1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * bios-less APM driver for ARM Linux
4 * Jamey Hicks <jamey@crl.dec.com>
5 * adapted from the APM BIOS driver for Linux by Stephen Rothwell (sfr@linuxcare.com)
6 *
7 * APM 1.2 Reference:
8 * Intel Corporation, Microsoft Corporation. Advanced Power Management
9 * (APM) BIOS Interface Specification, Revision 1.2, February 1996.
10 *
11 * This document is available from Microsoft at:
12 * http://www.microsoft.com/whdc/archive/amp_12.mspx
13 */
14 #include <linux/module.h>
15 #include <linux/poll.h>
16 #include <linux/slab.h>
17 #include <linux/mutex.h>
18 #include <linux/proc_fs.h>
19 #include <linux/seq_file.h>
20 #include <linux/miscdevice.h>
21 #include <linux/apm_bios.h>
22 #include <linux/capability.h>
23 #include <linux/sched.h>
24 #include <linux/suspend.h>
25 #include <linux/apm-emulation.h>
26 #include <linux/freezer.h>
27 #include <linux/device.h>
28 #include <linux/kernel.h>
29 #include <linux/list.h>
30 #include <linux/init.h>
31 #include <linux/completion.h>
32 #include <linux/kthread.h>
33 #include <linux/delay.h>
34
35 /*
36 * One option can be changed at boot time as follows:
37 * apm=on/off enable/disable APM
38 */
39
40 /*
41 * Maximum number of events stored
42 */
43 #define APM_MAX_EVENTS 16
44
45 struct apm_queue {
46 unsigned int event_head;
47 unsigned int event_tail;
48 apm_event_t events[APM_MAX_EVENTS];
49 };
50
51 /*
52 * thread states (for threads using a writable /dev/apm_bios fd):
53 *
54 * SUSPEND_NONE: nothing happening
55 * SUSPEND_PENDING: suspend event queued for thread and pending to be read
56 * SUSPEND_READ: suspend event read, pending acknowledgement
57 * SUSPEND_ACKED: acknowledgement received from thread (via ioctl),
58 * waiting for resume
59 * SUSPEND_ACKTO: acknowledgement timeout
60 * SUSPEND_DONE: thread had acked suspend and is now notified of
61 * resume
62 *
63 * SUSPEND_WAIT: this thread invoked suspend and is waiting for resume
64 *
65 * A thread migrates in one of three paths:
66 * NONE -1-> PENDING -2-> READ -3-> ACKED -4-> DONE -5-> NONE
67 * -6-> ACKTO -7-> NONE
68 * NONE -8-> WAIT -9-> NONE
69 *
70 * While in PENDING or READ, the thread is accounted for in the
71 * suspend_acks_pending counter.
72 *
73 * The transitions are invoked as follows:
74 * 1: suspend event is signalled from the core PM code
75 * 2: the suspend event is read from the fd by the userspace thread
76 * 3: userspace thread issues the APM_IOC_SUSPEND ioctl (as ack)
77 * 4: core PM code signals that we have resumed
78 * 5: APM_IOC_SUSPEND ioctl returns
79 *
80 * 6: the notifier invoked from the core PM code timed out waiting
81 * for all relevant threds to enter ACKED state and puts those
82 * that haven't into ACKTO
83 * 7: those threads issue APM_IOC_SUSPEND ioctl too late,
84 * get an error
85 *
86 * 8: userspace thread issues the APM_IOC_SUSPEND ioctl (to suspend),
87 * ioctl code invokes pm_suspend()
88 * 9: pm_suspend() returns indicating resume
89 */
90 enum apm_suspend_state {
91 SUSPEND_NONE,
92 SUSPEND_PENDING,
93 SUSPEND_READ,
94 SUSPEND_ACKED,
95 SUSPEND_ACKTO,
96 SUSPEND_WAIT,
97 SUSPEND_DONE,
98 };
99
100 /*
101 * The per-file APM data
102 */
103 struct apm_user {
104 struct list_head list;
105
106 unsigned int suser: 1;
107 unsigned int writer: 1;
108 unsigned int reader: 1;
109
110 int suspend_result;
111 enum apm_suspend_state suspend_state;
112
113 struct apm_queue queue;
114 };
115
116 /*
117 * Local variables
118 */
119 static atomic_t suspend_acks_pending = ATOMIC_INIT(0);
120 static atomic_t userspace_notification_inhibit = ATOMIC_INIT(0);
121 static int apm_disabled;
122 static struct task_struct *kapmd_tsk;
123
124 static DECLARE_WAIT_QUEUE_HEAD(apm_waitqueue);
125 static DECLARE_WAIT_QUEUE_HEAD(apm_suspend_waitqueue);
126
127 /*
128 * This is a list of everyone who has opened /dev/apm_bios
129 */
130 static DECLARE_RWSEM(user_list_lock);
131 static LIST_HEAD(apm_user_list);
132
133 /*
134 * kapmd info. kapmd provides us a process context to handle
135 * "APM" events within - specifically necessary if we're going
136 * to be suspending the system.
