Training courses

Kernel and Embedded Linux

Bootlin training courses

Embedded Linux, kernel,
Yocto Project, Buildroot, real-time,
graphics, boot time, debugging...

Bootlin logo

Elixir Cross Referencer

  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
/*
 * Copyright © 2015 Intel Corporation
 *
 * 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.
 */

#include <linux/kernel.h>

#include <drm/i915_drm.h>

#include "i915_drv.h"
#include "intel_display_types.h"
#include "intel_hotplug.h"

/**
 * DOC: Hotplug
 *
 * Simply put, hotplug occurs when a display is connected to or disconnected
 * from the system. However, there may be adapters and docking stations and
 * Display Port short pulses and MST devices involved, complicating matters.
 *
 * Hotplug in i915 is handled in many different levels of abstraction.
 *
 * The platform dependent interrupt handling code in i915_irq.c enables,
 * disables, and does preliminary handling of the interrupts. The interrupt
 * handlers gather the hotplug detect (HPD) information from relevant registers
 * into a platform independent mask of hotplug pins that have fired.
 *
 * The platform independent interrupt handler intel_hpd_irq_handler() in
 * intel_hotplug.c does hotplug irq storm detection and mitigation, and passes
 * further processing to appropriate bottom halves (Display Port specific and
 * regular hotplug).
 *
 * The Display Port work function i915_digport_work_func() calls into
 * intel_dp_hpd_pulse() via hooks, which handles DP short pulses and DP MST long
 * pulses, with failures and non-MST long pulses triggering regular hotplug
 * processing on the connector.
 *
 * The regular hotplug work function i915_hotplug_work_func() calls connector
 * detect hooks, and, if connector status changes, triggers sending of hotplug
 * uevent to userspace via drm_kms_helper_hotplug_event().
 *
 * Finally, the userspace is responsible for triggering a modeset upon receiving
 * the hotplug uevent, disabling or enabling the crtc as needed.
 *
 * The hotplug interrupt storm detection and mitigation code keeps track of the
 * number of interrupts per hotplug pin per a period of time, and if the number
 * of interrupts exceeds a certain threshold, the interrupt is disabled for a
 * while before being re-enabled. The intention is to mitigate issues raising
 * from broken hardware triggering massive amounts of interrupts and grinding
 * the system to a halt.
 *
 * Current implementation expects that hotplug interrupt storm will not be
 * seen when display port sink is connected, hence on platforms whose DP
 * callback is handled by i915_digport_work_func reenabling of hpd is not
 * performed (it was never expected to be disabled in the first place ;) )
 * this is specific to DP sinks handled by this routine and any other display
 * such as HDMI or DVI enabled on the same port will have proper logic since
 * it will use i915_hotplug_work_func where this logic is handled.
 */

/**
 * intel_hpd_pin_default - return default pin associated with certain port.
 * @dev_priv: private driver data pointer
 * @port: the hpd port to get associated pin
 *
 * It is only valid and used by digital port encoder.
 *
 * Return pin that is associatade with @port and HDP_NONE if no pin is
 * hard associated with that @port.
 */
enum hpd_pin intel_hpd_pin_default(struct drm_i915_private *dev_priv,
				   enum port port)
{
	switch (port) {
	case PORT_A:
		return HPD_PORT_A;
	case PORT_B:
		return HPD_PORT_B;
	case PORT_C:
		return HPD_PORT_C;
	case PORT_D:
		return HPD_PORT_D;
	case PORT_E:
		return HPD_PORT_E;
	case PORT_F:
		if (IS_CNL_WITH_PORT_F(dev_priv))
			return HPD_PORT_E;
		return HPD_PORT_F;
	case PORT_G:
		return HPD_PORT_G;
	case PORT_H:
		return HPD_PORT_H;
	case PORT_I:
		return HPD_PORT_I;
	default:
		MISSING_CASE(port);
		return HPD_NONE;
	}
}

