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);
105 /* Task switching function. This must not use any stack variables */
107 ao_yield(void) __naked
110 asm("push r31" "\n\t" "push r30");
111 asm("push r29" "\n\t" "push r28" "\n\t" "push r27" "\n\t" "push r26" "\n\t" "push r25");
112 asm("push r24" "\n\t" "push r23" "\n\t" "push r22" "\n\t" "push r21" "\n\t" "push r20");
113 asm("push r19" "\n\t" "push r18" "\n\t" "push r17" "\n\t" "push r16" "\n\t" "push r15");
114 asm("push r14" "\n\t" "push r13" "\n\t" "push r12" "\n\t" "push r11" "\n\t" "push r10");
115 asm("push r9" "\n\t" "push r8" "\n\t" "push r7" "\n\t" "push r6" "\n\t" "push r5");
116 asm("push r4" "\n\t" "push r3" "\n\t" "push r2" "\n\t" "push r1" "\n\t" "push r0");
118 asm("in r0, __SREG__" "\n\t" "push r0");
121 /* Save current context */
123 /* Push ACC first, as when restoring the context it must be restored
124 * last (it is used to set the IE register). */
126 /* Store the IE register then enable interrupts. */
148 if (ao_cur_task_index == AO_NO_TASK_INDEX)
149 ao_cur_task_index = ao_num_tasks-1;
154 asm("in %0,__SP_L__" : "=&r" (sp_l) );
155 asm("in %0,__SP_H__" : "=&r" (sp_h) );
156 ao_cur_task->sp = (uint8_t *) ((uint16_t) sp_l | ((uint16_t) sp_h << 8));
159 __data uint8_t *stack_ptr;
160 __xdata uint8_t *save_ptr;
161 /* Save the current stack */
162 stack_len = SP - (AO_STACK_START - 1);
163 ao_cur_task->stack_count = stack_len;
164 stack_ptr = (uint8_t __data *) AO_STACK_START;
165 save_ptr = (uint8_t __xdata *) ao_cur_task->stack;
167 *save_ptr++ = *stack_ptr++;
173 /* Empty the stack; might as well let interrupts have the whole thing */
174 SP = AO_STACK_START - 1;
177 /* Find a task to run. If there isn't any runnable task,
178 * this loop will run forever, which is just fine
181 __pdata uint8_t ao_next_task_index = ao_cur_task_index;
183 ++ao_next_task_index;
184 if (ao_next_task_index == ao_num_tasks)
185 ao_next_task_index = 0;
187 ao_cur_task = ao_tasks[ao_next_task_index];
188 if (ao_cur_task->wchan == NULL) {
189 ao_cur_task_index = ao_next_task_index;
193 /* Check if the alarm is set for a time which has passed */
194 if (ao_cur_task->alarm &&
195 (int16_t) (ao_time() - ao_cur_task->alarm) >= 0) {
196 ao_cur_task_index = ao_next_task_index;
200 /* Enter lower power mode when there isn't anything to do */
201 if (ao_next_task_index == ao_cur_task_index)
213 sp_l = (uint16_t) ao_cur_task->sp;
214 sp_h = ((uint16_t) ao_cur_task->sp) >> 8;
216 asm("out __SP_H__,%0" : : "r" (sp_h) );
217 asm("out __SP_L__,%0" : : "r" (sp_l) );
220 asm("pop r0" "\n\t" "pop r1" "\n\t" "pop r2" "\n\t" "pop r3" "\n\t" "pop r4");
221 asm("pop r5" "\n\t" "pop r6" "\n\t" "pop r7" "\n\t" "pop r8" "\n\t" "pop r9");
222 asm("pop r10" "\n\t" "pop r11" "\n\t" "pop r12" "\n\t" "pop r13" "\n\t" "pop r14");
223 asm("pop r15" "\n\t" "pop r16" "\n\t" "pop r17" "\n\t" "pop r18" "\n\t" "pop r19");
224 asm("pop r20" "\n\t" "pop r21" "\n\t" "pop r22" "\n\t" "pop r23" "\n\t" "pop r24");
225 asm("pop r25" "\n\t" "pop r26" "\n\t" "pop r27" "\n\t" "pop r28" "\n\t" "pop r29");
226 asm("pop r30" "\n\t" "pop r31");
232 __data uint8_t *stack_ptr;
233 __xdata uint8_t *save_ptr;
235 /* Restore the old stack */
236 stack_len = ao_cur_task->stack_count;
237 SP = AO_STACK_START - 1 + stack_len;
239 stack_ptr = (uint8_t __data *) AO_STACK_START;
240 save_ptr = (uint8_t __xdata *) ao_cur_task->stack;
242 *stack_ptr++ = *save_ptr++;
260 /* The next byte of the stack is the IE register. Only the global
261 enable bit forms part of the task context. Pop off the IE then set
262 the global enable bit to match that of the stored IE register. */
270 /* Finally pop off the ACC, which was the first register saved. */
278 ao_sleep(__xdata void *wchan)
282 ao_cur_task->wchan = wchan;
286 ao_cur_task->alarm = 0;
287 if (ao_cur_task->wchan) {
288 ao_cur_task->wchan = NULL;
295 ao_wakeup(__xdata void *wchan)
299 for (i = 0; i < ao_num_tasks; i++)
300 if (ao_tasks[i]->wchan == wchan)
301 ao_tasks[i]->wchan = NULL;
305 ao_alarm(uint16_t delay)
307 /* Make sure we sleep *at least* delay ticks, which means adding
308 * one to account for the fact that we may be close to the next tick
310 if (!(ao_cur_task->alarm = ao_time() + delay + 1))
311 ao_cur_task->alarm = 1;
315 ao_exit(void) __critical
319 for (i = ao_cur_task_index; i < ao_num_tasks; i++)
320 ao_tasks[i] = ao_tasks[i+1];
321 ao_cur_task_index = AO_NO_TASK_INDEX;
323 /* we'll never get back here */
330 __xdata struct ao_task *task;
332 for (i = 0; i < ao_num_tasks; i++) {
334 printf("%12s: wchan %04x\n",
336 (int16_t) task->wchan);
341 ao_start_scheduler(void)
343 ao_cur_task_index = AO_NO_TASK_INDEX;