2 * Copyright © 2009 Keith Packard <keithp@keithp.com>
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; version 2 of the License.
8 * This program is distributed in the hope that it will be useful, but
9 * WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
11 * General Public License for more details.
13 * You should have received a copy of the GNU General Public License along
14 * with this program; if not, write to the Free Software Foundation, Inc.,
15 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
20 #define AO_NO_TASK_INDEX 0xff
22 __xdata struct ao_task * __xdata ao_tasks[AO_NUM_TASKS];
23 __data uint8_t ao_num_tasks;
24 __data uint8_t ao_cur_task_index;
25 __xdata struct ao_task *__data ao_cur_task;
29 #define PUSH8(stack, val) (*((stack)--) = (val))
32 ao_init_stack(__xdata struct ao_task *task, void (*start)(void))
34 uint8_t *sp = task->stack + AO_STACK_SIZE - 1;
35 uint16_t a = (uint16_t) start;
42 /* Clear register values */
47 /* SREG with interrupts enabled */
53 ao_init_stack(__xdata struct ao_task *task, void (*start)(void))
55 uint8_t __xdata *stack = task->stack;
57 * Construct a stack frame so that it will 'return'
58 * to the start of the task
61 *stack++ = ((uint16_t) start);
62 *stack++ = ((uint16_t) start) >> 8;
64 /* and the stuff saved by ao_switch */
65 *stack++ = 0; /* acc */
66 *stack++ = 0x80; /* IE */
67 *stack++ = 0; /* DPL */
68 *stack++ = 0; /* DPH */
70 *stack++ = 0; /* R2 */
71 *stack++ = 0; /* R3 */
72 *stack++ = 0; /* R4 */
73 *stack++ = 0; /* R5 */
74 *stack++ = 0; /* R6 */
75 *stack++ = 0; /* R7 */
76 *stack++ = 0; /* R0 */
77 *stack++ = 0; /* R1 */
78 *stack++ = 0; /* PSW */
79 *stack++ = 0; /* BP */
80 task->stack_count = stack - task->stack;
85 ao_add_task(__xdata struct ao_task * task, void (*start)(void), __code char *name) __reentrant
89 if (ao_num_tasks == AO_NUM_TASKS)
90 ao_panic(AO_PANIC_NO_TASK);
91 for (task_id = 1; task_id != 0; task_id++) {
92 for (t = 0; t < ao_num_tasks; t++)
93 if (ao_tasks[t]->task_id == task_id)
95 if (t == ao_num_tasks)
98 ao_tasks[ao_num_tasks++] = task;
99 task->task_id = task_id;
102 ao_init_stack(task, start);
106 ao_show_task_from(void)
109 printf("switching from %s\n", ao_cur_task->name);
113 ao_show_task_to(void)
115 printf("switching to %s\n", ao_cur_task->name);
118 /* Task switching function. This must not use any stack variables */
120 ao_yield(void) __naked
123 asm("push r31" "\n\t" "push r30");
124 asm("push r29" "\n\t" "push r28" "\n\t" "push r27" "\n\t" "push r26" "\n\t" "push r25");
125 asm("push r24" "\n\t" "push r23" "\n\t" "push r22" "\n\t" "push r21" "\n\t" "push r20");
126 asm("push r19" "\n\t" "push r18" "\n\t" "push r17" "\n\t" "push r16" "\n\t" "push r15");
127 asm("push r14" "\n\t" "push r13" "\n\t" "push r12" "\n\t" "push r11" "\n\t" "push r10");
128 asm("push r9" "\n\t" "push r8" "\n\t" "push r7" "\n\t" "push r6" "\n\t" "push r5");
129 asm("push r4" "\n\t" "push r3" "\n\t" "push r2" "\n\t" "push r1" "\n\t" "push r0");
131 asm("in r0, __SREG__" "\n\t" "push r0");
134 /* Save current context */
136 /* Push ACC first, as when restoring the context it must be restored
137 * last (it is used to set the IE register). */
139 /* Store the IE register then enable interrupts. */
161 if (ao_cur_task_index == AO_NO_TASK_INDEX)
162 ao_cur_task_index = ao_num_tasks-1;
167 asm("in %0,__SP_L__" : "=&r" (sp_l) );
168 asm("in %0,__SP_H__" : "=&r" (sp_h) );