137 */
138 static DECLARE_WAIT_QUEUE_HEAD(kapmd_wait);
139 static DEFINE_SPINLOCK(kapmd_queue_lock);
140 static struct apm_queue kapmd_queue;
141
142 static DEFINE_MUTEX(state_lock);
143
144 static const char driver_version[] = "1.13"; /* no spaces */
145
146
147
148 /*
149 * Compatibility cruft until the IPAQ people move over to the new
150 * interface.
151 */
__apm_get_power_status(struct apm_power_info * info)152 static void __apm_get_power_status(struct apm_power_info *info)
153 {
154 }
155
156 /*
157 * This allows machines to provide their own "apm get power status" function.
158 */
159 void (*apm_get_power_status)(struct apm_power_info *) = __apm_get_power_status;
160 EXPORT_SYMBOL(apm_get_power_status);
161
162
163 /*
164 * APM event queue management.
165 */
queue_empty(struct apm_queue * q)166 static inline int queue_empty(struct apm_queue *q)
167 {
168 return q->event_head == q->event_tail;
169 }
170
queue_get_event(struct apm_queue * q)171 static inline apm_event_t queue_get_event(struct apm_queue *q)
172 {
173 q->event_tail = (q->event_tail + 1) % APM_MAX_EVENTS;
174 return q->events[q->event_tail];
175 }
176
queue_add_event(struct apm_queue * q,apm_event_t event)177 static void queue_add_event(struct apm_queue *q, apm_event_t event)
178 {
179 q->event_head = (q->event_head + 1) % APM_MAX_EVENTS;
180 if (q->event_head == q->event_tail) {
181 static int notified;
182
183 if (notified++ == 0)
184 printk(KERN_ERR "apm: an event queue overflowed\n");
185 q->event_tail = (q->event_tail + 1) % APM_MAX_EVENTS;
186 }
187 q->events[q->event_head] = event;
188 }
189
queue_event(apm_event_t event)190 static void queue_event(apm_event_t event)
191 {
192 struct apm_user *as;
193
194 down_read(&user_list_lock);
195 list_for_each_entry(as, &apm_user_list, list) {
196 if (as->reader)
197 queue_add_event(&as->queue, event);
198 }
199 up_read(&user_list_lock);
200 wake_up_interruptible(&apm_waitqueue);
201 }
202
apm_read(struct file * fp,char __user * buf,size_t count,loff_t * ppos)203 static ssize_t apm_read(struct file *fp, char __user *buf, size_t count, loff_t *ppos)
204 {
205 struct apm_user *as = fp->private_data;
206 apm_event_t event;
207 int i = count, ret = 0;
208
209 if (count < sizeof(apm_event_t))
210 return -EINVAL;
211
212 if (queue_empty(&as->queue) && fp->f_flags & O_NONBLOCK)
213 return -EAGAIN;
214
215 wait_event_interruptible(apm_waitqueue, !queue_empty(&as->queue));
216
217 while ((i >= sizeof(event)) && !queue_empty(&as->queue)) {
218 event = queue_get_event(&as->queue);
219
220 ret = -EFAULT;
221 if (copy_to_user(buf, &event, sizeof(event)))
222 break;
223
224 mutex_lock(&state_lock);
225 if (as->suspend_state == SUSPEND_PENDING &&
226 (event == APM_SYS_SUSPEND || event == APM_USER_SUSPEND))
227 as->suspend_state = SUSPEND_READ;
228 mutex_unlock(&state_lock);
229
230 buf += sizeof(event);
231 i -= sizeof(event);
232 }
233
234 if (i < count)
235 ret = count - i;
236
237 return ret;
238 }
239
apm_poll(struct file * fp,poll_table * wait)240 static __poll_t apm_poll(struct file *fp, poll_table * wait)
241 {
242 struct apm_user *as = fp->private_data;
243
244 poll_wait(fp, &apm_waitqueue, wait);
245 return queue_empty(&as->queue) ? 0 : EPOLLIN | EPOLLRDNORM;
246 }
247
248 /*
249 * apm_ioctl - handle APM ioctl
250 *
251 * APM_IOC_SUSPEND
252 * This IOCTL is overloaded, and performs two functions. It is used to:
253 * - initiate a suspend
254 * - acknowledge a suspend read from /dev/apm_bios.
