summaryrefslogtreecommitdiff
path: root/drivers/gpu/vga/vga_switcheroo.c
blob: d64d9058bce57ef6b424c994c02ff7f6cb36baa5 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
/*
 * vga_switcheroo.c - Support for laptop with dual GPU using one set of outputs
 *
 * Copyright (c) 2010 Red Hat Inc.
 * Author : Dave Airlie <airlied@redhat.com>
 *
 * Copyright (c) 2015 Lukas Wunner <lukas@wunner.de>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS
 * IN THE SOFTWARE.
 *
 */

#define pr_fmt(fmt) "vga_switcheroo: " fmt

#include <linux/console.h>
#include <linux/debugfs.h>
#include <linux/fb.h>
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/pm_runtime.h>
#include <linux/seq_file.h>
#include <linux/uaccess.h>
#include <linux/vgaarb.h>
#include <linux/vga_switcheroo.h>

/**
 * DOC: Overview
 *
 * vga_switcheroo is the Linux subsystem for laptop hybrid graphics.
 * These come in two flavors:
 *
 * * muxed: Dual GPUs with a multiplexer chip to switch outputs between GPUs.
 * * muxless: Dual GPUs but only one of them is connected to outputs.
 * 	The other one is merely used to offload rendering, its results
 * 	are copied over PCIe into the framebuffer. On Linux this is
 * 	supported with DRI PRIME.
 *
 * Hybrid graphics started to appear in the late Naughties and were initially
 * all muxed. Newer laptops moved to a muxless architecture for cost reasons.
 * A notable exception is the MacBook Pro which continues to use a mux.
 * Muxes come with varying capabilities: Some switch only the panel, others
 * can also switch external displays. Some switch all display pins at once
 * while others can switch just the DDC lines. (To allow EDID probing
 * for the inactive GPU.) Also, muxes are often used to cut power to the
 * discrete GPU while it is not used.
 *
 * DRM drivers register GPUs with vga_switcheroo, these are henceforth called
 * clients. The mux is called the handler. Muxless machines also register a
 * handler to control the power state of the discrete GPU, its ->switchto
 * callback is a no-op for obvious reasons. The discrete GPU is often equipped
 * with an HDA controller for the HDMI/DP audio signal, this will also
 * register as a client so that vga_switcheroo can take care of the correct
 * suspend/resume order when changing the discrete GPU's power state. In total
 * there can thus be up to three clients: Two vga clients (GPUs) and one audio
 * client (on the discrete GPU). The code is mostly prepared to support
 * machines with more than two GPUs should they become available.
 * The GPU to which the outputs are currently switched is called the
 * active client in vga_switcheroo parlance. The GPU not in use is the
 * inactive client.
 */

/**
 * struct vga_switcheroo_client - registered client
 * @pdev: client pci device
 * @fb_info: framebuffer to which console is remapped on switching
 * @pwr_state: current power state
 * @ops: client callbacks
 * @id: client identifier. Determining the id requires the handler,
 * 	so gpus are initially assigned VGA_SWITCHEROO_UNKNOWN_ID
 * 	and later given their true id in vga_switcheroo_enable()
 * @active: whether the outputs are currently switched to this client
 * @driver_power_control: whether power state is controlled by the driver's
 * 	runtime pm. If true, writing ON and OFF to the vga_switcheroo debugfs
 * 	interface is a no-op so as not to interfere with runtime pm
 * @list: client list
 *
 * Registered client. A client can be either a GPU or an audio device on a GPU.
 * For audio clients, the @fb_info, @active and @driver_power_control members
 * are bogus.
 */
struct vga_switcheroo_client {
	struct pci_dev *pdev;
	struct fb_info *fb_info;
	enum vga_switcheroo_state pwr_state;
	const struct vga_switcheroo_client_ops *ops;
	enum vga_switcheroo_client_id id;
	bool active;
	bool driver_power_control;
	struct list_head list;
};

/*
 * protects access to struct vgasr_priv
 */
static DEFINE_MUTEX(vgasr_mutex);

