summaryrefslogtreecommitdiff
path: root/drivers/platform/x86/apple-gmux.c
blob: 9aae45a452002cf842d9c5fb100010a2f843a6df (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
// SPDX-License-Identifier: GPL-2.0-only
/*
 *  Gmux driver for Apple laptops
 *
 *  Copyright (C) Canonical Ltd. <seth.forshee@canonical.com>
 *  Copyright (C) 2010-2012 Andreas Heider <andreas@meetr.de>
 *  Copyright (C) 2015 Lukas Wunner <lukas@wunner.de>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/backlight.h>
#include <linux/acpi.h>
#include <linux/pnp.h>
#include <linux/apple_bl.h>
#include <linux/apple-gmux.h>
#include <linux/slab.h>
#include <linux/delay.h>
#include <linux/pci.h>
#include <linux/vga_switcheroo.h>
#include <acpi/video.h>
#include <asm/io.h>

/**
 * DOC: Overview
 *
 * gmux is a microcontroller built into the MacBook Pro to support dual GPUs:
 * A `Lattice XP2`_ on pre-retinas, a `Renesas R4F2113`_ on retinas.
 *
 * (The MacPro6,1 2013 also has a gmux, however it is unclear why since it has
 * dual GPUs but no built-in display.)
 *
 * gmux is connected to the LPC bus of the southbridge. Its I/O ports are
 * accessed differently depending on the microcontroller: Driver functions
 * to access a pre-retina gmux are infixed ``_pio_``, those for a retina gmux
 * are infixed ``_index_``.
 *
 * .. _Lattice XP2:
 *     http://www.latticesemi.com/en/Products/FPGAandCPLD/LatticeXP2.aspx
 * .. _Renesas R4F2113:
 *     http://www.renesas.com/products/mpumcu/h8s/h8s2100/h8s2113/index.jsp
 */

struct apple_gmux_data {
	unsigned long iostart;
	unsigned long iolen;
	bool indexed;
	struct mutex index_lock;

	struct backlight_device *bdev;

	/* switcheroo data */
	acpi_handle dhandle;
	int gpe;
	bool external_switchable;
	enum vga_switcheroo_client_id switch_state_display;
	enum vga_switcheroo_client_id switch_state_ddc;
	enum vga_switcheroo_client_id switch_state_external;
	enum vga_switcheroo_state power_state;
	struct completion powerchange_done;
};

static struct apple_gmux_data *apple_gmux_data;

/*
 * gmux port offsets. Many of these are not yet used, but may be in the
 * future, and it's useful to have them documented here anyhow.
 */
#define GMUX_PORT_VERSION_MAJOR		0x04
#define GMUX_PORT_VERSION_MINOR		0x05
#define GMUX_PORT_VERSION_RELEASE	0x06
#define GMUX_PORT_SWITCH_DISPLAY	0x10
#define GMUX_PORT_SWITCH_GET_DISPLAY	0x11
#define GMUX_PORT_INTERRUPT_ENABLE	0x14
#define GMUX_PORT_INTERRUPT_STATUS	0x16
#define GMUX_PORT_SWITCH_DDC		0x28
#define GMUX_PORT_SWITCH_EXTERNAL	0x40
#define GMUX_PORT_SWITCH_GET_EXTERNAL	0x41
#define GMUX_PORT_DISCRETE_POWER	0x50
#define GMUX_PORT_MAX_BRIGHTNESS	0x70
#define GMUX_PORT_BRIGHTNESS		0x74
#define GMUX_PORT_VALUE			0xc2
#define GMUX_PORT_READ			0xd0
#define GMUX_PORT_WRITE			0xd4

#define GMUX_MIN_IO_LEN			(GMUX_PORT_BRIGHTNESS + 4)

#define GMUX_INTERRUPT_ENABLE		0xff
#define GMUX_INTERRUPT_DISABLE		0x00

#define GMUX_INTERRUPT_STATUS_ACTIVE	0
#define GMUX_INTERRUPT_STATUS_DISPLAY	(1 << 0)
#define GMUX_INTERRUPT_STATUS_POWER	(1 << 2)
#define GMUX_INTERRUPT_STATUS_HOTPLUG	(1 << 3)

