1 /*
2  * Copyright (c) 2006-2008 Intel Corporation
3  * Copyright (c) 2007 Dave Airlie <airlied@linux.ie>
4  *
5  * DRM core CRTC related functions
6  *
7  * Permission to use, copy, modify, distribute, and sell this software and its
8  * documentation for any purpose is hereby granted without fee, provided that
9  * the above copyright notice appear in all copies and that both that copyright
10  * notice and this permission notice appear in supporting documentation, and
11  * that the name of the copyright holders not be used in advertising or
12  * publicity pertaining to distribution of the software without specific,
13  * written prior permission.  The copyright holders make no representations
14  * about the suitability of this software for any purpose.  It is provided "as
15  * is" without express or implied warranty.
16  *
17  * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
18  * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
19  * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
20  * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
21  * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
22  * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
23  * OF THIS SOFTWARE.
24  *
25  * Authors:
26  *      Keith Packard
27  *	Eric Anholt <eric@anholt.net>
28  *      Dave Airlie <airlied@linux.ie>
29  *      Jesse Barnes <jesse.barnes@intel.com>
30  */
31 
32 #include <linux/export.h>
33 #include <linux/moduleparam.h>
34 
35 #include <drm/drmP.h>
36 #include <drm/drm_crtc.h>
37 #include <drm/drm_fourcc.h>
38 #include <drm/drm_crtc_helper.h>
39 #include <drm/drm_fb_helper.h>
40 #include <drm/drm_edid.h>
41 #include <drm/drm_modeset_helper_vtables.h>
42 
43 #include "drm_crtc_helper_internal.h"
44 
45 /**
46  * DOC: output probing helper overview
47  *
48  * This library provides some helper code for output probing. It provides an
49  * implementation of the core &drm_connector_funcs.fill_modes interface with
50  * drm_helper_probe_single_connector_modes().
51  *
52  * It also provides support for polling connectors with a work item and for
53  * generic hotplug interrupt handling where the driver doesn't or cannot keep
54  * track of a per-connector hpd interrupt.
55  *
56  * This helper library can be used independently of the modeset helper library.
57  * Drivers can also overwrite different parts e.g. use their own hotplug
58  * handling code to avoid probing unrelated outputs.
59  *
60  * The probe helpers share the function table structures with other display
61  * helper libraries. See &struct drm_connector_helper_funcs for the details.
62  */
63 
64 static bool drm_kms_helper_poll = true;
65 module_param_named(poll, drm_kms_helper_poll, bool, 0600);
66 
67 static enum drm_mode_status
68 drm_mode_validate_flag(const struct drm_display_mode *mode,
69 		       int flags)
70 {
71 	if ((mode->flags & DRM_MODE_FLAG_INTERLACE) &&
72 	    !(flags & DRM_MODE_FLAG_INTERLACE))
73 		return MODE_NO_INTERLACE;
74 
75 	if ((mode->flags & DRM_MODE_FLAG_DBLSCAN) &&
76 	    !(flags & DRM_MODE_FLAG_DBLSCAN))
77 		return MODE_NO_DBLESCAN;
78 
79 	if ((mode->flags & DRM_MODE_FLAG_3D_MASK) &&
80 	    !(flags & DRM_MODE_FLAG_3D_MASK))
81 		return MODE_NO_STEREO;
82 
83 	return MODE_OK;
84 }
85 
86 static enum drm_mode_status
87 drm_mode_validate_pipeline(struct drm_display_mode *mode,
88 			    struct drm_connector *connector)
89 {
90 	struct drm_device *dev = connector->dev;
91 	uint32_t *ids = connector->encoder_ids;
92 	enum drm_mode_status ret = MODE_OK;