/**
 * struct vgasr_priv - vga_switcheroo private data
 * @active: whether vga_switcheroo is enabled.
 * 	Prerequisite is the registration of two GPUs and a handler
 * @delayed_switch_active: whether a delayed switch is pending
 * @delayed_client_id: client to which a delayed switch is pending
 * @debugfs_root: directory for vga_switcheroo debugfs interface
 * @switch_file: file for vga_switcheroo debugfs interface
 * @registered_clients: number of registered GPUs
 * 	(counting only vga clients, not audio clients)
 * @clients: list of registered clients
 * @handler: registered handler
 *
 * vga_switcheroo private data. Currently only one vga_switcheroo instance
 * per system is supported.
 */
struct vgasr_priv {
	bool active;
	bool delayed_switch_active;
	enum vga_switcheroo_client_id delayed_client_id;

	struct dentry *debugfs_root;
	struct dentry *switch_file;

	int registered_clients;
	struct list_head clients;

	const struct vga_switcheroo_handler *handler;
};

#define ID_BIT_AUDIO		0x100
#define client_is_audio(c)	((c)->id & ID_BIT_AUDIO)
#define client_is_vga(c)	((c)->id == VGA_SWITCHEROO_UNKNOWN_ID || \
				 !client_is_audio(c))
#define client_id(c)		((c)->id & ~ID_BIT_AUDIO)

static int vga_switcheroo_debugfs_init(struct vgasr_priv *priv);
static void vga_switcheroo_debugfs_fini(struct vgasr_priv *priv);

/* only one switcheroo per system */
static struct vgasr_priv vgasr_priv = {
	.clients = LIST_HEAD_INIT(vgasr_priv.clients),
};

static bool vga_switcheroo_ready(void)
{
	/* we're ready if we get two clients + handler */
	return !vgasr_priv.active &&
	       vgasr_priv.registered_clients == 2 && vgasr_priv.handler;
}

static void vga_switcheroo_enable(void)
{
	int ret;
	struct vga_switcheroo_client *client;

	/* call the handler to init */
	if (vgasr_priv.handler->init)
		vgasr_priv.handler->init();

	list_for_each_entry(client, &vgasr_priv.clients, list) {
		if (client->id != VGA_SWITCHEROO_UNKNOWN_ID)
			continue;
		ret = vgasr_priv.handler->get_client_id(client->pdev);
		if (ret < 0)
			return;

		client->id = ret;
	}
	vga_switcheroo_debugfs_init(&vgasr_priv);
	vgasr_priv.active = true;
}

/**
 * vga_switcheroo_register_handler() - register handler
 * @handler: handler callbacks
 *
 * Register handler. Enable vga_switcheroo if two vga clients have already
 * registered.
 *
 * Return: 0 on success, -EINVAL if a handler was already registered.
 */
int vga_switcheroo_register_handler(const struct vga_switcheroo_handler *handler)
{
	mutex_lock(&vgasr_mutex);
	if (vgasr_priv.handler) {
		mutex_unlock(&vgasr_mutex);
		return -EINVAL;
	}

	vgasr_priv.handler = handler;
	if (vga_switcheroo_ready()) {
		pr_info("enabled\n");
		vga_switcheroo_enable();
	}
	mutex_unlock(&vgasr_mutex);
	return 0;
}
EXPORT_SYMBOL(vga_switcheroo_register_handler);

/**
 * vga_switcheroo_unregister_handler() - unregister handler
 *
 * Unregister handler. Disable vga_switcheroo.
 */
void vga_switcheroo_unregister_handler(void)
{
	mutex_lock(&vgasr_mutex);
	vgasr_priv.handler = NULL;
	if (vgasr_priv.active) {
		pr_info("disabled\n");
		vga_switcheroo_debugfs_fini(&vgasr_priv);
		vgasr_priv.active = false;
	}
	mutex_unlock(&vgasr_mutex);
}
EXPORT_SYMBOL(vga_switcheroo_unregister_handler);

static int register_client(struct pci_dev *pdev,
			   const struct vga_switcheroo_client_ops *ops,
			   enum vga_switcheroo_client_id id, bool active,
			   bool driver_power_control)
{
	struct vga_switcheroo_client *client;

	client = kzalloc(sizeof(*client), GFP_KERNEL);
	if (!client)
		return -ENOMEM;

	client->pwr_state = VGA_SWITCHEROO_ON;
	client->pdev = pdev;
	client->ops = ops;
	client->id = id;
	client->active = active;
	client->driver_power_control = driver_power_control;

	mutex_lock(&vgasr_mutex);
	list_add_tail(&client->list, &vgasr_priv.clients);
	if (client_is_vga(client))
		vgasr_priv.registered_clients++;

	if (vga_switcheroo_ready()) {
		pr_info("enabled\n");
		vga_switcheroo_enable();
	}
	mutex_unlock(&vgasr_mutex);
	return 0;
}