255 * Only when everyone who has opened /dev/apm_bios with write permission
256 * has acknowledge does the actual suspend happen.
257 */
258 static long
apm_ioctl(struct file * filp,u_int cmd,u_long arg)259 apm_ioctl(struct file *filp, u_int cmd, u_long arg)
260 {
261 struct apm_user *as = filp->private_data;
262 int err = -EINVAL;
263
264 if (!as->suser || !as->writer)
265 return -EPERM;
266
267 switch (cmd) {
268 case APM_IOC_SUSPEND:
269 mutex_lock(&state_lock);
270
271 as->suspend_result = -EINTR;
272
273 switch (as->suspend_state) {
274 case SUSPEND_READ:
275 /*
276 * If we read a suspend command from /dev/apm_bios,
277 * then the corresponding APM_IOC_SUSPEND ioctl is
278 * interpreted as an acknowledge.
279 */
280 as->suspend_state = SUSPEND_ACKED;
281 atomic_dec(&suspend_acks_pending);
282 mutex_unlock(&state_lock);
283
284 /*
285 * suspend_acks_pending changed, the notifier needs to
286 * be woken up for this
287 */
288 wake_up(&apm_suspend_waitqueue);
289
290 /*
291 * Wait for the suspend/resume to complete. If there
292 * are pending acknowledges, we wait here for them.
293 * wait_event_freezable() is interruptible and pending
294 * signal can cause busy looping. We aren't doing
295 * anything critical, chill a bit on each iteration.
296 */
297 while (wait_event_freezable(apm_suspend_waitqueue,
298 as->suspend_state != SUSPEND_ACKED))
299 msleep(10);
300 break;
301 case SUSPEND_ACKTO:
302 as->suspend_result = -ETIMEDOUT;
303 mutex_unlock(&state_lock);
304 break;
305 default:
306 as->suspend_state = SUSPEND_WAIT;
307 mutex_unlock(&state_lock);
308
309 /*
310 * Otherwise it is a request to suspend the system.
311 * Just invoke pm_suspend(), we'll handle it from
312 * there via the notifier.
313 */
314 as->suspend_result = pm_suspend(PM_SUSPEND_MEM);
315 }
316
317 mutex_lock(&state_lock);
318 err = as->suspend_result;
319 as->suspend_state = SUSPEND_NONE;
320 mutex_unlock(&state_lock);
321 break;
322 }
323
324 return err;
325 }
326
apm_release(struct inode * inode,struct file * filp)327 static int apm_release(struct inode * inode, struct file * filp)
328 {
329 struct apm_user *as = filp->private_data;
330
331 filp->private_data = NULL;
332
333 down_write(&user_list_lock);
334 list_del(&as->list);
335 up_write(&user_list_lock);
336
337 /*
338 * We are now unhooked from the chain. As far as new
339 * events are concerned, we no longer exist.