#define GMUX_BRIGHTNESS_MASK		0x00ffffff
#define GMUX_MAX_BRIGHTNESS		GMUX_BRIGHTNESS_MASK

static u8 gmux_pio_read8(struct apple_gmux_data *gmux_data, int port)
{
	return inb(gmux_data->iostart + port);
}

static void gmux_pio_write8(struct apple_gmux_data *gmux_data, int port,
			       u8 val)
{
	outb(val, gmux_data->iostart + port);
}

static u32 gmux_pio_read32(struct apple_gmux_data *gmux_data, int port)
{
	return inl(gmux_data->iostart + port);
}

static void gmux_pio_write32(struct apple_gmux_data *gmux_data, int port,
			     u32 val)
{
	int i;
	u8 tmpval;

	for (i = 0; i < 4; i++) {
		tmpval = (val >> (i * 8)) & 0xff;
		outb(tmpval, gmux_data->iostart + port + i);
	}
}

static int gmux_index_wait_ready(struct apple_gmux_data *gmux_data)
{
	int i = 200;
	u8 gwr = inb(gmux_data->iostart + GMUX_PORT_WRITE);

	while (i && (gwr & 0x01)) {
		inb(gmux_data->iostart + GMUX_PORT_READ);
		gwr = inb(gmux_data->iostart + GMUX_PORT_WRITE);
		udelay(100);
		i--;
	}

	return !!i;
}

static int gmux_index_wait_complete(struct apple_gmux_data *gmux_data)
{
	int i = 200;
	u8 gwr = inb(gmux_data->iostart + GMUX_PORT_WRITE);

	while (i && !(gwr & 0x01)) {
		gwr = inb(gmux_data->iostart + GMUX_PORT_WRITE);
		udelay(100);
		i--;
	}

	if (gwr & 0x01)
		inb(gmux_data->iostart + GMUX_PORT_READ);

	return !!i;
}

static u8 gmux_index_read8(struct apple_gmux_data *gmux_data, int port)
{
	u8 val;

	mutex_lock(&gmux_data->index_lock);
	gmux_index_wait_ready(gmux_data);
	outb((port & 0xff), gmux_data->iostart + GMUX_PORT_READ);
	gmux_index_wait_complete(gmux_data);
	val = inb(gmux_data->iostart + GMUX_PORT_VALUE);
	mutex_unlock(&gmux_data->index_lock);

	return val;
}

static void gmux_index_write8(struct apple_gmux_data *gmux_data, int port,
			      u8 val)
{
	mutex_lock(&gmux_data->index_lock);
	outb(val, gmux_data->iostart + GMUX_PORT_VALUE);
	gmux_index_wait_ready(gmux_data);
	outb(port & 0xff, gmux_data->iostart + GMUX_PORT_WRITE);
	gmux_index_wait_complete(gmux_data);
	mutex_unlock(&gmux_data->index_lock);
}

static u32 gmux_index_read32(struct apple_gmux_data *gmux_data, int port)
{
	u32 val;

	mutex_lock(&gmux_data->index_lock);
	gmux_index_wait_ready(gmux_data);
	outb((port & 0xff), gmux_data->iostart + GMUX_PORT_READ);
	gmux_index_wait_complete(gmux_data);
	val = inl(gmux_data->iostart + GMUX_PORT_VALUE);
	mutex_unlock(&gmux_data->index_lock);

	return val;
}

static void gmux_index_write32(struct apple_gmux_data *gmux_data, int port,
			       u32 val)
{
	int i;
	u8 tmpval;

	mutex_lock(&gmux_data->index_lock);

	for (i = 0; i < 4; i++) {
		tmpval = (val >> (i * 8)) & 0xff;
		outb(tmpval, gmux_data->iostart + GMUX_PORT_VALUE + i);
	}

	gmux_index_wait_ready(gmux_data);
	outb(port & 0xff, gmux_data->iostart + GMUX_PORT_WRITE);
	gmux_index_wait_complete(gmux_data);
	mutex_unlock(&gmux_data->index_lock);
}

static u8 gmux_read8(struct apple_gmux_data *gmux_data, int port)
{
	if (gmux_data->indexed)
		return gmux_index_read8(gmux_data, port);
	else
		return gmux_pio_read8(gmux_data, port);
}

