state = RUNQ; TAILQ_REMOVE(&kernel.waitq[kernel.current->sema], tp, link); TAILQ_INSERT_TAIL(&kernel.runq[tp->prio], tp, link); /* occupy semaphore */ kernel.semaphore[kernel.current->sema] = 1; } else kernel.semaphore[kernel.current->sema] = 0; kernel.current->state = RUNQ; goto again; /* put current task back on runq */ default: break; } for (prio = 0; prio < PRIORITIES - 1; prio++) if (!TAILQ_EMPTY(&kernel.runq[prio])) break; if (TAILQ_EMPTY(&kernel.runq[prio])) TAILQ_INSERT_TAIL(&kernel.runq[prio], &kernel.task[0], link); kernel.current = TAILQ_FIRST(&kernel.runq[prio]); SP = kernel.current->sp; OCR1A = (uint16_t)(now + nexthit); POP_ALL(); reti(); } void init(uint8_t stack) { uint8_t i; cli(); /* Set up timer 1 */ TCNT1 = 0; /* reset timer */ TCCR1A = 0; /* normal operation */ TCCR1B = TIMER_FLAGS; /* prescale */ TIMSK = (_BV(OCIE1A) | _BV(TOIE1)); /* enable interrupts */ OCR1A = 0; /* default overflow */ #if DEBUG DDRB |= _BV(PB1); /* DEBUG */ #endif memset(&kernel, 0, sizeof(kernel)); for (i = 0; i < PRIORITIES; i++) TAILQ_INIT(&kernel.runq[i]); TAILQ_INIT(&kernel.timeq); for (i = 0; i < SEMAPHORES; i++) TAILQ_INIT(&kernel.waitq[i]); kernel.nextfree = &kernel.task[1]; kernel.freemem = (void *)(RAMEND - stack); kernel.current = &kernel.task[0]; kernel.current->state = TERMINATED; kernel.current->prio = PRIORITIES - 1; kernel.current->release = 0; TAILQ_INSERT_TAIL(&kernel.runq[PRIORITIES - 1], &kernel.task[0], link); sei(); } void exec(void (*fun)(void *), void *args, uint8_t stack, uint8_t prio) { struct task *t; uint8_t *sp; cli(); sp = kernel.freemem; kernel.freemem -= stack; /* initialize stack */ *sp-- = LO8(fun); /* PC(lo) */ *sp-- = HI8(fun); /* PC(hi) */ sp -= 25; memset(sp, 0, 25); /* r1, r0, SREG, r2-r23 */ *sp-- = LO8(args); /* r24 */ *sp-- = HI8(args); /* r25 */ sp -= 6; memset(sp, 0, 6); /* r26-r31 */ t = kernel.nextfree++; t->release = NOW(kernel.cycles, TCNT1); t->prio = prio; t->sema = 0; t->sp = (uint16_t)sp; /* SP */ t->state = TIMEQ; TAILQ_INSERT_TAIL(&kernel.timeq, t, link); SCHEDULE(); } void wait(uint8_t sema) { cli(); kernel.current->sema = sema; kernel.current->state = WAITQ; SCHEDULE(); } void signal(uint8_t sema) { cli(); kernel.current->state = SIGNAL; SCHEDULE(); } void sleep(uint32_t ticks) { cli(); kernel.current->release += ticks; kernel.current->state = TIMEQ; SCHEDULE(); } uint32_t now(void) { return NOW(kernel.cycles, TCNT1); } void suspend(void) { cli(); kernel.current->state = TERMINATED; SCHEDULE(); } uint8_t running(void) { return kernel.current - kernel.task; }