93 	unsigned int i;
94 
95 	/* Step 1: Validate against connector */
96 	ret = drm_connector_mode_valid(connector, mode);
97 	if (ret != MODE_OK)
98 		return ret;
99 
100 	/* Step 2: Validate against encoders and crtcs */
101 	for (i = 0; i < DRM_CONNECTOR_MAX_ENCODER; i++) {
102 		struct drm_encoder *encoder = drm_encoder_find(dev, NULL, ids[i]);
103 		struct drm_crtc *crtc;
104 
105 		if (!encoder)
106 			continue;
107 
108 		ret = drm_encoder_mode_valid(encoder, mode);
109 		if (ret != MODE_OK) {
110 			/* No point in continuing for crtc check as this encoder
111 			 * will not accept the mode anyway. If all encoders
112 			 * reject the mode then, at exit, ret will not be
113 			 * MODE_OK. */
114 			continue;
115 		}
116 
117 		ret = drm_bridge_mode_valid(encoder->bridge, mode);
118 		if (ret != MODE_OK) {
119 			/* There is also no point in continuing for crtc check
120 			 * here. */
121 			continue;
122 		}
123 
124 		drm_for_each_crtc(crtc, dev) {
125 			if (!drm_encoder_crtc_ok(encoder, crtc))
126 				continue;
127 
128 			ret = drm_crtc_mode_valid(crtc, mode);
129 			if (ret == MODE_OK) {
130 				/* If we get to this point there is at least
131 				 * one combination of encoder+crtc that works
132 				 * for this mode. Lets return now. */
133 				return ret;
134 			}
135 		}
136 	}
137 
138 	return ret;
139 }
140 
141 static int drm_helper_probe_add_cmdline_mode(struct drm_connector *connector)
142 {
143 	struct drm_cmdline_mode *cmdline_mode;
144 	struct drm_display_mode *mode;
145 
146 	cmdline_mode = &connector->cmdline_mode;
147 	if (!cmdline_mode->specified)
148 		return 0;
149 
150 	/* Only add a GTF mode if we find no matching probed modes */
151 	list_for_each_entry(mode, &connector->probed_modes, head) {
152 		if (mode->hdisplay != cmdline_mode->xres ||
153 		    mode->vdisplay != cmdline_mode->yres)
154 			continue;
155 
156 		if (cmdline_mode->refresh_specified) {
157 			/* The probed mode's vrefresh is set until later */
158 			if (drm_mode_vrefresh(mode) != cmdline_mode->refresh)
159 				continue;
160 		}
161 
162 		return 0;
163 	}
164 
165 	mode = drm_mode_create_from_cmdline_mode(connector->dev,
166 						 cmdline_mode);
167 	if (mode == NULL)
168 		return 0;
169 
170 	drm_mode_probed_add(connector, mode);
171 	return 1;
172 }
173 
174 enum drm_mode_status drm_crtc_mode_valid(struct drm_crtc *crtc,
175 					 const struct drm_display_mode *mode)
176 {
177 	const struct drm_crtc_helper_funcs *crtc_funcs = crtc->helper_private;
178 
179 	if (!crtc_funcs || !crtc_funcs->mode_valid)
180 		return MODE_OK;
181 
182 	return crtc_funcs->mode_valid(crtc, mode);
183 }
184 
185 enum drm_mode_status drm_encoder_mode_valid(struct drm_encoder *encoder,
186 					    const struct drm_display_mode *mode)
187 {
188 	const struct drm_encoder_helper_funcs *encoder_funcs =
189 		encoder->helper_private;
190 
191 	if (!encoder_funcs || !encoder_funcs->mode_valid)
192 		return MODE_OK;
193 
194 	return encoder_funcs->mode_valid(encoder, mode);
195 }
196 
197 enum drm_mode_status drm_connector_mode_valid(struct drm_connector *connector,
198 					      struct drm_display_mode *mode)
199 {
200 	const struct drm_connector_helper_funcs *connector_funcs =
201 		connector->helper_private;
202 
203 	if (!connector_funcs || !connector_funcs->mode_valid)
204 		return MODE_OK;
205 
206 	return connector_funcs->mode_valid(connector, mode);
207 }
208 
209 #define DRM_OUTPUT_POLL_PERIOD (10*HZ)
210 /**
211  * drm_kms_helper_poll_enable - re-enable output polling.