/**
 * vga_switcheroo_register_client - register vga client
 * @pdev: client pci device
 * @ops: client callbacks
 * @driver_power_control: whether power state is controlled by the driver's
 * 	runtime pm
 *
 * Register vga client (GPU). Enable vga_switcheroo if another GPU and a
 * handler have already registered. The power state of the client is assumed
 * to be ON.
 *
 * Return: 0 on success, -ENOMEM on memory allocation error.
 */
int vga_switcheroo_register_client(struct pci_dev *pdev,
				   const struct vga_switcheroo_client_ops *ops,
				   bool driver_power_control)
{
	return register_client(pdev, ops, VGA_SWITCHEROO_UNKNOWN_ID,
			       pdev == vga_default_device(),
			       driver_power_control);
}
EXPORT_SYMBOL(vga_switcheroo_register_client);

/**
 * vga_switcheroo_register_audio_client - register audio client
 * @pdev: client pci device
 * @ops: client callbacks
 * @id: client identifier
 *
 * Register audio client (audio device on a GPU). The power state of the
 * client is assumed to be ON.
 *
 * Return: 0 on success, -ENOMEM on memory allocation error.
 */
int vga_switcheroo_register_audio_client(struct pci_dev *pdev,
					 const struct vga_switcheroo_client_ops *ops,
					 enum vga_switcheroo_client_id id)
{
	return register_client(pdev, ops, id | ID_BIT_AUDIO, false, false);
}
EXPORT_SYMBOL(vga_switcheroo_register_audio_client);

static struct vga_switcheroo_client *
find_client_from_pci(struct list_head *head, struct pci_dev *pdev)
{
	struct vga_switcheroo_client *client;

	list_for_each_entry(client, head, list)
		if (client->pdev == pdev)
			return client;
	return NULL;
}

static struct vga_switcheroo_client *
find_client_from_id(struct list_head *head,
		    enum vga_switcheroo_client_id client_id)
{
	struct vga_switcheroo_client *client;

	list_for_each_entry(client, head, list)
		if (client->id == client_id)
			return client;
	return NULL;
}

static struct vga_switcheroo_client *
find_active_client(struct list_head *head)
{
	struct vga_switcheroo_client *client;

	list_for_each_entry(client, head, list)
		if (client->active)
			return client;
	return NULL;
}

/**
 * vga_switcheroo_get_client_state() - obtain power state of a given client
 * @pdev: client pci device
 *
 * Obtain power state of a given client as seen from vga_switcheroo.
 * The function is only called from hda_intel.c.
 *
 * Return: Power state.
 */
enum vga_switcheroo_state vga_switcheroo_get_client_state(struct pci_dev *pdev)
{
	struct vga_switcheroo_client *client;
	enum vga_switcheroo_state ret;

	mutex_lock(&vgasr_mutex);
	client = find_client_from_pci(&vgasr_priv.clients, pdev);
	if (!client)
		ret = VGA_SWITCHEROO_NOT_FOUND;
	else
		ret = client->pwr_state;
	mutex_unlock(&vgasr_mutex);
	return ret;
}
EXPORT_SYMBOL(vga_switcheroo_get_client_state);

/**
 * vga_switcheroo_unregister_client() - unregister client
 * @pdev: client pci device
 *
 * Unregister client. Disable vga_switcheroo if this is a vga client (GPU).
 */
void vga_switcheroo_unregister_client(struct pci_dev *pdev)
{
	struct vga_switcheroo_client *client;

	mutex_lock(&vgasr_mutex);
	client = find_client_from_pci(&vgasr_priv.clients, pdev);
	if (client) {
		if (client_is_vga(client))
			vgasr_priv.registered_clients--;
		list_del(&client->list);
		kfree(client);
	}
	if (vgasr_priv.active && vgasr_priv.registered_clients < 2) {
		pr_info("disabled\n");
		vga_switcheroo_debugfs_fini(&vgasr_priv);
		vgasr_priv.active = false;
	}
	mutex_unlock(&vgasr_mutex);
}
EXPORT_SYMBOL(vga_switcheroo_unregister_client);