#define HPD_STORM_DETECT_PERIOD		1000
#define HPD_STORM_REENABLE_DELAY	(2 * 60 * 1000)
#define HPD_RETRY_DELAY			1000

/**
 * intel_hpd_irq_storm_detect - gather stats and detect HPD IRQ storm on a pin
 * @dev_priv: private driver data pointer
 * @pin: the pin to gather stats on
 * @long_hpd: whether the HPD IRQ was long or short
 *
 * Gather stats about HPD IRQs from the specified @pin, and detect IRQ
 * storms. Only the pin specific stats and state are changed, the caller is
 * responsible for further action.
 *
 * The number of IRQs that are allowed within @HPD_STORM_DETECT_PERIOD is
 * stored in @dev_priv->hotplug.hpd_storm_threshold which defaults to
 * @HPD_STORM_DEFAULT_THRESHOLD. Long IRQs count as +10 to this threshold, and
 * short IRQs count as +1. If this threshold is exceeded, it's considered an
 * IRQ storm and the IRQ state is set to @HPD_MARK_DISABLED.
 *
 * By default, most systems will only count long IRQs towards
 * &dev_priv->hotplug.hpd_storm_threshold. However, some older systems also
 * suffer from short IRQ storms and must also track these. Because short IRQ
 * storms are naturally caused by sideband interactions with DP MST devices,
 * short IRQ detection is only enabled for systems without DP MST support.
 * Systems which are new enough to support DP MST are far less likely to
 * suffer from IRQ storms at all, so this is fine.
 *
 * The HPD threshold can be controlled through i915_hpd_storm_ctl in debugfs,
 * and should only be adjusted for automated hotplug testing.
 *
 * Return true if an IRQ storm was detected on @pin.
 */
static bool intel_hpd_irq_storm_detect(struct drm_i915_private *dev_priv,
				       enum hpd_pin pin, bool long_hpd)
{
	struct i915_hotplug *hpd = &dev_priv->hotplug;
	unsigned long start = hpd->stats[pin].last_jiffies;
	unsigned long end = start + msecs_to_jiffies(HPD_STORM_DETECT_PERIOD);
	const int increment = long_hpd ? 10 : 1;
	const int threshold = hpd->hpd_storm_threshold;
	bool storm = false;

	if (!threshold ||
	    (!long_hpd && !dev_priv->hotplug.hpd_short_storm_enabled))
		return false;

	if (!time_in_range(jiffies, start, end)) {
		hpd->stats[pin].last_jiffies = jiffies;
		hpd->stats[pin].count = 0;
	}

	hpd->stats[pin].count += increment;
	if (hpd->stats[pin].count > threshold) {
		hpd->stats[pin].state = HPD_MARK_DISABLED;
		DRM_DEBUG_KMS("HPD interrupt storm detected on PIN %d\n", pin);
		storm = true;
	} else {
		DRM_DEBUG_KMS("Received HPD interrupt on PIN %d - cnt: %d\n", pin,
			      hpd->stats[pin].count);
	}

	return storm;
}

static void
intel_hpd_irq_storm_switch_to_polling(struct drm_i915_private *dev_priv)
{
	struct drm_device *dev = &dev_priv->drm;
	struct intel_connector *intel_connector;
	struct intel_encoder *intel_encoder;
	struct drm_connector *connector;
	struct drm_connector_list_iter conn_iter;
	enum hpd_pin pin;
	bool hpd_disabled = false;

	lockdep_assert_held(&dev_priv->irq_lock);

	drm_connector_list_iter_begin(dev, &conn_iter);
	drm_for_each_connector_iter(connector, &conn_iter) {
		if (connector->polled != DRM_CONNECTOR_POLL_HPD)
			continue;

		intel_connector = to_intel_connector(connector);
		intel_encoder = intel_connector->encoder;
		if (!intel_encoder)
			continue;

		pin = intel_encoder->hpd_pin;
		if (pin == HPD_NONE ||
		    dev_priv->hotplug.stats[pin].state != HPD_MARK_DISABLED)
			continue;