212  * @dev: drm_device
213  *
214  * This function re-enables the output polling work, after it has been
215  * temporarily disabled using drm_kms_helper_poll_disable(), for example over
216  * suspend/resume.
217  *
218  * Drivers can call this helper from their device resume implementation. It is
219  * not an error to call this even when output polling isn't enabled.
220  *
221  * Note that calls to enable and disable polling must be strictly ordered, which
222  * is automatically the case when they're only call from suspend/resume
223  * callbacks.
224  */
225 void drm_kms_helper_poll_enable(struct drm_device *dev)
226 {
227 	bool poll = false;
228 	struct drm_connector *connector;
229 	struct drm_connector_list_iter conn_iter;
230 	unsigned long delay = DRM_OUTPUT_POLL_PERIOD;
231 
232 	if (!dev->mode_config.poll_enabled || !drm_kms_helper_poll)
233 		return;
234 
235 	drm_connector_list_iter_begin(dev, &conn_iter);
236 	drm_for_each_connector_iter(connector, &conn_iter) {
237 		if (connector->polled & (DRM_CONNECTOR_POLL_CONNECT |
238 					 DRM_CONNECTOR_POLL_DISCONNECT))
239 			poll = true;
240 	}
241 	drm_connector_list_iter_end(&conn_iter);
242 
243 	if (dev->mode_config.delayed_event) {
244 		/*
245 		 * FIXME:
246 		 *
247 		 * Use short (1s) delay to handle the initial delayed event.
248 		 * This delay should not be needed, but Optimus/nouveau will
249 		 * fail in a mysterious way if the delayed event is handled as
250 		 * soon as possible like it is done in
251 		 * drm_helper_probe_single_connector_modes() in case the poll
252 		 * was enabled before.
253 		 */
254 		poll = true;
255 		delay = HZ;
256 	}
257 
258 	if (poll)
259 		schedule_delayed_work(&dev->mode_config.output_poll_work, delay);
260 }
261 EXPORT_SYMBOL(drm_kms_helper_poll_enable);
262 
263 static enum drm_connector_status
264 drm_helper_probe_detect_ctx(struct drm_connector *connector, bool force)
265 {
266 	const struct drm_connector_helper_funcs *funcs = connector->helper_private;
267 	struct drm_modeset_acquire_ctx ctx;
268 	int ret;
269 
270 	drm_modeset_acquire_init(&ctx, 0);
271 
272 retry:
273 	ret = drm_modeset_lock(&connector->dev->mode_config.connection_mutex, &ctx);
274 	if (!ret) {
275 		if (funcs->detect_ctx)
276 			ret = funcs->detect_ctx(connector, &ctx, force);
277 		else if (connector->funcs->detect)
278 			ret = connector->funcs->detect(connector, force);
279 		else
280 			ret = connector_status_connected;
281 	}
282 
283 	if (ret == -EDEADLK) {
284 		drm_modeset_backoff(&ctx);
285 		goto retry;
286 	}
287 
288 	if (WARN_ON(ret < 0))
289 		ret = connector_status_unknown;
290 
291 	drm_modeset_drop_locks(&ctx);
292 	drm_modeset_acquire_fini(&ctx);
293 
294 	return ret;
295 }
296 
297 /**
298  * drm_helper_probe_detect - probe connector status
299  * @connector: connector to probe
300  * @ctx: acquire_ctx, or NULL to let this function handle locking.
301  * @force: Whether destructive probe operations should be performed.
302  *
303  * This function calls the detect callbacks of the connector.
304  * This function returns &drm_connector_status, or
305  * if @ctx is set, it might also return -EDEADLK.