static void gmux_write8(struct apple_gmux_data *gmux_data, int port, u8 val)
{
	if (gmux_data->indexed)
		gmux_index_write8(gmux_data, port, val);
	else
		gmux_pio_write8(gmux_data, port, val);
}

static u32 gmux_read32(struct apple_gmux_data *gmux_data, int port)
{
	if (gmux_data->indexed)
		return gmux_index_read32(gmux_data, port);
	else
		return gmux_pio_read32(gmux_data, port);
}

static void gmux_write32(struct apple_gmux_data *gmux_data, int port,
			     u32 val)
{
	if (gmux_data->indexed)
		gmux_index_write32(gmux_data, port, val);
	else
		gmux_pio_write32(gmux_data, port, val);
}

static bool gmux_is_indexed(struct apple_gmux_data *gmux_data)
{
	u16 val;

	outb(0xaa, gmux_data->iostart + 0xcc);
	outb(0x55, gmux_data->iostart + 0xcd);
	outb(0x00, gmux_data->iostart + 0xce);

	val = inb(gmux_data->iostart + 0xcc) |
		(inb(gmux_data->iostart + 0xcd) << 8);

	if (val == 0x55aa)
		return true;

	return false;
}

/**
 * DOC: Backlight control
 *
 * On single GPU MacBooks, the PWM signal for the backlight is generated by
 * the GPU. On dual GPU MacBook Pros by contrast, either GPU may be suspended
 * to conserve energy. Hence the PWM signal needs to be generated by a separate
 * backlight driver which is controlled by gmux. The earliest generation
 * MBP5 2008/09 uses a `TI LP8543`_ backlight driver. All newer models
 * use a `TI LP8545`_.
 *
 * .. _TI LP8543: https://www.ti.com/lit/ds/symlink/lp8543.pdf
 * .. _TI LP8545: https://www.ti.com/lit/ds/symlink/lp8545.pdf
 */

static int gmux_get_brightness(struct backlight_device *bd)
{
	struct apple_gmux_data *gmux_data = bl_get_data(bd);
	return gmux_read32(gmux_data, GMUX_PORT_BRIGHTNESS) &
	       GMUX_BRIGHTNESS_MASK;
}

static int gmux_update_status(struct backlight_device *bd)
{
	struct apple_gmux_data *gmux_data = bl_get_data(bd);
	u32 brightness = bd->props.brightness;

	if (bd->props.state & BL_CORE_SUSPENDED)
		return 0;

	gmux_write32(gmux_data, GMUX_PORT_BRIGHTNESS, brightness);

	return 0;
}

static const struct backlight_ops gmux_bl_ops = {
	.options = BL_CORE_SUSPENDRESUME,
	.get_brightness = gmux_get_brightness,
	.update_status = gmux_update_status,
};