		DRM_INFO("HPD interrupt storm detected on connector %s: "
			 "switching from hotplug detection to polling\n",
			 connector->name);

		dev_priv->hotplug.stats[pin].state = HPD_DISABLED;
		connector->polled = DRM_CONNECTOR_POLL_CONNECT
			| DRM_CONNECTOR_POLL_DISCONNECT;
		hpd_disabled = true;
	}
	drm_connector_list_iter_end(&conn_iter);

	/* Enable polling and queue hotplug re-enabling. */
	if (hpd_disabled) {
		drm_kms_helper_poll_enable(dev);
		mod_delayed_work(system_wq, &dev_priv->hotplug.reenable_work,
				 msecs_to_jiffies(HPD_STORM_REENABLE_DELAY));
	}
}

static void intel_hpd_irq_storm_reenable_work(struct work_struct *work)
{
	struct drm_i915_private *dev_priv =
		container_of(work, typeof(*dev_priv),
			     hotplug.reenable_work.work);
	struct drm_device *dev = &dev_priv->drm;
	intel_wakeref_t wakeref;
	enum hpd_pin pin;

	wakeref = intel_runtime_pm_get(&dev_priv->runtime_pm);

	spin_lock_irq(&dev_priv->irq_lock);
	for_each_hpd_pin(pin) {
		struct drm_connector *connector;
		struct drm_connector_list_iter conn_iter;

		if (dev_priv->hotplug.stats[pin].state != HPD_DISABLED)
			continue;

		dev_priv->hotplug.stats[pin].state = HPD_ENABLED;

		drm_connector_list_iter_begin(dev, &conn_iter);
		drm_for_each_connector_iter(connector, &conn_iter) {
			struct intel_connector *intel_connector = to_intel_connector(connector);

			/* Don't check MST ports, they don't have pins */
			if (!intel_connector->mst_port &&
			    intel_connector->encoder->hpd_pin == pin) {
				if (connector->polled != intel_connector->polled)
					DRM_DEBUG_DRIVER("Reenabling HPD on connector %s\n",
							 connector->name);
				connector->polled = intel_connector->polled;
				if (!connector->polled)
					connector->polled = DRM_CONNECTOR_POLL_HPD;
			}
		}
		drm_connector_list_iter_end(&conn_iter);
	}
	if (dev_priv->display_irqs_enabled && dev_priv->display.hpd_irq_setup)
		dev_priv->display.hpd_irq_setup(dev_priv);
	spin_unlock_irq(&dev_priv->irq_lock);

	intel_runtime_pm_put(&dev_priv->runtime_pm, wakeref);
}

enum intel_hotplug_state
intel_encoder_hotplug(struct intel_encoder *encoder,
		      struct intel_connector *connector,
		      bool irq_received)
{
	struct drm_device *dev = connector->base.dev;
	enum drm_connector_status old_status;

	WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
	old_status = connector->base.status;

	connector->base.status =
		drm_helper_probe_detect(&connector->base, NULL, false);

	if (old_status == connector->base.status)
		return INTEL_HOTPLUG_UNCHANGED;

	DRM_DEBUG_KMS("[CONNECTOR:%d:%s] status updated from %s to %s\n",
		      connector->base.base.id,
		      connector->base.name,
		      drm_get_connector_status_name(old_status),
		      drm_get_connector_status_name(connector->base.status));

	return INTEL_HOTPLUG_CHANGED;
}

static bool intel_encoder_has_hpd_pulse(struct intel_encoder *encoder)
{
	return intel_encoder_is_dig_port(encoder) &&
		enc_to_dig_port(&encoder->base)->hpd_pulse != NULL;
}