306  */
307 int
308 drm_helper_probe_detect(struct drm_connector *connector,
309 			struct drm_modeset_acquire_ctx *ctx,
310 			bool force)
311 {
312 	const struct drm_connector_helper_funcs *funcs = connector->helper_private;
313 	struct drm_device *dev = connector->dev;
314 	int ret;
315 
316 	if (!ctx)
317 		return drm_helper_probe_detect_ctx(connector, force);
318 
319 	ret = drm_modeset_lock(&dev->mode_config.connection_mutex, ctx);
320 	if (ret)
321 		return ret;
322 
323 	if (funcs->detect_ctx)
324 		return funcs->detect_ctx(connector, ctx, force);
325 	else if (connector->funcs->detect)
326 		return connector->funcs->detect(connector, force);
327 	else
328 		return connector_status_connected;
329 }
330 EXPORT_SYMBOL(drm_helper_probe_detect);
331 
332 /**
333  * drm_helper_probe_single_connector_modes - get complete set of display modes
334  * @connector: connector to probe
335  * @maxX: max width for modes
336  * @maxY: max height for modes
337  *
338  * Based on the helper callbacks implemented by @connector in struct
339  * &drm_connector_helper_funcs try to detect all valid modes.  Modes will first
340  * be added to the connector's probed_modes list, then culled (based on validity
341  * and the @maxX, @maxY parameters) and put into the normal modes list.
342  *
343  * Intended to be used as a generic implementation of the
344  * &drm_connector_funcs.fill_modes() vfunc for drivers that use the CRTC helpers
345  * for output mode filtering and detection.
346  *
347  * The basic procedure is as follows
348  *
349  * 1. All modes currently on the connector's modes list are marked as stale
350  *
351  * 2. New modes are added to the connector's probed_modes list with
352  *    drm_mode_probed_add(). New modes start their life with status as OK.
353  *    Modes are added from a single source using the following priority order.
354  *
355  *    - &drm_connector_helper_funcs.get_modes vfunc
356  *    - if the connector status is connector_status_connected, standard
357  *      VESA DMT modes up to 1024x768 are automatically added
358  *      (drm_add_modes_noedid())
359  *
360  *    Finally modes specified via the kernel command line (video=...) are
361  *    added in addition to what the earlier probes produced
362  *    (drm_helper_probe_add_cmdline_mode()). These modes are generated
363  *    using the VESA GTF/CVT formulas.
364  *
365  * 3. Modes are moved from the probed_modes list to the modes list. Potential
366  *    duplicates are merged together (see drm_mode_connector_list_update()).
367  *    After this step the probed_modes list will be empty again.
368  *
369  * 4. Any non-stale mode on the modes list then undergoes validation
370  *
371  *    - drm_mode_validate_basic() performs basic sanity checks
372  *    - drm_mode_validate_size() filters out modes larger than @maxX and @maxY
373  *      (if specified)
374  *    - drm_mode_validate_flag() checks the modes against basic connector
375  *      capabilities (interlace_allowed,doublescan_allowed,stereo_allowed)
376  *    - the optional &drm_connector_helper_funcs.mode_valid helper can perform
377  *      driver and/or sink specific checks
378  *    - the optional &drm_crtc_helper_funcs.mode_valid,
379  *      &drm_bridge_funcs.mode_valid and &drm_encoder_helper_funcs.mode_valid
380  *      helpers can perform driver and/or source specific checks which are also
381  *      enforced by the modeset/atomic helpers
382  *
383  * 5. Any mode whose status is not OK is pruned from the connector's modes list,
384  *    accompanied by a debug message indicating the reason for the mode's
385  *    rejection (see drm_mode_prune_invalid()).
386  *
387  * Returns:
388  * The number of modes found on @connector.