/**
 * vga_switcheroo_client_fb_set() - set framebuffer of a given client
 * @pdev: client pci device
 * @info: framebuffer
 *
 * Set framebuffer of a given client. The console will be remapped to this
 * on switching.
 */
void vga_switcheroo_client_fb_set(struct pci_dev *pdev,
				 struct fb_info *info)
{
	struct vga_switcheroo_client *client;

	mutex_lock(&vgasr_mutex);
	client = find_client_from_pci(&vgasr_priv.clients, pdev);
	if (client)
		client->fb_info = info;
	mutex_unlock(&vgasr_mutex);
}
EXPORT_SYMBOL(vga_switcheroo_client_fb_set);

/**
 * DOC: Manual switching and manual power control
 *
 * In this mode of use, the file /sys/kernel/debug/vgaswitcheroo/switch
 * can be read to retrieve the current vga_switcheroo state and commands
 * can be written to it to change the state. The file appears as soon as
 * two GPU drivers and one handler have registered with vga_switcheroo.
 * The following commands are understood:
 *
 * * OFF: Power off the device not in use.
 * * ON: Power on the device not in use.
 * * IGD: Switch to the integrated graphics device.
 * 	Power on the integrated GPU if necessary, power off the discrete GPU.
 * 	Prerequisite is that no user space processes (e.g. Xorg, alsactl)
 * 	have opened device files of the GPUs or the audio client. If the
 * 	switch fails, the user may invoke lsof(8) or fuser(1) on /dev/dri/
 * 	and /dev/snd/controlC1 to identify processes blocking the switch.
 * * DIS: Switch to the discrete graphics device.
 * * DIGD: Delayed switch to the integrated graphics device.
 * 	This will perform the switch once the last user space process has
 * 	closed the device files of the GPUs and the audio client.
 * * DDIS: Delayed switch to the discrete graphics device.
 * * MIGD: Mux-only switch to the integrated graphics device.
 * 	Does not remap console or change the power state of either gpu.
 * 	If the integrated GPU is currently off, the screen will turn black.
 * 	If it is on, the screen will show whatever happens to be in VRAM.
 * 	Either way, the user has to blindly enter the command to switch back.
 * * MDIS: Mux-only switch to the discrete graphics device.
 *
 * For GPUs whose power state is controlled by the driver's runtime pm,
 * the ON and OFF commands are a no-op (see next section).
 *
 * For muxless machines, the IGD/DIS, DIGD/DDIS and MIGD/MDIS commands
 * should not be used.
 */

static int vga_switcheroo_show(struct seq_file *m, void *v)
{
	struct vga_switcheroo_client *client;
	int i = 0;

	mutex_lock(&vgasr_mutex);
	list_for_each_entry(client, &vgasr_priv.clients, list) {
		seq_printf(m, "%d:%s%s:%c:%s%s:%s\n", i,
			   client_id(client) == VGA_SWITCHEROO_DIS ? "DIS" :
								     "IGD",
			   client_is_vga(client) ? "" : "-Audio",
			   client->active ? '+' : ' ',
			   client->driver_power_control ? "Dyn" : "",
			   client->pwr_state ? "Pwr" : "Off",
			   pci_name(client->pdev));
		i++;
	}
	mutex_unlock(&vgasr_mutex);
	return 0;
}

static int vga_switcheroo_debugfs_open(struct inode *inode, struct file *file)
{
	return single_open(file, vga_switcheroo_show, NULL);
}

static int vga_switchon(struct vga_switcheroo_client *client)
{
	if (client->driver_power_control)
		return 0;
	if (vgasr_priv.handler->power_state)
		vgasr_priv.handler->power_state(client->id, VGA_SWITCHEROO_ON);
	/* call the driver callback to turn on device */
	client->ops->set_gpu_state(client->pdev, VGA_SWITCHEROO_ON);
	client->pwr_state = VGA_SWITCHEROO_ON;
	return 0;
}