static void i915_digport_work_func(struct work_struct *work)
{
	struct drm_i915_private *dev_priv =
		container_of(work, struct drm_i915_private, hotplug.dig_port_work);
	u32 long_port_mask, short_port_mask;
	struct intel_encoder *encoder;
	u32 old_bits = 0;

	spin_lock_irq(&dev_priv->irq_lock);
	long_port_mask = dev_priv->hotplug.long_port_mask;
	dev_priv->hotplug.long_port_mask = 0;
	short_port_mask = dev_priv->hotplug.short_port_mask;
	dev_priv->hotplug.short_port_mask = 0;
	spin_unlock_irq(&dev_priv->irq_lock);

	for_each_intel_encoder(&dev_priv->drm, encoder) {
		struct intel_digital_port *dig_port;
		enum port port = encoder->port;
		bool long_hpd, short_hpd;
		enum irqreturn ret;

		if (!intel_encoder_has_hpd_pulse(encoder))
			continue;

		long_hpd = long_port_mask & BIT(port);
		short_hpd = short_port_mask & BIT(port);

		if (!long_hpd && !short_hpd)
			continue;

		dig_port = enc_to_dig_port(&encoder->base);

		ret = dig_port->hpd_pulse(dig_port, long_hpd);
		if (ret == IRQ_NONE) {
			/* fall back to old school hpd */
			old_bits |= BIT(encoder->hpd_pin);
		}
	}

	if (old_bits) {
		spin_lock_irq(&dev_priv->irq_lock);
		dev_priv->hotplug.event_bits |= old_bits;
		spin_unlock_irq(&dev_priv->irq_lock);
		queue_delayed_work(system_wq, &dev_priv->hotplug.hotplug_work, 0);
	}
}

/*
 * Handle hotplug events outside the interrupt handler proper.
 */
static void i915_hotplug_work_func(struct work_struct *work)
{
	struct drm_i915_private *dev_priv =
		container_of(work, struct drm_i915_private,
			     hotplug.hotplug_work.work);
	struct drm_device *dev = &dev_priv->drm;
	struct intel_connector *intel_connector;
	struct intel_encoder *intel_encoder;
	struct drm_connector *connector;
	struct drm_connector_list_iter conn_iter;
	u32 changed = 0, retry = 0;
	u32 hpd_event_bits;
	u32 hpd_retry_bits;

	mutex_lock(&dev->mode_config.mutex);
	DRM_DEBUG_KMS("running encoder hotplug functions\n");

	spin_lock_irq(&dev_priv->irq_lock);

	hpd_event_bits = dev_priv->hotplug.event_bits;
	dev_priv->hotplug.event_bits = 0;
	hpd_retry_bits = dev_priv->hotplug.retry_bits;
	dev_priv->hotplug.retry_bits = 0;

	/* Enable polling for connectors which had HPD IRQ storms */
	intel_hpd_irq_storm_switch_to_polling(dev_priv);

	spin_unlock_irq(&dev_priv->irq_lock);

	drm_connector_list_iter_begin(dev, &conn_iter);
	drm_for_each_connector_iter(connector, &conn_iter) {
		u32 hpd_bit;

		intel_connector = to_intel_connector(connector);
		if (!intel_connector->encoder)
			continue;
		intel_encoder = intel_connector->encoder;
		hpd_bit = BIT(intel_encoder->hpd_pin);
		if ((hpd_event_bits | hpd_retry_bits) & hpd_bit) {
			DRM_DEBUG_KMS("Connector %s (pin %i) received hotplug event.\n",
				      connector->name, intel_encoder->hpd_pin);

			switch (intel_encoder->hotplug(intel_encoder,
						       intel_connector,
						       hpd_event_bits & hpd_bit)) {
			case INTEL_HOTPLUG_UNCHANGED:
				break;
			case INTEL_HOTPLUG_CHANGED:
				changed |= hpd_bit;
				break;
			case INTEL_HOTPLUG_RETRY:
				retry |= hpd_bit;
				break;
			}
		}
	}
	drm_connector_list_iter_end(&conn_iter);
	mutex_unlock(&dev->mode_config.mutex);

	if (changed)
		drm_kms_helper_hotplug_event(dev);