389  */
390 int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
391 					    uint32_t maxX, uint32_t maxY)
392 {
393 	struct drm_device *dev = connector->dev;
394 	struct drm_display_mode *mode;
395 	const struct drm_connector_helper_funcs *connector_funcs =
396 		connector->helper_private;
397 	int count = 0, ret;
398 	int mode_flags = 0;
399 	bool verbose_prune = true;
400 	enum drm_connector_status old_status;
401 	struct drm_modeset_acquire_ctx ctx;
402 
403 	WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
404 
405 	drm_modeset_acquire_init(&ctx, 0);
406 
407 	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", connector->base.id,
408 			connector->name);
409 
410 retry:
411 	ret = drm_modeset_lock(&dev->mode_config.connection_mutex, &ctx);
412 	if (ret == -EDEADLK) {
413 		drm_modeset_backoff(&ctx);
414 		goto retry;
415 	} else
416 		WARN_ON(ret < 0);
417 
418 	/* set all old modes to the stale state */
419 	list_for_each_entry(mode, &connector->modes, head)
420 		mode->status = MODE_STALE;
421 
422 	old_status = connector->status;
423 
424 	if (connector->force) {
425 		if (connector->force == DRM_FORCE_ON ||
426 		    connector->force == DRM_FORCE_ON_DIGITAL)
427 			connector->status = connector_status_connected;
428 		else
429 			connector->status = connector_status_disconnected;
430 		if (connector->funcs->force)
431 			connector->funcs->force(connector);
432 	} else {
433 		ret = drm_helper_probe_detect(connector, &ctx, true);
434 
435 		if (ret == -EDEADLK) {
436 			drm_modeset_backoff(&ctx);
437 			goto retry;
438 		} else if (WARN(ret < 0, "Invalid return value %i for connector detection\n", ret))
439 			ret = connector_status_unknown;
440 
441 		connector->status = ret;
442 	}
443 
444 	/*
445 	 * Normally either the driver's hpd code or the poll loop should
446 	 * pick up any changes and fire the hotplug event. But if
447 	 * userspace sneaks in a probe, we might miss a change. Hence
448 	 * check here, and if anything changed start the hotplug code.
449 	 */
450 	if (old_status != connector->status) {
451 		DRM_DEBUG_KMS("[CONNECTOR:%d:%s] status updated from %s to %s\n",
452 			      connector->base.id,
453 			      connector->name,
454 			      drm_get_connector_status_name(old_status),
455 			      drm_get_connector_status_name(connector->status));
456 
457 		/*
458 		 * The hotplug event code might call into the fb
459 		 * helpers, and so expects that we do not hold any
460 		 * locks. Fire up the poll struct instead, it will
461 		 * disable itself again.
462 		 */
463 		dev->mode_config.delayed_event = true;
464 		if (dev->mode_config.poll_enabled)
465 			schedule_delayed_work(&dev->mode_config.output_poll_work,
466 					      0);
467 	}
468 
469 	/* Re-enable polling in case the global poll config changed. */
470 	if (drm_kms_helper_poll != dev->mode_config.poll_running)
471 		drm_kms_helper_poll_enable(dev);
472 
473 	dev->mode_config.poll_running = drm_kms_helper_poll;
474 
475 	if (connector->status == connector_status_disconnected) {
476 		DRM_DEBUG_KMS("[CONNECTOR:%d:%s] disconnected\n",
477 			connector->base.id, connector->name);
478 		drm_mode_connector_update_edid_property(connector, NULL);
479 		verbose_prune = false;
480 		goto prune;
481 	}
482 
483 	count = (*connector_funcs->get_modes)(connector);
484 
485 	if (count == 0 && connector->status == connector_status_connected)
486 		count = drm_add_modes_noedid(connector, 1024, 768);
487 	count += drm_helper_probe_add_cmdline_mode(connector);
488 	if (count == 0)
489 		goto prune;
490 
491 	drm_mode_connector_list_update(connector);
492 
493 	if (connector->interlace_allowed)
494 		mode_flags |= DRM_MODE_FLAG_INTERLACE;
495 	if (connector->doublescan_allowed)
496 		mode_flags |= DRM_MODE_FLAG_DBLSCAN;
497 	if (connector->stereo_allowed)
498 		mode_flags |= DRM_MODE_FLAG_3D_MASK;
499 
500 	list_for_each_entry(mode, &connector->modes, head) {
501 		if (mode->status == MODE_OK)
502 			mode->status = drm_mode_validate_basic(mode);