169 ao_cur_task->sp = (uint8_t *) ((uint16_t) sp_l | ((uint16_t) sp_h << 8));
172 __data uint8_t *stack_ptr;
173 __xdata uint8_t *save_ptr;
174 /* Save the current stack */
175 stack_len = SP - (AO_STACK_START - 1);
176 ao_cur_task->stack_count = stack_len;
177 stack_ptr = (uint8_t __data *) AO_STACK_START;
178 save_ptr = (uint8_t __xdata *) ao_cur_task->stack;
180 *save_ptr++ = *stack_ptr++;
186 /* Empty the stack; might as well let interrupts have the whole thing */
187 SP = AO_STACK_START - 1;
191 /* Find a task to run. If there isn't any runnable task,
192 * this loop will run forever, which is just fine
195 __pdata uint8_t ao_next_task_index = ao_cur_task_index;
197 ++ao_next_task_index;
198 if (ao_next_task_index == ao_num_tasks)
199 ao_next_task_index = 0;
201 ao_cur_task = ao_tasks[ao_next_task_index];
202 if (ao_cur_task->wchan == NULL) {
203 ao_cur_task_index = ao_next_task_index;
207 /* Check if the alarm is set for a time which has passed */
208 if (ao_cur_task->alarm &&
209 (int16_t) (ao_time() - ao_cur_task->alarm) >= 0) {
210 ao_cur_task_index = ao_next_task_index;
216 /* Enter lower power mode when there isn't anything to do */
217 if (ao_next_task_index == ao_cur_task_index)
226 sp_l = (uint16_t) ao_cur_task->sp;
227 sp_h = ((uint16_t) ao_cur_task->sp) >> 8;
230 asm("out __SP_H__,%0" : : "r" (sp_h) );
231 asm("out __SP_L__,%0" : : "r" (sp_l) );
234 asm("pop r0" "\n\t" "pop r1" "\n\t" "pop r2" "\n\t" "pop r3" "\n\t" "pop r4");
235 asm("pop r5" "\n\t" "pop r6" "\n\t" "pop r7" "\n\t" "pop r8" "\n\t" "pop r9");
236 asm("pop r10" "\n\t" "pop r11" "\n\t" "pop r12" "\n\t" "pop r13" "\n\t" "pop r14");
237 asm("pop r15" "\n\t" "pop r16" "\n\t" "pop r17" "\n\t" "pop r18" "\n\t" "pop r19");
238 asm("pop r20" "\n\t" "pop r21" "\n\t" "pop r22" "\n\t" "pop r23" "\n\t" "pop r24");
239 asm("pop r25" "\n\t" "pop r26" "\n\t" "pop r27" "\n\t" "pop r28" "\n\t" "pop r29");
240 asm("pop r30" "\n\t" "pop r31");
246 __data uint8_t *stack_ptr;
247 __xdata uint8_t *save_ptr;
249 /* Restore the old stack */
250 stack_len = ao_cur_task->stack_count;
251 SP = AO_STACK_START - 1 + stack_len;
253 stack_ptr = (uint8_t __data *) AO_STACK_START;
254 save_ptr = (uint8_t __xdata *) ao_cur_task->stack;
256 *stack_ptr++ = *save_ptr++;
274 /* The next byte of the stack is the IE register. Only the global
275 enable bit forms part of the task context. Pop off the IE then set
276 the global enable bit to match that of the stored IE register. */
284 /* Finally pop off the ACC, which was the first register saved. */
292 ao_sleep(__xdata void *wchan)
295 ao_cur_task->wchan = wchan;
298 ao_cur_task->alarm = 0;
299 if (ao_cur_task->wchan) {
300 ao_cur_task->wchan = NULL;
307 ao_wakeup(__xdata void *wchan)
311 for (i = 0; i < ao_num_tasks; i++)
312 if (ao_tasks[i]->wchan == wchan)
313 ao_tasks[i]->wchan = NULL;
317 ao_alarm(uint16_t delay)
319 /* Make sure we sleep *at least* delay ticks, which means adding
320 * one to account for the fact that we may be close to the next tick
322 if (!(ao_cur_task->alarm = ao_time() + delay + 1))
323 ao_cur_task->alarm = 1;
327 ao_exit(void) __critical
331 for (i = ao_cur_task_index; i < ao_num_tasks; i++)
332 ao_tasks[i] = ao_tasks[i+1];
333 ao_cur_task_index = AO_NO_TASK_INDEX;
335 /* we'll never get back here */
342 __xdata struct ao_task *task;
344 for (i = 0; i < ao_num_tasks; i++) {
346 printf("%12s: wchan %04x\n",
348 (int16_t) task->wchan);
353 ao_start_scheduler(void)
355 ao_cur_task_index = AO_NO_TASK_INDEX;