	/* Remove shared HPD pins that have changed */
	retry &= ~changed;
	if (retry) {
		spin_lock_irq(&dev_priv->irq_lock);
		dev_priv->hotplug.retry_bits |= retry;
		spin_unlock_irq(&dev_priv->irq_lock);

		mod_delayed_work(system_wq, &dev_priv->hotplug.hotplug_work,
				 msecs_to_jiffies(HPD_RETRY_DELAY));
	}
}


/**
 * intel_hpd_irq_handler - main hotplug irq handler
 * @dev_priv: drm_i915_private
 * @pin_mask: a mask of hpd pins that have triggered the irq
 * @long_mask: a mask of hpd pins that may be long hpd pulses
 *
 * This is the main hotplug irq handler for all platforms. The platform specific
 * irq handlers call the platform specific hotplug irq handlers, which read and
 * decode the appropriate registers into bitmasks about hpd pins that have
 * triggered (@pin_mask), and which of those pins may be long pulses
 * (@long_mask). The @long_mask is ignored if the port corresponding to the pin
 * is not a digital port.
 *
 * Here, we do hotplug irq storm detection and mitigation, and pass further
 * processing to appropriate bottom halves.
 */
void intel_hpd_irq_handler(struct drm_i915_private *dev_priv,
			   u32 pin_mask, u32 long_mask)
{
	struct intel_encoder *encoder;
	bool storm_detected = false;
	bool queue_dig = false, queue_hp = false;
	u32 long_hpd_pulse_mask = 0;
	u32 short_hpd_pulse_mask = 0;
	enum hpd_pin pin;

	if (!pin_mask)
		return;

	spin_lock(&dev_priv->irq_lock);

	/*
	 * Determine whether ->hpd_pulse() exists for each pin, and
	 * whether we have a short or a long pulse. This is needed
	 * as each pin may have up to two encoders (HDMI and DP) and
	 * only the one of them (DP) will have ->hpd_pulse().
	 */
	for_each_intel_encoder(&dev_priv->drm, encoder) {
		bool has_hpd_pulse = intel_encoder_has_hpd_pulse(encoder);
		enum port port = encoder->port;
		bool long_hpd;

		pin = encoder->hpd_pin;
		if (!(BIT(pin) & pin_mask))
			continue;

		if (!has_hpd_pulse)
			continue;

		long_hpd = long_mask & BIT(pin);

		DRM_DEBUG_DRIVER("digital hpd port %c - %s\n", port_name(port),
				 long_hpd ? "long" : "short");
		queue_dig = true;

		if (long_hpd) {
			long_hpd_pulse_mask |= BIT(pin);
			dev_priv->hotplug.long_port_mask |= BIT(port);
		} else {
			short_hpd_pulse_mask |= BIT(pin);
			dev_priv->hotplug.short_port_mask |= BIT(port);
		}
	}

	/* Now process each pin just once */
	for_each_hpd_pin(pin) {
		bool long_hpd;

		if (!(BIT(pin) & pin_mask))
			continue;

		if (dev_priv->hotplug.stats[pin].state == HPD_DISABLED) {
			/*
			 * On GMCH platforms the interrupt mask bits only
			 * prevent irq generation, not the setting of the
			 * hotplug bits itself. So only WARN about unexpected
			 * interrupts on saner platforms.
			 */
			WARN_ONCE(!HAS_GMCH(dev_priv),
				  "Received HPD interrupt on pin %d although disabled\n", pin);
			continue;
		}

		if (dev_priv->hotplug.stats[pin].state != HPD_ENABLED)
			continue;