503 
504 		if (mode->status == MODE_OK)
505 			mode->status = drm_mode_validate_size(mode, maxX, maxY);
506 
507 		if (mode->status == MODE_OK)
508 			mode->status = drm_mode_validate_flag(mode, mode_flags);
509 
510 		if (mode->status == MODE_OK)
511 			mode->status = drm_mode_validate_pipeline(mode,
512 								  connector);
513 
514 		if (mode->status == MODE_OK)
515 			mode->status = drm_mode_validate_ycbcr420(mode,
516 								  connector);
517 	}
518 
519 prune:
520 	drm_mode_prune_invalid(dev, &connector->modes, verbose_prune);
521 
522 	drm_modeset_drop_locks(&ctx);
523 	drm_modeset_acquire_fini(&ctx);
524 
525 	if (list_empty(&connector->modes))
526 		return 0;
527 
528 	list_for_each_entry(mode, &connector->modes, head)
529 		mode->vrefresh = drm_mode_vrefresh(mode);
530 
531 	drm_mode_sort(&connector->modes);
532 
533 	DRM_DEBUG_KMS("[CONNECTOR:%d:%s] probed modes :\n", connector->base.id,
534 			connector->name);
535 	list_for_each_entry(mode, &connector->modes, head) {
536 		drm_mode_set_crtcinfo(mode, CRTC_INTERLACE_HALVE_V);
537 		drm_mode_debug_printmodeline(mode);
538 	}
539 
540 	return count;
541 }
542 EXPORT_SYMBOL(drm_helper_probe_single_connector_modes);
543 
544 /**
545  * drm_kms_helper_hotplug_event - fire off KMS hotplug events
546  * @dev: drm_device whose connector state changed
547  *
548  * This function fires off the uevent for userspace and also calls the
549  * output_poll_changed function, which is most commonly used to inform the fbdev
550  * emulation code and allow it to update the fbcon output configuration.
551  *
552  * Drivers should call this from their hotplug handling code when a change is
553  * detected. Note that this function does not do any output detection of its
554  * own, like drm_helper_hpd_irq_event() does - this is assumed to be done by the
555  * driver already.
556  *
557  * This function must be called from process context with no mode
558  * setting locks held.
559  */
560 void drm_kms_helper_hotplug_event(struct drm_device *dev)
561 {
562 	/* send a uevent + call fbdev */
563 	drm_sysfs_hotplug_event(dev);
564 	if (dev->mode_config.funcs->output_poll_changed)
565 		dev->mode_config.funcs->output_poll_changed(dev);
566 }
567 EXPORT_SYMBOL(drm_kms_helper_hotplug_event);
568 
569 static void output_poll_execute(struct work_struct *work)
570 {
571 	struct delayed_work *delayed_work = to_delayed_work(work);
572 	struct drm_device *dev = container_of(delayed_work, struct drm_device, mode_config.output_poll_work);
573 	struct drm_connector *connector;
574 	struct drm_connector_list_iter conn_iter;
575 	enum drm_connector_status old_status;
576 	bool repoll = false, changed;
577 
578 	/* Pick up any changes detected by the probe functions. */
579 	changed = dev->mode_config.delayed_event;
580 	dev->mode_config.delayed_event = false;
581 
582 	if (!drm_kms_helper_poll)
583 		goto out;
584 
585 	if (!mutex_trylock(&dev->mode_config.mutex)) {
586 		repoll = true;
587 		goto out;
588 	}
589 
590 	drm_connector_list_iter_begin(dev, &conn_iter);
591 	drm_for_each_connector_iter(connector, &conn_iter) {
592 		/* Ignore forced connectors. */
593 		if (connector->force)
594 			continue;
595 
596 		/* Ignore HPD capable connectors and connectors where we don't
597 		 * want any hotplug detection at all for polling. */
598 		if (!connector->polled || connector->polled == DRM_CONNECTOR_POLL_HPD)
599 			continue;
600 
601 		old_status = connector->status;
602 		/* if we are connected and don't want to poll for disconnect
603 		   skip it */
604 		if (old_status == connector_status_connected &&
605 		    !(connector->polled & DRM_CONNECTOR_POLL_DISCONNECT))
606 			continue;
607 
608 		repoll = true;
609 
610 		connector->status = drm_helper_probe_detect(connector, NULL, false);
611 		if (old_status != connector->status) {
612 			const char *old, *new;
613 
614 			/*
615 			 * The poll work sets force=false when calling detect so
616 			 * that drivers can avoid to do disruptive tests (e.g.
