/* $Id$ */ /* * 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 #include "kernel.h" #include "stack.h" #include "queue.h" 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 */ TAILQ_ENTRY(task) r_link, t_link, w_link; }; struct kernel { TAILQ_HEAD(queue, task) runq, timeq, waitq[SEMAPHORES]; struct task idle[1 + TASKS]; struct task *last; struct task *current; uint16_t cycles; uint8_t *freemem; uint8_t semaphore; } kernel; ISR(TIMER1_OVF_vect) { ++kernel.cycles; } ISR(TIMER1_COMPA_vect, ISR_NAKED) { struct task *tp, *tmp; uint32_t now; uint16_t nexthit; int32_t dist; PUSH_ALL(); now = NOW(kernel.cycles, TCNT1); /* release waiting tasks */ TAILQ_FOREACH_SAFE(tp, &kernel.timeq, t_link, tmp) { if (DISTANCE(tp->release, now) >= 0) { TAILQ_REMOVE(&kernel.timeq, tp, t_link); TAILQ_INSERT_TAIL(&kernel.runq, tp, r_link); } else break; } /* drop idle */ if (kernel.current == kernel.idle) TAILQ_REMOVE(&kernel.runq, kernel.current, r_link); /* runq not changed && not empty -> yield */ if (kernel.current == TAILQ_FIRST(&kernel.runq)) { TAILQ_REMOVE(&kernel.runq, kernel.current, r_link); TAILQ_INSERT_TAIL(&kernel.runq, kernel.current, r_link); } /* go idle if nothing to do */ if (TAILQ_EMPTY(&kernel.runq)) TAILQ_INSERT_TAIL(&kernel.runq, kernel.idle, r_link); nexthit = INT16_MAX; /* max time slice */ if ((tp = TAILQ_FIRST(&kernel.timeq))) { dist = DISTANCE(now, tp->release); if (dist < nexthit) nexthit = dist; } OCR1A = (uint16_t)(now + nexthit); /* switch context */ kernel.current->sp = SP; kernel.current = TAILQ_FIRST(&kernel.runq); SP = kernel.current->sp; 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 */ TAILQ_INIT(&kernel.runq); TAILQ_INIT(&kernel.timeq); for (i = 0; i < SEMAPHORES; i++) TAILQ_INIT(&kernel.waitq[i]); kernel.idle->release = 0; kernel.idle->sp = SP; /* XXX not needed at all */ TAILQ_INSERT_TAIL(&kernel.runq, kernel.idle, r_link); kernel.current = TAILQ_FIRST(&kernel.runq); kernel.last = kernel.idle; kernel.cycles = 0; kernel.freemem = (uint8_t *)(RAMEND - stack); kernel.semaphore = 0; sei(); } void exec(void (*fun)(void *), void *args, uint8_t stack) { struct task *tp; uint8_t *sp; cli(); sp = kernel.freemem; kernel.freemem -= stack + 2; /* +PC */ /* 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 */ tp = ++kernel.last; tp->release = 0; tp->sp = (uint16_t)sp; /* SP */ TAILQ_INSERT_TAIL(&kernel.runq, tp, r_link); SCHEDULE(); } void wait(uint8_t chan) { cli(); if (kernel.semaphore & _BV(chan)) { /* semaphore busy, go into wait queue */ TAILQ_REMOVE(&kernel.runq, kernel.current, r_link); TAILQ_INSERT_TAIL(&kernel.waitq[chan], kernel.current, w_link); SCHEDULE(); } else { /* occupy semaphore and continue */ kernel.semaphore |= _BV(chan); sei(); } } void signal(uint8_t chan) { struct task *tp; cli(); if ((tp = TAILQ_FIRST(&kernel.waitq[chan]))) { /* release first waiting task from wait queue */ TAILQ_REMOVE(&kernel.waitq[chan], tp, w_link); TAILQ_INSERT_TAIL(&kernel.runq, tp, r_link); SCHEDULE(); } else { /* clear semaphore and continue */ kernel.semaphore &= ~_BV(chan); sei(); } } void sleep(uint32_t sec, uint32_t usec) { struct task *tp; cli(); TAILQ_REMOVE(&kernel.runq, kernel.current, r_link); kernel.current->release += SEC(sec) + USEC(usec); /* find right position on time queue */ TAILQ_FOREACH(tp, &kernel.timeq, t_link) if (DISTANCE(kernel.current->release, tp->release) > 0) break; if (tp) TAILQ_INSERT_BEFORE(tp, kernel.current, t_link); else TAILQ_INSERT_TAIL(&kernel.timeq, kernel.current, t_link); SCHEDULE(); } void yield(void) { cli(); SCHEDULE(); } void suspend(void) { cli(); TAILQ_REMOVE(&kernel.runq, kernel.current, r_link); SCHEDULE(); } uint32_t now(void) { return NOW(kernel.cycles, TCNT1); } uint8_t running(void) { return kernel.current - kernel.idle; } void reboot(void) { wdt_enable(WDTO_15MS); }