340 */
341 mutex_lock(&state_lock);
342 if (as->suspend_state == SUSPEND_PENDING ||
343 as->suspend_state == SUSPEND_READ)
344 atomic_dec(&suspend_acks_pending);
345 mutex_unlock(&state_lock);
346
347 wake_up(&apm_suspend_waitqueue);
348
349 kfree(as);
350 return 0;
351 }
352
apm_open(struct inode * inode,struct file * filp)353 static int apm_open(struct inode * inode, struct file * filp)
354 {
355 struct apm_user *as;
356
357 as = kzalloc(sizeof(*as), GFP_KERNEL);
358 if (as) {
359 /*
360 * XXX - this is a tiny bit broken, when we consider BSD
361 * process accounting. If the device is opened by root, we
362 * instantly flag that we used superuser privs. Who knows,
363 * we might close the device immediately without doing a
364 * privileged operation -- cevans
365 */
366 as->suser = capable(CAP_SYS_ADMIN);
367 as->writer = (filp->f_mode & FMODE_WRITE) == FMODE_WRITE;
368 as->reader = (filp->f_mode & FMODE_READ) == FMODE_READ;
369
370 down_write(&user_list_lock);
371 list_add(&as->list, &apm_user_list);
372 up_write(&user_list_lock);
373
374 filp->private_data = as;
375 }
376
377 return as ? 0 : -ENOMEM;
378 }
379
380 static const struct file_operations apm_bios_fops = {
381 .owner = THIS_MODULE,
382 .read = apm_read,
383 .poll = apm_poll,
384 .unlocked_ioctl = apm_ioctl,
385 .open = apm_open,
386 .release = apm_release,
387 .llseek = noop_llseek,
388 };
389
390 static struct miscdevice apm_device = {
391 .minor = APM_MINOR_DEV,
392 .name = "apm_bios",
393 .fops = &apm_bios_fops
394 };
395
396
397 #ifdef CONFIG_PROC_FS
398 /*
399 * Arguments, with symbols from linux/apm_bios.h.
400 *
401 * 0) Linux driver version (this will change if format changes)
402 * 1) APM BIOS Version. Usually 1.0, 1.1 or 1.2.
403 * 2) APM flags from APM Installation Check (0x00):
404 * bit 0: APM_16_BIT_SUPPORT
405 * bit 1: APM_32_BIT_SUPPORT
406 * bit 2: APM_IDLE_SLOWS_CLOCK
407 * bit 3: APM_BIOS_DISABLED
408 * bit 4: APM_BIOS_DISENGAGED
409 * 3) AC line status
410 * 0x00: Off-line
411 * 0x01: On-line
412 * 0x02: On backup power (BIOS >= 1.1 only)
413 * 0xff: Unknown
414 * 4) Battery status
415 * 0x00: High
416 * 0x01: Low
417 * 0x02: Critical
418 * 0x03: Charging
419 * 0x04: Selected battery not present (BIOS >= 1.2 only)
420 * 0xff: Unknown
421 * 5) Battery flag
422 * bit 0: High
423 * bit 1: Low
424 * bit 2: Critical
425 * bit 3: Charging
426 * bit 7: No system battery
427 * 0xff: Unknown
428 * 6) Remaining battery life (percentage of charge):
429 * 0-100: valid
430 * -1: Unknown
431 * 7) Remaining battery life (time units):
432 * Number of remaining minutes or seconds
433 * -1: Unknown
434 * 8) min = minutes; sec = seconds
435 */
proc_apm_show(struct seq_file * m,void * v)436 static int proc_apm_show(struct seq_file *m, void *v)
437 {
438 struct apm_power_info info;
439 char *units;
440
441 info.ac_line_status = 0xff;
442 info.battery_status = 0xff;
443 info.battery_flag = 0xff;
444 info.battery_life = -1;
445 info.time = -1;
446 info.units = -1;
447
448 if (apm_get_power_status)
449 apm_get_power_status(&info);
450
451 switch (info.units) {
452 default: units = "?"; break;
453 case 0: units = "min"; break;
454 case 1: units = "sec"; break;
455 }
456
457 seq_printf(m, "%s 1.2 0x%02x 0x%02x 0x%02x 0x%02x %d%% %d %s\n",
458 driver_version, APM_32_BIT_SUPPORT,
459 info.ac_line_status, info.battery_status,
460 info.battery_flag, info.battery_life,
461 info.time, units);
462
463 return 0;