617 			 * when load detect cycles could cause flickering on
618 			 * other, running displays). This bears the risk that we
619 			 * flip-flop between unknown here in the poll work and
620 			 * the real state when userspace forces a full detect
621 			 * call after receiving a hotplug event due to this
622 			 * change.
623 			 *
624 			 * Hence clamp an unknown detect status to the old
625 			 * value.
626 			 */
627 			if (connector->status == connector_status_unknown) {
628 				connector->status = old_status;
629 				continue;
630 			}
631 
632 			old = drm_get_connector_status_name(old_status);
633 			new = drm_get_connector_status_name(connector->status);
634 
635 			DRM_DEBUG_KMS("[CONNECTOR:%d:%s] "
636 				      "status updated from %s to %s\n",
637 				      connector->base.id,
638 				      connector->name,
639 				      old, new);
640 
641 			changed = true;
642 		}
643 	}
644 	drm_connector_list_iter_end(&conn_iter);
645 
646 	mutex_unlock(&dev->mode_config.mutex);
647 
648 out:
649 	if (changed)
650 		drm_kms_helper_hotplug_event(dev);
651 
652 	if (repoll)
653 		schedule_delayed_work(delayed_work, DRM_OUTPUT_POLL_PERIOD);
654 }
655 
656 /**
657  * drm_kms_helper_is_poll_worker - is %current task an output poll worker?
658  *
659  * Determine if %current task is an output poll worker.  This can be used
660  * to select distinct code paths for output polling versus other contexts.
661  *
662  * One use case is to avoid a deadlock between the output poll worker and
663  * the autosuspend worker wherein the latter waits for polling to finish
664  * upon calling drm_kms_helper_poll_disable(), while the former waits for
665  * runtime suspend to finish upon calling pm_runtime_get_sync() in a
666  * connector ->detect hook.
667  */
668 bool drm_kms_helper_is_poll_worker(void)
669 {
670 	struct work_struct *work = current_work();
671 
672 	return work && work->func == output_poll_execute;
673 }
674 EXPORT_SYMBOL(drm_kms_helper_is_poll_worker);
675 
676 /**
677  * drm_kms_helper_poll_disable - disable output polling
678  * @dev: drm_device
679  *
680  * This function disables the output polling work.
681  *
682  * Drivers can call this helper from their device suspend implementation. It is
683  * not an error to call this even when output polling isn't enabled or already
684  * disabled. Polling is re-enabled by calling drm_kms_helper_poll_enable().
685  *
686  * Note that calls to enable and disable polling must be strictly ordered, which
687  * is automatically the case when they're only call from suspend/resume
688  * callbacks.
689  */
690 void drm_kms_helper_poll_disable(struct drm_device *dev)
691 {
692 	if (!dev->mode_config.poll_enabled)
693 		return;
694 	cancel_delayed_work_sync(&dev->mode_config.output_poll_work);
695 }
696 EXPORT_SYMBOL(drm_kms_helper_poll_disable);
697 
698 /**
699  * drm_kms_helper_poll_init - initialize and enable output polling
700  * @dev: drm_device
701  *
702  * This function intializes and then also enables output polling support for
703  * @dev. Drivers which do not have reliable hotplug support in hardware can use
704  * this helper infrastructure to regularly poll such connectors for changes in
705  * their connection state.