		/*
		 * Delegate to ->hpd_pulse() if one of the encoders for this
		 * pin has it, otherwise let the hotplug_work deal with this
		 * pin directly.
		 */
		if (((short_hpd_pulse_mask | long_hpd_pulse_mask) & BIT(pin))) {
			long_hpd = long_hpd_pulse_mask & BIT(pin);
		} else {
			dev_priv->hotplug.event_bits |= BIT(pin);
			long_hpd = true;
			queue_hp = true;
		}

		if (intel_hpd_irq_storm_detect(dev_priv, pin, long_hpd)) {
			dev_priv->hotplug.event_bits &= ~BIT(pin);
			storm_detected = true;
			queue_hp = true;
		}
	}

	/*
	 * Disable any IRQs that storms were detected on. Polling enablement
	 * happens later in our hotplug work.
	 */
	if (storm_detected && dev_priv->display_irqs_enabled)
		dev_priv->display.hpd_irq_setup(dev_priv);
	spin_unlock(&dev_priv->irq_lock);

	/*
	 * Our hotplug handler can grab modeset locks (by calling down into the
	 * fb helpers). Hence it must not be run on our own dev-priv->wq work
	 * queue for otherwise the flush_work in the pageflip code will
	 * deadlock.
	 */
	if (queue_dig)
		queue_work(dev_priv->hotplug.dp_wq, &dev_priv->hotplug.dig_port_work);
	if (queue_hp)
		queue_delayed_work(system_wq, &dev_priv->hotplug.hotplug_work, 0);
}

/**
 * intel_hpd_init - initializes and enables hpd support
 * @dev_priv: i915 device instance
 *
 * This function enables the hotplug support. It requires that interrupts have
 * already been enabled with intel_irq_init_hw(). From this point on hotplug and
 * poll request can run concurrently to other code, so locking rules must be
 * obeyed.
 *
 * This is a separate step from interrupt enabling to simplify the locking rules
 * in the driver load and resume code.
 *
 * Also see: intel_hpd_poll_init(), which enables connector polling
 */
void intel_hpd_init(struct drm_i915_private *dev_priv)
{
	int i;

	for_each_hpd_pin(i) {
		dev_priv->hotplug.stats[i].count = 0;
		dev_priv->hotplug.stats[i].state = HPD_ENABLED;
	}

	WRITE_ONCE(dev_priv->hotplug.poll_enabled, false);
	schedule_work(&dev_priv->hotplug.poll_init_work);

	/*
	 * Interrupt setup is already guaranteed to be single-threaded, this is
	 * just to make the assert_spin_locked checks happy.
	 */
	if (dev_priv->display_irqs_enabled && dev_priv->display.hpd_irq_setup) {
		spin_lock_irq(&dev_priv->irq_lock);
		if (dev_priv->display_irqs_enabled)
			dev_priv->display.hpd_irq_setup(dev_priv);
		spin_unlock_irq(&dev_priv->irq_lock);
	}
}

static void i915_hpd_poll_init_work(struct work_struct *work)
{
	struct drm_i915_private *dev_priv =
		container_of(work, struct drm_i915_private,
			     hotplug.poll_init_work);
	struct drm_device *dev = &dev_priv->drm;
	struct drm_connector *connector;
	struct drm_connector_list_iter conn_iter;
	bool enabled;

	mutex_lock(&dev->mode_config.mutex);

	enabled = READ_ONCE(dev_priv->hotplug.poll_enabled);

	drm_connector_list_iter_begin(dev, &conn_iter);
	drm_for_each_connector_iter(connector, &conn_iter) {
		struct intel_connector *intel_connector =
			to_intel_connector(connector);
		connector->polled = intel_connector->polled;

