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