706  *
707  * Drivers can control which connectors are polled by setting the
708  * DRM_CONNECTOR_POLL_CONNECT and DRM_CONNECTOR_POLL_DISCONNECT flags. On
709  * connectors where probing live outputs can result in visual distortion drivers
710  * should not set the DRM_CONNECTOR_POLL_DISCONNECT flag to avoid this.
711  * Connectors which have no flag or only DRM_CONNECTOR_POLL_HPD set are
712  * completely ignored by the polling logic.
713  *
714  * Note that a connector can be both polled and probed from the hotplug handler,
715  * in case the hotplug interrupt is known to be unreliable.
716  */
717 void drm_kms_helper_poll_init(struct drm_device *dev)
718 {
719 	INIT_DELAYED_WORK(&dev->mode_config.output_poll_work, output_poll_execute);
720 	dev->mode_config.poll_enabled = true;
721 
722 	drm_kms_helper_poll_enable(dev);
723 }
724 EXPORT_SYMBOL(drm_kms_helper_poll_init);
725 
726 /**
727  * drm_kms_helper_poll_fini - disable output polling and clean it up
728  * @dev: drm_device
729  */
730 void drm_kms_helper_poll_fini(struct drm_device *dev)
731 {
732 	drm_kms_helper_poll_disable(dev);
733 }
734 EXPORT_SYMBOL(drm_kms_helper_poll_fini);
735 
736 /**
737  * drm_helper_hpd_irq_event - hotplug processing
738  * @dev: drm_device
739  *
740  * Drivers can use this helper function to run a detect cycle on all connectors
741  * which have the DRM_CONNECTOR_POLL_HPD flag set in their &polled member. All
742  * other connectors are ignored, which is useful to avoid reprobing fixed
743  * panels.
744  *
745  * This helper function is useful for drivers which can't or don't track hotplug
746  * interrupts for each connector.
747  *
748  * Drivers which support hotplug interrupts for each connector individually and
749  * which have a more fine-grained detect logic should bypass this code and
750  * directly call drm_kms_helper_hotplug_event() in case the connector state
751  * changed.
752  *
753  * This function must be called from process context with no mode
754  * setting locks held.
755  *
756  * Note that a connector can be both polled and probed from the hotplug handler,
757  * in case the hotplug interrupt is known to be unreliable.
758  */
759 bool drm_helper_hpd_irq_event(struct drm_device *dev)
760 {
761 	struct drm_connector *connector;
762 	struct drm_connector_list_iter conn_iter;
763 	enum drm_connector_status old_status;
764 	bool changed = false;
765 
766 	if (!dev->mode_config.poll_enabled)
767 		return false;
768 
769 	mutex_lock(&dev->mode_config.mutex);
770 	drm_connector_list_iter_begin(dev, &conn_iter);
771 	drm_for_each_connector_iter(connector, &conn_iter) {
772 		/* Only handle HPD capable connectors. */
773 		if (!(connector->polled & DRM_CONNECTOR_POLL_HPD))
774 			continue;
775 
776 		old_status = connector->status;
777 
778 		connector->status = drm_helper_probe_detect(connector, NULL, false);
779 		DRM_DEBUG_KMS("[CONNECTOR:%d:%s] status updated from %s to %s\n",
780 			      connector->base.id,
781 			      connector->name,
782 			      drm_get_connector_status_name(old_status),
783 			      drm_get_connector_status_name(connector->status));
784 		if (old_status != connector->status)
785 			changed = true;
786 	}
787 	drm_connector_list_iter_end(&conn_iter);
788 	mutex_unlock(&dev->mode_config.mutex);
789 
790 	if (changed)
791 		drm_kms_helper_hotplug_event(dev);
792 
793 	return changed;
794 }
795 EXPORT_SYMBOL(drm_helper_hpd_irq_event);
796