		/* MST has a dynamic intel_connector->encoder and it's reprobing
		 * is all handled by the MST helpers. */
		if (intel_connector->mst_port)
			continue;

		if (!connector->polled && I915_HAS_HOTPLUG(dev_priv) &&
		    intel_connector->encoder->hpd_pin > HPD_NONE) {
			connector->polled = enabled ?
				DRM_CONNECTOR_POLL_CONNECT |
				DRM_CONNECTOR_POLL_DISCONNECT :
				DRM_CONNECTOR_POLL_HPD;
		}
	}
	drm_connector_list_iter_end(&conn_iter);

	if (enabled)
		drm_kms_helper_poll_enable(dev);

	mutex_unlock(&dev->mode_config.mutex);

	/*
	 * We might have missed any hotplugs that happened while we were
	 * in the middle of disabling polling
	 */
	if (!enabled)
		drm_helper_hpd_irq_event(dev);
}

/**
 * intel_hpd_poll_init - enables/disables polling for connectors with hpd
 * @dev_priv: i915 device instance
 *
 * This function enables polling for all connectors, regardless of whether or
 * not they support hotplug detection. Under certain conditions HPD may not be
 * functional. On most Intel GPUs, this happens when we enter runtime suspend.
 * On Valleyview and Cherryview systems, this also happens when we shut off all
 * of the powerwells.
 *
 * Since this function can get called in contexts where we're already holding
 * dev->mode_config.mutex, we do the actual hotplug enabling in a seperate
 * worker.
 *
 * Also see: intel_hpd_init(), which restores hpd handling.
 */
void intel_hpd_poll_init(struct drm_i915_private *dev_priv)
{
	WRITE_ONCE(dev_priv->hotplug.poll_enabled, true);

	/*
	 * We might already be holding dev->mode_config.mutex, so do this in a
	 * seperate worker
	 * As well, there's no issue if we race here since we always reschedule
	 * this worker anyway
	 */
	schedule_work(&dev_priv->hotplug.poll_init_work);
}

void intel_hpd_init_work(struct drm_i915_private *dev_priv)
{
	INIT_DELAYED_WORK(&dev_priv->hotplug.hotplug_work,
			  i915_hotplug_work_func);
	INIT_WORK(&dev_priv->hotplug.dig_port_work, i915_digport_work_func);
	INIT_WORK(&dev_priv->hotplug.poll_init_work, i915_hpd_poll_init_work);
	INIT_DELAYED_WORK(&dev_priv->hotplug.reenable_work,
			  intel_hpd_irq_storm_reenable_work);
}

void intel_hpd_cancel_work(struct drm_i915_private *dev_priv)
{
	spin_lock_irq(&dev_priv->irq_lock);

	dev_priv->hotplug.long_port_mask = 0;
	dev_priv->hotplug.short_port_mask = 0;
	dev_priv->hotplug.event_bits = 0;
	dev_priv->hotplug.retry_bits = 0;

	spin_unlock_irq(&dev_priv->irq_lock);

	cancel_work_sync(&dev_priv->hotplug.dig_port_work);
	cancel_delayed_work_sync(&dev_priv->hotplug.hotplug_work);
	cancel_work_sync(&dev_priv->hotplug.poll_init_work);
	cancel_delayed_work_sync(&dev_priv->hotplug.reenable_work);
}

bool intel_hpd_disable(struct drm_i915_private *dev_priv, enum hpd_pin pin)
{
	bool ret = false;

	if (pin == HPD_NONE)
		return false;

	spin_lock_irq(&dev_priv->irq_lock);
	if (dev_priv->hotplug.stats[pin].state == HPD_ENABLED) {
		dev_priv->hotplug.stats[pin].state = HPD_DISABLED;
		ret = true;
	}
	spin_unlock_irq(&dev_priv->irq_lock);

	return ret;
}

void intel_hpd_enable(struct drm_i915_private *dev_priv, enum hpd_pin pin)
{
	if (pin == HPD_NONE)
		return;

	spin_lock_irq(&dev_priv->irq_lock);
	dev_priv->hotplug.stats[pin].state = HPD_ENABLED;
	spin_unlock_irq(&dev_priv->irq_lock);
}