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;
28 ao_add_task(__xdata struct ao_task * task, void (*start)(void), __code char *name) __reentrant
30 uint8_t __xdata *stack;
31 if (ao_num_tasks == AO_NUM_TASKS)
32 ao_panic(AO_PANIC_NO_TASK);
33 ao_tasks[ao_num_tasks++] = task;
34 task->task_id = ao_num_tasks;
37 * Construct a stack frame so that it will 'return'
38 * to the start of the task
42 *stack++ = ((uint16_t) start);
43 *stack++ = ((uint16_t) start) >> 8;
45 /* and the stuff saved by ao_switch */
46 *stack++ = 0; /* acc */
47 *stack++ = 0x80; /* IE */
48 *stack++ = 0; /* DPL */
49 *stack++ = 0; /* DPH */
51 *stack++ = 0; /* R2 */
52 *stack++ = 0; /* R3 */
53 *stack++ = 0; /* R4 */
54 *stack++ = 0; /* R5 */
55 *stack++ = 0; /* R6 */
56 *stack++ = 0; /* R7 */
57 *stack++ = 0; /* R0 */
58 *stack++ = 0; /* R1 */
59 *stack++ = 0; /* PSW */
60 *stack++ = 0; /* BP */
61 task->stack_count = stack - task->stack;
65 /* Task switching function. This must not use any stack variables */
70 /* Save current context */
72 /* Push ACC first, as when restoring the context it must be restored
73 * last (it is used to set the IE register). */
75 /* Store the IE register then enable interrupts. */
96 if (ao_cur_task_index == AO_NO_TASK_INDEX)
97 ao_cur_task_index = ao_num_tasks-1;
101 __data uint8_t *stack_ptr;
102 __xdata uint8_t *save_ptr;
103 /* Save the current stack */
104 stack_len = SP - (AO_STACK_START - 1);
105 ao_cur_task->stack_count = stack_len;
106 stack_ptr = (uint8_t __data *) AO_STACK_START;
107 save_ptr = (uint8_t __xdata *) ao_cur_task->stack;
109 *save_ptr++ = *stack_ptr++;
113 /* Empty the stack; might as well let interrupts have the whole thing */
114 SP = AO_STACK_START - 1;
116 /* Find a task to run. If there isn't any runnable task,
117 * this loop will run forever, which is just fine
120 __pdata uint8_t ao_next_task_index = ao_cur_task_index;
122 ++ao_next_task_index;
123 if (ao_next_task_index == ao_num_tasks)
124 ao_next_task_index = 0;
126 ao_cur_task = ao_tasks[ao_next_task_index];
127 if (ao_cur_task->wchan == NULL) {
128 ao_cur_task_index = ao_next_task_index;
132 /* Check if the alarm is set for a time which has passed */
133 if (ao_cur_task->alarm &&
134 (int16_t) (ao_time() - ao_cur_task->alarm) >= 0) {
135 ao_cur_task_index = ao_next_task_index;
139 /* Enter lower power mode when there isn't anything to do */
140 if (ao_next_task_index == ao_cur_task_index)
147 __data uint8_t *stack_ptr;
148 __xdata uint8_t *save_ptr;
150 /* Restore the old stack */
151 stack_len = ao_cur_task->stack_count;
152 SP = AO_STACK_START - 1 + stack_len;
154 stack_ptr = (uint8_t __data *) AO_STACK_START;
155 save_ptr = (uint8_t __xdata *) ao_cur_task->stack;
157 *stack_ptr++ = *save_ptr++;
175 /* The next byte of the stack is the IE register. Only the global
176 enable bit forms part of the task context. Pop off the IE then set
177 the global enable bit to match that of the stored IE register. */
185 /* Finally pop off the ACC, which was the first register saved. */
192 ao_sleep(__xdata void *wchan)
195 ao_cur_task->wchan = wchan;
198 if (ao_cur_task->wchan) {
199 ao_cur_task->wchan = NULL;
200 ao_cur_task->alarm = 0;
203 ao_cur_task->alarm = 0;
208 ao_wakeup(__xdata void *wchan)
212 for (i = 0; i < ao_num_tasks; i++)
213 if (ao_tasks[i]->wchan == wchan)
214 ao_tasks[i]->wchan = NULL;
218 ao_alarm(uint16_t delay)
220 /* Make sure we sleep *at least* delay ticks, which means adding
221 * one to account for the fact that we may be close to the next tick
223 if (!(ao_cur_task->alarm = ao_time() + delay + 1))
224 ao_cur_task->alarm = 1;
228 ao_wake_task(__xdata struct ao_task *task)
234 ao_exit(void) __critical
238 for (i = ao_cur_task_index; i < ao_num_tasks; i++)
239 ao_tasks[i] = ao_tasks[i+1];
240 ao_cur_task_index = AO_NO_TASK_INDEX;
242 /* we'll never get back here */
250 __xdata struct ao_task *task;
252 for (i = 0; i < ao_num_tasks; i++) {
254 pc_loc = task->stack_count - 17;
255 printf("%12s: wchan %04x pc %04x\n",
257 (int16_t) task->wchan,
258 (task->stack[pc_loc]) | (task->stack[pc_loc+1] << 8));
263 ao_start_scheduler(void)
265 ao_cur_task_index = AO_NO_TASK_INDEX;