/**
 * DOC: Graphics mux
 *
 * On pre-retinas, the LVDS outputs of both GPUs feed into gmux which muxes
 * either of them to the panel. One of the tricks gmux has up its sleeve is
 * to lengthen the blanking interval of its output during a switch to
 * synchronize it with the GPU switched to. This allows for a flicker-free
 * switch that is imperceptible by the user (`US 8,687,007 B2`_).
 *
 * On retinas, muxing is no longer done by gmux itself, but by a separate
 * chip which is controlled by gmux. The chip is triple sourced, it is
 * either an `NXP CBTL06142`_, `TI HD3SS212`_ or `Pericom PI3VDP12412`_.
 * The panel is driven with eDP instead of LVDS since the pixel clock
 * required for retina resolution exceeds LVDS' limits.
 *
 * Pre-retinas are able to switch the panel's DDC pins separately.
 * This is handled by a `TI SN74LV4066A`_ which is controlled by gmux.
 * The inactive GPU can thus probe the panel's EDID without switching over
 * the entire panel. Retinas lack this functionality as the chips used for
 * eDP muxing are incapable of switching the AUX channel separately (see
 * the linked data sheets, Pericom would be capable but this is unused).
 * However the retina panel has the NO_AUX_HANDSHAKE_LINK_TRAINING bit set
 * in its DPCD, allowing the inactive GPU to skip the AUX handshake and
 * set up the output with link parameters pre-calibrated by the active GPU.
 *
 * The external DP port is only fully switchable on the first two unibody
 * MacBook Pro generations, MBP5 2008/09 and MBP6 2010. This is done by an
 * `NXP CBTL06141`_ which is controlled by gmux. It's the predecessor of the
 * eDP mux on retinas, the difference being support for 2.7 versus 5.4 Gbit/s.
 *
 * The following MacBook Pro generations replaced the external DP port with a
 * combined DP/Thunderbolt port and lost the ability to switch it between GPUs,
 * connecting it either to the discrete GPU or the Thunderbolt controller.
 * Oddly enough, while the full port is no longer switchable, AUX and HPD
 * are still switchable by way of an `NXP CBTL03062`_ (on pre-retinas
 * MBP8 2011 and MBP9 2012) or two `TI TS3DS10224`_ (on retinas) under the
 * control of gmux. Since the integrated GPU is missing the main link,
 * external displays appear to it as phantoms which fail to link-train.
 *
 * gmux receives the HPD signal of all display connectors and sends an
 * interrupt on hotplug. On generations which cannot switch external ports,
 * the discrete GPU can then be woken to drive the newly connected display.
 * The ability to switch AUX on these generations could be used to improve
 * reliability of hotplug detection by having the integrated GPU poll the
 * ports while the discrete GPU is asleep, but currently we do not make use
 * of this feature.
 *
 * Our switching policy for the external port is that on those generations
 * which are able to switch it fully, the port is switched together with the
 * panel when IGD / DIS commands are issued to vga_switcheroo. It is thus
 * possible to drive e.g. a beamer on battery power with the integrated GPU.
 * The user may manually switch to the discrete GPU if more performance is
 * needed.
 *
 * On all newer generations, the external port can only be driven by the
 * discrete GPU. If a display is plugged in while the panel is switched to
 * the integrated GPU, *both* GPUs will be in use for maximum performance.
 * To decrease power consumption, the user may manually switch to the
 * discrete GPU, thereby suspending the integrated GPU.
 *
 * gmux' initial switch state on bootup is user configurable via the EFI
 * variable ``gpu-power-prefs-fa4ce28d-b62f-4c99-9cc3-6815686e30f9`` (5th byte,
 * 1 = IGD, 0 = DIS). Based on this setting, the EFI firmware tells gmux to
 * switch the panel and the external DP connector and allocates a framebuffer
 * for the selected GPU.
 *
 * .. _US 8,687,007 B2: https://pimg-fpiw.uspto.gov/fdd/07/870/086/0.pdf
 * .. _NXP CBTL06141:   https://www.nxp.com/documents/data_sheet/CBTL06141.pdf
 * .. _NXP CBTL06142:   https://www.nxp.com/documents/data_sheet/CBTL06141.pdf
 * .. _TI HD3SS212:     https://www.ti.com/lit/ds/symlink/hd3ss212.pdf
 * .. _Pericom PI3VDP12412: https://www.pericom.com/assets/Datasheets/PI3VDP12412.pdf
 * .. _TI SN74LV4066A:  https://www.ti.com/lit/ds/symlink/sn74lv4066a.pdf
 * .. _NXP CBTL03062:   http://pdf.datasheetarchive.com/indexerfiles/Datasheets-SW16/DSASW00308511.pdf
 * .. _TI TS3DS10224:   https://www.ti.com/lit/ds/symlink/ts3ds10224.pdf
 */

static void gmux_read_switch_state(struct apple_gmux_data *gmux_data)
{
	if (gmux_read8(gmux_data, GMUX_PORT_SWITCH_DDC) == 1)
		gmux_data->switch_state_ddc = VGA_SWITCHEROO_IGD;
	else
		gmux_data->switch_state_ddc = VGA_SWITCHEROO_DIS;

	if (gmux_read8(gmux_data, GMUX_PORT_SWITCH_DISPLAY) == 2)
		gmux_data->switch_state_display = VGA_SWITCHEROO_IGD;
	else
		gmux_data->switch_state_display = VGA_SWITCHEROO_DIS;