static int vga_switchoff(struct vga_switcheroo_client *client)
{
	if (client->driver_power_control)
		return 0;
	/* call the driver callback to turn off device */
	client->ops->set_gpu_state(client->pdev, VGA_SWITCHEROO_OFF);
	if (vgasr_priv.handler->power_state)
		vgasr_priv.handler->power_state(client->id, VGA_SWITCHEROO_OFF);
	client->pwr_state = VGA_SWITCHEROO_OFF;
	return 0;
}

static void set_audio_state(enum vga_switcheroo_client_id id,
			    enum vga_switcheroo_state state)
{
	struct vga_switcheroo_client *client;

	client = find_client_from_id(&vgasr_priv.clients, id | ID_BIT_AUDIO);
	if (client && client->pwr_state != state) {
		client->ops->set_gpu_state(client->pdev, state);
		client->pwr_state = state;
	}
}

/* stage one happens before delay */
static int vga_switchto_stage1(struct vga_switcheroo_client *new_client)
{
	struct vga_switcheroo_client *active;

	active = find_active_client(&vgasr_priv.clients);
	if (!active)
		return 0;

	if (new_client->pwr_state == VGA_SWITCHEROO_OFF)
		vga_switchon(new_client);

	vga_set_default_device(new_client->pdev);
	return 0;
}

/* post delay */
static int vga_switchto_stage2(struct vga_switcheroo_client *new_client)
{
	int ret;
	struct vga_switcheroo_client *active;

	active = find_active_client(&vgasr_priv.clients);
	if (!active)
		return 0;

	active->active = false;

	set_audio_state(active->id, VGA_SWITCHEROO_OFF);

	if (new_client->fb_info) {
		struct fb_event event;

		console_lock();
		event.info = new_client->fb_info;
		fb_notifier_call_chain(FB_EVENT_REMAP_ALL_CONSOLE, &event);
		console_unlock();
	}

	ret = vgasr_priv.handler->switchto(new_client->id);
	if (ret)
		return ret;

	if (new_client->ops->reprobe)
		new_client->ops->reprobe(new_client->pdev);

	if (active->pwr_state == VGA_SWITCHEROO_ON)
		vga_switchoff(active);

	set_audio_state(new_client->id, VGA_SWITCHEROO_ON);

	new_client->active = true;
	return 0;
}

static bool check_can_switch(void)
{
	struct vga_switcheroo_client *client;

	list_for_each_entry(client, &vgasr_priv.clients, list) {
		if (!client->ops->can_switch(client->pdev)) {
			pr_err("client %x refused switch\n", client->id);
			return false;
		}
	}
	return true;
}

static ssize_t
vga_switcheroo_debugfs_write(struct file *filp, const char __user *ubuf,
			     size_t cnt, loff_t *ppos)
{
	char usercmd[64];
	int ret;
	bool delay = false, can_switch;
	bool just_mux = false;
	enum vga_switcheroo_client_id client_id = VGA_SWITCHEROO_UNKNOWN_ID;
	struct vga_switcheroo_client *client = NULL;

	if (cnt > 63)
		cnt = 63;

	if (copy_from_user(usercmd, ubuf, cnt))
		return -EFAULT;

	mutex_lock(&vgasr_mutex);

	if (!vgasr_priv.active) {
		cnt = -EINVAL;
		goto out;
	}

	/* pwr off the device not in use */
	if (strncmp(usercmd, "OFF", 3) == 0) {
		list_for_each_entry(client, &vgasr_priv.clients, list) {
			if (client->active || client_is_audio(client))
				continue;
			if (client->driver_power_control)
				continue;
			set_audio_state(client->id, VGA_SWITCHEROO_OFF);
			if (client->pwr_state == VGA_SWITCHEROO_ON)
				vga_switchoff(client);
		}
		goto out;
	}
	/* pwr on the device not in use */
	if (strncmp(usercmd, "ON", 2) == 0) {
		list_for_each_entry(client, &vgasr_priv.clients, list) {
			if (client->active || client_is_audio(client))
				continue;
			if (client->driver_power_control)
				continue;
			if (client->pwr_state == VGA_SWITCHEROO_OFF)
				vga_switchon(client);
			set_audio_state(client->id, VGA_SWITCHEROO_ON);
		}
		goto out;
	}