464 }
465 #endif
466
kapmd(void * arg)467 static int kapmd(void *arg)
468 {
469 do {
470 apm_event_t event;
471
472 wait_event_interruptible(kapmd_wait,
473 !queue_empty(&kapmd_queue) || kthread_should_stop());
474
475 if (kthread_should_stop())
476 break;
477
478 spin_lock_irq(&kapmd_queue_lock);
479 event = 0;
480 if (!queue_empty(&kapmd_queue))
481 event = queue_get_event(&kapmd_queue);
482 spin_unlock_irq(&kapmd_queue_lock);
483
484 switch (event) {
485 case 0:
486 break;
487
488 case APM_LOW_BATTERY:
489 case APM_POWER_STATUS_CHANGE:
490 queue_event(event);
491 break;
492
493 case APM_USER_SUSPEND:
494 case APM_SYS_SUSPEND:
495 pm_suspend(PM_SUSPEND_MEM);
496 break;
497
498 case APM_CRITICAL_SUSPEND:
499 atomic_inc(&userspace_notification_inhibit);
500 pm_suspend(PM_SUSPEND_MEM);
501 atomic_dec(&userspace_notification_inhibit);
502 break;
503 }
504 } while (1);
505
506 return 0;
507 }
508
apm_suspend_notifier(struct notifier_block * nb,unsigned long event,void * dummy)509 static int apm_suspend_notifier(struct notifier_block *nb,
510 unsigned long event,
511 void *dummy)
512 {
513 struct apm_user *as;
514 int err;
515 unsigned long apm_event;
516
517 /* short-cut emergency suspends */
518 if (atomic_read(&userspace_notification_inhibit))
519 return NOTIFY_DONE;
520
521 switch (event) {
522 case PM_SUSPEND_PREPARE:
523 case PM_HIBERNATION_PREPARE:
524 apm_event = (event == PM_SUSPEND_PREPARE) ?
525 APM_USER_SUSPEND : APM_USER_HIBERNATION;
526 /*
527 * Queue an event to all "writer" users that we want
528 * to suspend and need their ack.
529 */
530 mutex_lock(&state_lock);
531 down_read(&user_list_lock);
532
533 list_for_each_entry(as, &apm_user_list, list) {
534 if (as->suspend_state != SUSPEND_WAIT && as->reader &&
535 as->writer && as->suser) {
536 as->suspend_state = SUSPEND_PENDING;
537 atomic_inc(&suspend_acks_pending);
538 queue_add_event(&as->queue, apm_event);
539 }
540 }
541
542 up_read(&user_list_lock);
543 mutex_unlock(&state_lock);
544 wake_up_interruptible(&apm_waitqueue);
545
546 /*
547 * Wait for the the suspend_acks_pending variable to drop to
548 * zero, meaning everybody acked the suspend event (or the
549 * process was killed.)
550 *
551 * If the app won't answer within a short while we assume it
552 * locked up and ignore it.
553 */
554 err = wait_event_interruptible_timeout(
555 apm_suspend_waitqueue,
556 atomic_read(&suspend_acks_pending) == 0,
557 5*HZ);
558
559 /* timed out */
560 if (err == 0) {
561 /*
562 * Move anybody who timed out to "ack timeout" state.
563 *
564 * We could time out and the userspace does the ACK
565 * right after we time out but before we enter the
566 * locked section here, but that's fine.
567 */
568 mutex_lock(&state_lock);
569 down_read(&user_list_lock);
570 list_for_each_entry(as, &apm_user_list, list) {
571 if (as->suspend_state == SUSPEND_PENDING ||
572 as->suspend_state == SUSPEND_READ) {
573 as->suspend_state = SUSPEND_ACKTO;
574 atomic_dec(&suspend_acks_pending);
575 }
576 }
577 up_read(&user_list_lock);
578 mutex_unlock(&state_lock);
579 }
580
581 /* let suspend proceed */
582 if (err >= 0)
583 return NOTIFY_OK;
584
585 /* interrupted by signal */
586 return notifier_from_errno(err);
587
588 case PM_POST_SUSPEND:
589 case PM_POST_HIBERNATION:
590 apm_event = (event == PM_POST_SUSPEND) ?
591 APM_NORMAL_RESUME : APM_HIBERNATION_RESUME;
592 /*
593 * Anyone on the APM queues will think we're still suspended.