	if (gmux_read8(gmux_data, GMUX_PORT_SWITCH_EXTERNAL) == 2)
		gmux_data->switch_state_external = VGA_SWITCHEROO_IGD;
	else
		gmux_data->switch_state_external = VGA_SWITCHEROO_DIS;
}

static void gmux_write_switch_state(struct apple_gmux_data *gmux_data)
{
	if (gmux_data->switch_state_ddc == VGA_SWITCHEROO_IGD)
		gmux_write8(gmux_data, GMUX_PORT_SWITCH_DDC, 1);
	else
		gmux_write8(gmux_data, GMUX_PORT_SWITCH_DDC, 2);

	if (gmux_data->switch_state_display == VGA_SWITCHEROO_IGD)
		gmux_write8(gmux_data, GMUX_PORT_SWITCH_DISPLAY, 2);
	else
		gmux_write8(gmux_data, GMUX_PORT_SWITCH_DISPLAY, 3);

	if (gmux_data->switch_state_external == VGA_SWITCHEROO_IGD)
		gmux_write8(gmux_data, GMUX_PORT_SWITCH_EXTERNAL, 2);
	else
		gmux_write8(gmux_data, GMUX_PORT_SWITCH_EXTERNAL, 3);
}

static int gmux_switchto(enum vga_switcheroo_client_id id)
{
	apple_gmux_data->switch_state_ddc = id;
	apple_gmux_data->switch_state_display = id;
	if (apple_gmux_data->external_switchable)
		apple_gmux_data->switch_state_external = id;

	gmux_write_switch_state(apple_gmux_data);

	return 0;
}

static int gmux_switch_ddc(enum vga_switcheroo_client_id id)
{
	enum vga_switcheroo_client_id old_ddc_owner =
		apple_gmux_data->switch_state_ddc;

	if (id == old_ddc_owner)
		return id;

	pr_debug("Switching DDC from %d to %d\n", old_ddc_owner, id);
	apple_gmux_data->switch_state_ddc = id;

	if (id == VGA_SWITCHEROO_IGD)
		gmux_write8(apple_gmux_data, GMUX_PORT_SWITCH_DDC, 1);
	else
		gmux_write8(apple_gmux_data, GMUX_PORT_SWITCH_DDC, 2);

	return old_ddc_owner;
}

/**
 * DOC: Power control
 *
 * gmux is able to cut power to the discrete GPU. It automatically takes care
 * of the correct sequence to tear down and bring up the power rails for
 * core voltage, VRAM and PCIe.
 */

static int gmux_set_discrete_state(struct apple_gmux_data *gmux_data,
				   enum vga_switcheroo_state state)
{
	reinit_completion(&gmux_data->powerchange_done);

	if (state == VGA_SWITCHEROO_ON) {
		gmux_write8(gmux_data, GMUX_PORT_DISCRETE_POWER, 1);
		gmux_write8(gmux_data, GMUX_PORT_DISCRETE_POWER, 3);
		pr_debug("Discrete card powered up\n");
	} else {
		gmux_write8(gmux_data, GMUX_PORT_DISCRETE_POWER, 1);
		gmux_write8(gmux_data, GMUX_PORT_DISCRETE_POWER, 0);
		pr_debug("Discrete card powered down\n");
	}

	gmux_data->power_state = state;

	if (gmux_data->gpe >= 0 &&
	    !wait_for_completion_interruptible_timeout(&gmux_data->powerchange_done,
						       msecs_to_jiffies(200)))
		pr_warn("Timeout waiting for gmux switch to complete\n");

	return 0;
}

static int gmux_set_power_state(enum vga_switcheroo_client_id id,
				enum vga_switcheroo_state state)
{
	if (id == VGA_SWITCHEROO_IGD)
		return 0;

	return gmux_set_discrete_state(apple_gmux_data, state);
}

static enum vga_switcheroo_client_id gmux_get_client_id(struct pci_dev *pdev)
{
	/*
	 * Early Macbook Pros with switchable graphics use nvidia
	 * integrated graphics. Hardcode that the 9400M is integrated.
	 */
	if (pdev->vendor == PCI_VENDOR_ID_INTEL)
		return VGA_SWITCHEROO_IGD;
	else if (pdev->vendor == PCI_VENDOR_ID_NVIDIA &&
		 pdev->device == 0x0863)
		return VGA_SWITCHEROO_IGD;
	else
		return VGA_SWITCHEROO_DIS;
}