	/* request a delayed switch - test can we switch now */
	if (strncmp(usercmd, "DIGD", 4) == 0) {
		client_id = VGA_SWITCHEROO_IGD;
		delay = true;
	}

	if (strncmp(usercmd, "DDIS", 4) == 0) {
		client_id = VGA_SWITCHEROO_DIS;
		delay = true;
	}

	if (strncmp(usercmd, "IGD", 3) == 0)
		client_id = VGA_SWITCHEROO_IGD;

	if (strncmp(usercmd, "DIS", 3) == 0)
		client_id = VGA_SWITCHEROO_DIS;

	if (strncmp(usercmd, "MIGD", 4) == 0) {
		just_mux = true;
		client_id = VGA_SWITCHEROO_IGD;
	}
	if (strncmp(usercmd, "MDIS", 4) == 0) {
		just_mux = true;
		client_id = VGA_SWITCHEROO_DIS;
	}

	if (client_id == VGA_SWITCHEROO_UNKNOWN_ID)
		goto out;
	client = find_client_from_id(&vgasr_priv.clients, client_id);
	if (!client)
		goto out;

	vgasr_priv.delayed_switch_active = false;

	if (just_mux) {
		ret = vgasr_priv.handler->switchto(client_id);
		goto out;
	}

	if (client->active)
		goto out;

	/* okay we want a switch - test if devices are willing to switch */
	can_switch = check_can_switch();

	if (can_switch == false && delay == false)
		goto out;

	if (can_switch) {
		ret = vga_switchto_stage1(client);
		if (ret)
			pr_err("switching failed stage 1 %d\n", ret);

		ret = vga_switchto_stage2(client);
		if (ret)
			pr_err("switching failed stage 2 %d\n", ret);

	} else {
		pr_info("setting delayed switch to client %d\n", client->id);
		vgasr_priv.delayed_switch_active = true;
		vgasr_priv.delayed_client_id = client_id;

		ret = vga_switchto_stage1(client);
		if (ret)
			pr_err("delayed switching stage 1 failed %d\n", ret);
	}

out:
	mutex_unlock(&vgasr_mutex);
	return cnt;
}

static const struct file_operations vga_switcheroo_debugfs_fops = {
	.owner = THIS_MODULE,
	.open = vga_switcheroo_debugfs_open,
	.write = vga_switcheroo_debugfs_write,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
};

static void vga_switcheroo_debugfs_fini(struct vgasr_priv *priv)
{
	debugfs_remove(priv->switch_file);
	priv->switch_file = NULL;

	debugfs_remove(priv->debugfs_root);
	priv->debugfs_root = NULL;
}

static int vga_switcheroo_debugfs_init(struct vgasr_priv *priv)
{
	static const char mp[] = "/sys/kernel/debug";

	/* already initialised */
	if (priv->debugfs_root)
		return 0;
	priv->debugfs_root = debugfs_create_dir("vgaswitcheroo", NULL);

	if (!priv->debugfs_root) {
		pr_err("Cannot create %s/vgaswitcheroo\n", mp);
		goto fail;
	}

	priv->switch_file = debugfs_create_file("switch", 0644,
						priv->debugfs_root, NULL,
						&vga_switcheroo_debugfs_fops);
	if (!priv->switch_file) {
		pr_err("cannot create %s/vgaswitcheroo/switch\n", mp);
		goto fail;
	}
	return 0;
fail:
	vga_switcheroo_debugfs_fini(priv);
	return -1;
}