594 * Send a message so everyone knows we're now awake again.
595 */
596 queue_event(apm_event);
597
598 /*
599 * Finally, wake up anyone who is sleeping on the suspend.
600 */
601 mutex_lock(&state_lock);
602 down_read(&user_list_lock);
603 list_for_each_entry(as, &apm_user_list, list) {
604 if (as->suspend_state == SUSPEND_ACKED) {
605 /*
606 * TODO: maybe grab error code, needs core
607 * changes to push the error to the notifier
608 * chain (could use the second parameter if
609 * implemented)
610 */
611 as->suspend_result = 0;
612 as->suspend_state = SUSPEND_DONE;
613 }
614 }
615 up_read(&user_list_lock);
616 mutex_unlock(&state_lock);
617
618 wake_up(&apm_suspend_waitqueue);
619 return NOTIFY_OK;
620
621 default:
622 return NOTIFY_DONE;
623 }
624 }
625
626 static struct notifier_block apm_notif_block = {
627 .notifier_call = apm_suspend_notifier,
628 };
629
apm_init(void)630 static int __init apm_init(void)
631 {
632 int ret;
633
634 if (apm_disabled) {
635 printk(KERN_NOTICE "apm: disabled on user request.\n");
636 return -ENODEV;
637 }
638
639 kapmd_tsk = kthread_create(kapmd, NULL, "kapmd");
640 if (IS_ERR(kapmd_tsk)) {
641 ret = PTR_ERR(kapmd_tsk);
642 kapmd_tsk = NULL;
643 goto out;
644 }
645 wake_up_process(kapmd_tsk);
646
647 #ifdef CONFIG_PROC_FS
648 proc_create_single("apm", 0, NULL, proc_apm_show);
649 #endif
650
651 ret = misc_register(&apm_device);
652 if (ret)
653 goto out_stop;
654
655 ret = register_pm_notifier(&apm_notif_block);
656 if (ret)
657 goto out_unregister;
658
659 return 0;
660
661 out_unregister:
662 misc_deregister(&apm_device);
663 out_stop:
664 remove_proc_entry("apm", NULL);
665 kthread_stop(kapmd_tsk);
666 out:
667 return ret;
668 }
669
apm_exit(void)670 static void __exit apm_exit(void)
671 {
672 unregister_pm_notifier(&apm_notif_block);
673 misc_deregister(&apm_device);
674 remove_proc_entry("apm", NULL);
675
676 kthread_stop(kapmd_tsk);
677 }
678
679 module_init(apm_init);
680 module_exit(apm_exit);
681
682 MODULE_AUTHOR("Stephen Rothwell");
683 MODULE_DESCRIPTION("Advanced Power Management");
684 MODULE_LICENSE("GPL");
685
686 #ifndef MODULE
apm_setup(char * str)687 static int __init apm_setup(char *str)
688 {
689 while ((str != NULL) && (*str != '\0')) {
690 if (strncmp(str, "off", 3) == 0)
691 apm_disabled = 1;
692 if (strncmp(str, "on", 2) == 0)
693 apm_disabled = 0;
694 str = strchr(str, ',');
695 if (str != NULL)
696 str += strspn(str, ", \t");
697 }
698 return 1;
699 }
700
701 __setup("apm=", apm_setup);
702 #endif
703
704 /**
705 * apm_queue_event - queue an APM event for kapmd
706 * @event: APM event
707 *
708 * Queue an APM event for kapmd to process and ultimately take the
709 * appropriate action. Only a subset of events are handled:
710 * %APM_LOW_BATTERY
711 * %APM_POWER_STATUS_CHANGE
712 * %APM_USER_SUSPEND
713 * %APM_SYS_SUSPEND
714 * %APM_CRITICAL_SUSPEND
715 */
apm_queue_event(apm_event_t event)716 void apm_queue_event(apm_event_t event)
717 {
718 unsigned long flags;
719
720 spin_lock_irqsave(&kapmd_queue_lock, flags);
721 queue_add_event(&kapmd_queue, event);
722 spin_unlock_irqrestore(&kapmd_queue_lock, flags);
723
724 wake_up_interruptible(&kapmd_wait);
725 }
726 EXPORT_SYMBOL(apm_queue_event);
727