static const struct vga_switcheroo_handler gmux_handler_indexed = {
	.switchto = gmux_switchto,
	.power_state = gmux_set_power_state,
	.get_client_id = gmux_get_client_id,
};

static const struct vga_switcheroo_handler gmux_handler_classic = {
	.switchto = gmux_switchto,
	.switch_ddc = gmux_switch_ddc,
	.power_state = gmux_set_power_state,
	.get_client_id = gmux_get_client_id,
};

/**
 * DOC: Interrupt
 *
 * gmux is also connected to a GPIO pin of the southbridge and thereby is able
 * to trigger an ACPI GPE. On the MBP5 2008/09 it's GPIO pin 22 of the Nvidia
 * MCP79, on all following generations it's GPIO pin 6 of the Intel PCH.
 * The GPE merely signals that an interrupt occurred, the actual type of event
 * is identified by reading a gmux register.
 */

static inline void gmux_disable_interrupts(struct apple_gmux_data *gmux_data)
{
	gmux_write8(gmux_data, GMUX_PORT_INTERRUPT_ENABLE,
		    GMUX_INTERRUPT_DISABLE);
}

static inline void gmux_enable_interrupts(struct apple_gmux_data *gmux_data)
{
	gmux_write8(gmux_data, GMUX_PORT_INTERRUPT_ENABLE,
		    GMUX_INTERRUPT_ENABLE);
}

static inline u8 gmux_interrupt_get_status(struct apple_gmux_data *gmux_data)
{
	return gmux_read8(gmux_data, GMUX_PORT_INTERRUPT_STATUS);
}

static void gmux_clear_interrupts(struct apple_gmux_data *gmux_data)
{
	u8 status;

	/* to clear interrupts write back current status */
	status = gmux_interrupt_get_status(gmux_data);
	gmux_write8(gmux_data, GMUX_PORT_INTERRUPT_STATUS, status);
}

static void gmux_notify_handler(acpi_handle device, u32 value, void *context)
{
	u8 status;
	struct pnp_dev *pnp = (struct pnp_dev *)context;
	struct apple_gmux_data *gmux_data = pnp_get_drvdata(pnp);

	status = gmux_interrupt_get_status(gmux_data);
	gmux_disable_interrupts(gmux_data);
	pr_debug("Notify handler called: status %d\n", status);

	gmux_clear_interrupts(gmux_data);
	gmux_enable_interrupts(gmux_data);

	if (status & GMUX_INTERRUPT_STATUS_POWER)
		complete(&gmux_data->powerchange_done);
}

static int gmux_suspend(struct device *dev)
{
	struct pnp_dev *pnp = to_pnp_dev(dev);
	struct apple_gmux_data *gmux_data = pnp_get_drvdata(pnp);

	gmux_disable_interrupts(gmux_data);
	return 0;
}

static int gmux_resume(struct device *dev)
{
	struct pnp_dev *pnp = to_pnp_dev(dev);
	struct apple_gmux_data *gmux_data = pnp_get_drvdata(pnp);

	gmux_enable_interrupts(gmux_data);
	gmux_write_switch_state(gmux_data);
	if (gmux_data->power_state == VGA_SWITCHEROO_OFF)
		gmux_set_discrete_state(gmux_data, gmux_data->power_state);
	return 0;
}

static int is_thunderbolt(struct device *dev, void *data)
{
	return to_pci_dev(dev)->is_thunderbolt;
}

static int gmux_probe(struct pnp_dev *pnp, const struct pnp_device_id *id)
{
	struct apple_gmux_data *gmux_data;
	struct resource *res;
	struct backlight_properties props;
	struct backlight_device *bdev;
	u8 ver_major, ver_minor, ver_release;
	int ret = -ENXIO;
	acpi_status status;
	unsigned long long gpe;

	if (apple_gmux_data)
		return -EBUSY;