/**
 * vga_switcheroo_process_delayed_switch() - helper for delayed switching
 *
 * Process a delayed switch if one is pending. DRM drivers should call this
 * from their ->lastclose callback.
 *
 * Return: 0 on success. -EINVAL if no delayed switch is pending, if the client
 * has unregistered in the meantime or if there are other clients blocking the
 * switch. If the actual switch fails, an error is reported and 0 is returned.
 */
int vga_switcheroo_process_delayed_switch(void)
{
	struct vga_switcheroo_client *client;
	int ret;
	int err = -EINVAL;

	mutex_lock(&vgasr_mutex);
	if (!vgasr_priv.delayed_switch_active)
		goto err;

	pr_info("processing delayed switch to %d\n",
		vgasr_priv.delayed_client_id);

	client = find_client_from_id(&vgasr_priv.clients,
				     vgasr_priv.delayed_client_id);
	if (!client || !check_can_switch())
		goto err;

	ret = vga_switchto_stage2(client);
	if (ret)
		pr_err("delayed switching failed stage 2 %d\n", ret);

	vgasr_priv.delayed_switch_active = false;
	err = 0;
err:
	mutex_unlock(&vgasr_mutex);
	return err;
}
EXPORT_SYMBOL(vga_switcheroo_process_delayed_switch);

/**
 * DOC: Driver power control
 *
 * In this mode of use, the discrete GPU automatically powers up and down at
 * the discretion of the driver's runtime pm. On muxed machines, the user may
 * still influence the muxer state by way of the debugfs interface, however
 * the ON and OFF commands become a no-op for the discrete GPU.
 *
 * This mode is the default on Nvidia HybridPower/Optimus and ATI PowerXpress.
 * Specifying nouveau.runpm=0, radeon.runpm=0 or amdgpu.runpm=0 on the kernel
 * command line disables it.
 *
 * When the driver decides to power up or down, it notifies vga_switcheroo
 * thereof so that it can (a) power the audio device on the GPU up or down,
 * and (b) update its internal power state representation for the device.
 * This is achieved by vga_switcheroo_set_dynamic_switch().
 *
 * After the GPU has been suspended, the handler needs to be called to cut
 * power to the GPU. Likewise it needs to reinstate power before the GPU
 * can resume. This is achieved by vga_switcheroo_init_domain_pm_ops(),
 * which augments the GPU's suspend/resume functions by the requisite
 * calls to the handler.
 *
 * When the audio device resumes, the GPU needs to be woken. This is achieved
 * by vga_switcheroo_init_domain_pm_optimus_hdmi_audio(), which augments the
 * audio device's resume function.
 *
 * On muxed machines, if the mux is initially switched to the discrete GPU,
 * the user ends up with a black screen when the GPU powers down after boot.
 * As a workaround, the mux is forced to the integrated GPU on runtime suspend,
 * cf. https://bugs.freedesktop.org/show_bug.cgi?id=75917
 */

static void vga_switcheroo_power_switch(struct pci_dev *pdev,
					enum vga_switcheroo_state state)
{
	struct vga_switcheroo_client *client;

	if (!vgasr_priv.handler->power_state)
		return;

	client = find_client_from_pci(&vgasr_priv.clients, pdev);
	if (!client)
		return;

	if (!client->driver_power_control)
		return;

	vgasr_priv.handler->power_state(client->id, state);
}

/**
 * vga_switcheroo_set_dynamic_switch() - helper for driver power control
 * @pdev: client pci device
 * @dynamic: new power state
 *
 * Helper for GPUs whose power state is controlled by the driver's runtime pm.
 * When the driver decides to power up or down, it notifies vga_switcheroo
 * thereof using this helper so that it can (a) power the audio device on
 * the GPU up or down, and (b) update its internal power state representation
 * for the device.
 */
void vga_switcheroo_set_dynamic_switch(struct pci_dev *pdev,
				       enum vga_switcheroo_state dynamic)
{
	struct vga_switcheroo_client *client;

	mutex_lock(&vgasr_mutex);
	client = find_client_from_pci(&vgasr_priv.clients, pdev);
	if (!client || !client->driver_power_control) {
		mutex_unlock(&vgasr_mutex);
		return;
	}

	client->pwr_state = dynamic;
	set_audio_state(client->id, dynamic);
	mutex_unlock(&vgasr_mutex);
}
EXPORT_SYMBOL(vga_switcheroo_set_dynamic_switch);