	gmux_data = kzalloc(sizeof(*gmux_data), GFP_KERNEL);
	if (!gmux_data)
		return -ENOMEM;
	pnp_set_drvdata(pnp, gmux_data);

	res = pnp_get_resource(pnp, IORESOURCE_IO, 0);
	if (!res) {
		pr_err("Failed to find gmux I/O resource\n");
		goto err_free;
	}

	gmux_data->iostart = res->start;
	gmux_data->iolen = res->end - res->start;

	if (gmux_data->iolen < GMUX_MIN_IO_LEN) {
		pr_err("gmux I/O region too small (%lu < %u)\n",
		       gmux_data->iolen, GMUX_MIN_IO_LEN);
		goto err_free;
	}

	if (!request_region(gmux_data->iostart, gmux_data->iolen,
			    "Apple gmux")) {
		pr_err("gmux I/O already in use\n");
		goto err_free;
	}

	/*
	 * Invalid version information may indicate either that the gmux
	 * device isn't present or that it's a new one that uses indexed
	 * io
	 */

	ver_major = gmux_read8(gmux_data, GMUX_PORT_VERSION_MAJOR);
	ver_minor = gmux_read8(gmux_data, GMUX_PORT_VERSION_MINOR);
	ver_release = gmux_read8(gmux_data, GMUX_PORT_VERSION_RELEASE);
	if (ver_major == 0xff && ver_minor == 0xff && ver_release == 0xff) {
		if (gmux_is_indexed(gmux_data)) {
			u32 version;
			mutex_init(&gmux_data->index_lock);
			gmux_data->indexed = true;
			version = gmux_read32(gmux_data,
				GMUX_PORT_VERSION_MAJOR);
			ver_major = (version >> 24) & 0xff;
			ver_minor = (version >> 16) & 0xff;
			ver_release = (version >> 8) & 0xff;
		} else {
			pr_info("gmux device not present\n");
			ret = -ENODEV;
			goto err_release;
		}
	}
	pr_info("Found gmux version %d.%d.%d [%s]\n", ver_major, ver_minor,
		ver_release, (gmux_data->indexed ? "indexed" : "classic"));

	memset(&props, 0, sizeof(props));
	props.type = BACKLIGHT_PLATFORM;
	props.max_brightness = gmux_read32(gmux_data, GMUX_PORT_MAX_BRIGHTNESS);

	/*
	 * Currently it's assumed that the maximum brightness is less than
	 * 2^24 for compatibility with old gmux versions. Cap the max
	 * brightness at this value, but print a warning if the hardware
	 * reports something higher so that it can be fixed.
	 */
	if (WARN_ON(props.max_brightness > GMUX_MAX_BRIGHTNESS))
		props.max_brightness = GMUX_MAX_BRIGHTNESS;

	bdev = backlight_device_register("gmux_backlight", &pnp->dev,
					 gmux_data, &gmux_bl_ops, &props);
	if (IS_ERR(bdev)) {
		ret = PTR_ERR(bdev);
		goto err_release;
	}

	gmux_data->bdev = bdev;
	bdev->props.brightness = gmux_get_brightness(bdev);
	backlight_update_status(bdev);

	/*
	 * The backlight situation on Macs is complicated. If the gmux is
	 * present it's the best choice, because it always works for
	 * backlight control and supports more levels than other options.
	 * Disable the other backlight choices.
	 */
	acpi_video_set_dmi_backlight_type(acpi_backlight_vendor);
	apple_bl_unregister();

	gmux_data->power_state = VGA_SWITCHEROO_ON;

	gmux_data->dhandle = ACPI_HANDLE(&pnp->dev);
	if (!gmux_data->dhandle) {
		pr_err("Cannot find acpi handle for pnp device %s\n",
		       dev_name(&pnp->dev));
		ret = -ENODEV;
		goto err_notify;
	}

	status = acpi_evaluate_integer(gmux_data->dhandle, "GMGP", NULL, &gpe);
	if (ACPI_SUCCESS(status)) {
		gmux_data->gpe = (int)gpe;

		status = acpi_install_notify_handler(gmux_data->dhandle,
						     ACPI_DEVICE_NOTIFY,
						     &gmux_notify_handler, pnp);
		if (ACPI_FAILURE(status)) {
			pr_err("Install notify handler failed: %s\n",
			       acpi_format_exception(status));
			ret = -ENODEV;
			goto err_notify;
		}

		status = acpi_enable_gpe(NULL, gmux_data->gpe);
		if (ACPI_FAILURE(status)) {
			pr_err("Cannot enable gpe: %s\n",
			       acpi_format_exception(status));
			goto err_enable_gpe;
		}
	} else {
		pr_warn("No GPE found for gmux\n");
		gmux_data->gpe = -1;
	}

	/*
	 * If Thunderbolt is present, the external DP port is not fully
	 * switchable. Force its AUX channel to the discrete GPU.
	 */
	gmux_data->external_switchable =
		!bus_for_each_dev(&pci_bus_type, NULL, NULL, is_thunderbolt);
	if (!gmux_data->external_switchable)
		gmux_write8(gmux_data, GMUX_PORT_SWITCH_EXTERNAL, 3);

	apple_gmux_data = gmux_data;
	init_completion(&gmux_data->powerchange_done);
	gmux_enable_interrupts(gmux_data);
	gmux_read_switch_state(gmux_data);

	/*
	 * Retina MacBook Pros cannot switch the panel's AUX separately
	 * and need eDP pre-calibration. They are distinguishable from
	 * pre-retinas by having an "indexed" gmux.
	 *
	 * Pre-retina MacBook Pros can switch the panel's DDC separately.
	 */
	if (gmux_data->indexed)
		ret = vga_switcheroo_register_handler(&gmux_handler_indexed,
					      VGA_SWITCHEROO_NEEDS_EDP_CONFIG);
	else
		ret = vga_switcheroo_register_handler(&gmux_handler_classic,
					      VGA_SWITCHEROO_CAN_SWITCH_DDC);
	if (ret) {
		pr_err("Failed to register vga_switcheroo handler\n");
		goto err_register_handler;
	}

	return 0;

err_register_handler:
	gmux_disable_interrupts(gmux_data);
	apple_gmux_data = NULL;
	if (gmux_data->gpe >= 0)
		acpi_disable_gpe(NULL, gmux_data->gpe);
err_enable_gpe:
	if (gmux_data->gpe >= 0)
		acpi_remove_notify_handler(gmux_data->dhandle,
					   ACPI_DEVICE_NOTIFY,
					   &gmux_notify_handler);
err_notify:
	backlight_device_unregister(bdev);
err_release:
	release_region(gmux_data->iostart, gmux_data->iolen);
err_free:
	kfree(gmux_data);
	return ret;
}

static void gmux_remove(struct pnp_dev *pnp)
{
	struct apple_gmux_data *gmux_data = pnp_get_drvdata(pnp);

	vga_switcheroo_unregister_handler();
	gmux_disable_interrupts(gmux_data);
	if (gmux_data->gpe >= 0) {
		acpi_disable_gpe(NULL, gmux_data->gpe);
		acpi_remove_notify_handler(gmux_data->dhandle,
					   ACPI_DEVICE_NOTIFY,
					   &gmux_notify_handler);
	}

	backlight_device_unregister(gmux_data->bdev);

	release_region(gmux_data->iostart, gmux_data->iolen);
	apple_gmux_data = NULL;
	kfree(gmux_data);

	acpi_video_register();
	apple_bl_register();
}

static const struct pnp_device_id gmux_device_ids[] = {
	{GMUX_ACPI_HID, 0},
	{"", 0}
};

static const struct dev_pm_ops gmux_dev_pm_ops = {
	.suspend = gmux_suspend,
	.resume = gmux_resume,
};

static struct pnp_driver gmux_pnp_driver = {
	.name		= "apple-gmux",
	.probe		= gmux_probe,
	.remove		= gmux_remove,
	.id_table	= gmux_device_ids,
	.driver		= {
			.pm = &gmux_dev_pm_ops,
	},
};

module_pnp_driver(gmux_pnp_driver);
MODULE_AUTHOR("Seth Forshee <seth.forshee@canonical.com>");
MODULE_DESCRIPTION("Apple Gmux Driver");
MODULE_LICENSE("GPL");
MODULE_DEVICE_TABLE(pnp, gmux_device_ids);