/* switcheroo power domain */
static int vga_switcheroo_runtime_suspend(struct device *dev)
{
	struct pci_dev *pdev = to_pci_dev(dev);
	int ret;

	ret = dev->bus->pm->runtime_suspend(dev);
	if (ret)
		return ret;
	mutex_lock(&vgasr_mutex);
	if (vgasr_priv.handler->switchto)
		vgasr_priv.handler->switchto(VGA_SWITCHEROO_IGD);
	vga_switcheroo_power_switch(pdev, VGA_SWITCHEROO_OFF);
	mutex_unlock(&vgasr_mutex);
	return 0;
}

static int vga_switcheroo_runtime_resume(struct device *dev)
{
	struct pci_dev *pdev = to_pci_dev(dev);
	int ret;

	mutex_lock(&vgasr_mutex);
	vga_switcheroo_power_switch(pdev, VGA_SWITCHEROO_ON);
	mutex_unlock(&vgasr_mutex);
	ret = dev->bus->pm->runtime_resume(dev);
	if (ret)
		return ret;

	return 0;
}

/**
 * vga_switcheroo_init_domain_pm_ops() - helper for driver power control
 * @dev: vga client device
 * @domain: power domain
 *
 * Helper for GPUs whose power state is controlled by the driver's runtime pm.
 * After the GPU has been suspended, the handler needs to be called to cut
 * power to the GPU. Likewise it needs to reinstate power before the GPU
 * can resume. To this end, this helper augments the suspend/resume functions
 * by the requisite calls to the handler. It needs only be called on platforms
 * where the power switch is separate to the device being powered down.
 */
int vga_switcheroo_init_domain_pm_ops(struct device *dev,
				      struct dev_pm_domain *domain)
{
	/* copy over all the bus versions */
	if (dev->bus && dev->bus->pm) {
		domain->ops = *dev->bus->pm;
		domain->ops.runtime_suspend = vga_switcheroo_runtime_suspend;
		domain->ops.runtime_resume = vga_switcheroo_runtime_resume;

		dev->pm_domain = domain;
		return 0;
	}
	dev->pm_domain = NULL;
	return -EINVAL;
}
EXPORT_SYMBOL(vga_switcheroo_init_domain_pm_ops);

void vga_switcheroo_fini_domain_pm_ops(struct device *dev)
{
	dev->pm_domain = NULL;
}
EXPORT_SYMBOL(vga_switcheroo_fini_domain_pm_ops);

static int vga_switcheroo_runtime_resume_hdmi_audio(struct device *dev)
{
	struct pci_dev *pdev = to_pci_dev(dev);
	struct vga_switcheroo_client *client;
	struct device *video_dev = NULL;
	int ret;

	/* we need to check if we have to switch back on the video
	   device so the audio device can come back */
	mutex_lock(&vgasr_mutex);
	list_for_each_entry(client, &vgasr_priv.clients, list) {
		if (PCI_SLOT(client->pdev->devfn) == PCI_SLOT(pdev->devfn) &&
		    client_is_vga(client)) {
			video_dev = &client->pdev->dev;
			break;
		}
	}
	mutex_unlock(&vgasr_mutex);

	if (video_dev) {
		ret = pm_runtime_get_sync(video_dev);
		if (ret && ret != 1)
			return ret;
	}
	ret = dev->bus->pm->runtime_resume(dev);

	/* put the reference for the gpu */
	if (video_dev) {
		pm_runtime_mark_last_busy(video_dev);
		pm_runtime_put_autosuspend(video_dev);
	}
	return ret;
}

/**
 * vga_switcheroo_init_domain_pm_optimus_hdmi_audio() - helper for driver
 * 	power control
 * @dev: audio client device
 * @domain: power domain
 *
 * Helper for GPUs whose power state is controlled by the driver's runtime pm.
 * When the audio device resumes, the GPU needs to be woken. This helper
 * augments the audio device's resume function to do that.
 *
 * Return: 0 on success, -EINVAL if no power management operations are
 * defined for this device.
 */
int
vga_switcheroo_init_domain_pm_optimus_hdmi_audio(struct device *dev,
						 struct dev_pm_domain *domain)
{
	/* copy over all the bus versions */
	if (dev->bus && dev->bus->pm) {
		domain->ops = *dev->bus->pm;
		domain->ops.runtime_resume =
			vga_switcheroo_runtime_resume_hdmi_audio;

		dev->pm_domain = domain;
		return 0;
	}
	dev->pm_domain = NULL;
	return -EINVAL;
}
EXPORT_SYMBOL(vga_switcheroo_init_domain_pm_optimus_hdmi_audio);