drivers/gpu/drm/i915/intel_hotplug.c

   1 /*
   2  * Copyright © 2015 Intel Corporation
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  21  * IN THE SOFTWARE.
  22  */
  23
  24 #include <linux/kernel.h>
  25
  26 #include <drm/drmP.h>
  27 #include <drm/i915_drm.h>
  28
  29 #include "i915_drv.h"
  30 #include "intel_drv.h"
  31
  32 /**
  33  * DOC: Hotplug
  34  *
  35  * Simply put, hotplug occurs when a display is connected to or disconnected
  36  * from the system. However, there may be adapters and docking stations and
  37  * Display Port short pulses and MST devices involved, complicating matters.
  38  *
  39  * Hotplug in i915 is handled in many different levels of abstraction.
  40  *
  41  * The platform dependent interrupt handling code in i915_irq.c enables,
  42  * disables, and does preliminary handling of the interrupts. The interrupt
  43  * handlers gather the hotplug detect (HPD) information from relevant registers
  44  * into a platform independent mask of hotplug pins that have fired.
  45  *
  46  * The platform independent interrupt handler intel_hpd_irq_handler() in
  47  * intel_hotplug.c does hotplug irq storm detection and mitigation, and passes
  48  * further processing to appropriate bottom halves (Display Port specific and
  49  * regular hotplug).
  50  *
  51  * The Display Port work function i915_digport_work_func() calls into
  52  * intel_dp_hpd_pulse() via hooks, which handles DP short pulses and DP MST long
  53  * pulses, with failures and non-MST long pulses triggering regular hotplug
  54  * processing on the connector.
  55  *
  56  * The regular hotplug work function i915_hotplug_work_func() calls connector
  57  * detect hooks, and, if connector status changes, triggers sending of hotplug
  58  * uevent to userspace via drm_kms_helper_hotplug_event().
  59  *
  60  * Finally, the userspace is responsible for triggering a modeset upon receiving
  61  * the hotplug uevent, disabling or enabling the crtc as needed.
  62  *
  63  * The hotplug interrupt storm detection and mitigation code keeps track of the
  64  * number of interrupts per hotplug pin per a period of time, and if the number
  65  * of interrupts exceeds a certain threshold, the interrupt is disabled for a
  66  * while before being re-enabled. The intention is to mitigate issues raising
  67  * from broken hardware triggering massive amounts of interrupts and grinding
  68  * the system to a halt.
  69  *
  70  * Current implementation expects that hotplug interrupt storm will not be
  71  * seen when display port sink is connected, hence on platforms whose DP
  72  * callback is handled by i915_digport_work_func reenabling of hpd is not
  73  * performed (it was never expected to be disabled in the first place ;) )
  74  * this is specific to DP sinks handled by this routine and any other display
  75  * such as HDMI or DVI enabled on the same port will have proper logic since
  76  * it will use i915_hotplug_work_func where this logic is handled.
  77  */
  78
  79 /**
  80  * intel_hpd_port - return port hard associated with certain pin.
  81  * @pin: the hpd pin to get associated port
  82  *
  83  * Return port that is associatade with @pin and PORT_NONE if no port is
  84  * hard associated with that @pin.
  85  */
  86 enum port intel_hpd_pin_to_port(enum hpd_pin pin)
  87 {
  88         switch (pin) {
  89         case HPD_PORT_A:
  90                 return PORT_A;
  91         case HPD_PORT_B:
  92                 return PORT_B;
  93         case HPD_PORT_C:
  94                 return PORT_C;
  95         case HPD_PORT_D:
  96                 return PORT_D;
  97         case HPD_PORT_E:
  98                 return PORT_E;
  99         default:
 100                 return PORT_NONE; /* no port for this pin */
 101         }
 102 }
 103
 104 /**
 105  * intel_hpd_pin - return pin hard associated with certain port.
 106  * @port: the hpd port to get associated pin
 107  *
 108  * Return pin that is associatade with @port and HDP_NONE if no pin is
 109  * hard associated with that @port.
 110  */
 111 enum hpd_pin intel_hpd_pin(enum port port)
 112 {
 113         switch (port) {
 114         case PORT_A:
 115                 return HPD_PORT_A;
 116         case PORT_B:
 117                 return HPD_PORT_B;
 118         case PORT_C:
 119                 return HPD_PORT_C;
 120         case PORT_D:
 121                 return HPD_PORT_D;
 122         case PORT_E:
 123                 return HPD_PORT_E;
 124         default:
 125                 MISSING_CASE(port);
 126                 return HPD_NONE;
 127         }
 128 }
 129
 130 #define HPD_STORM_DETECT_PERIOD         1000
 131 #define HPD_STORM_REENABLE_DELAY        (2 * 60 * 1000)
 132
 133 /**
 134  * intel_hpd_irq_storm_detect - gather stats and detect HPD irq storm on a pin
 135  * @dev_priv: private driver data pointer
 136  * @pin: the pin to gather stats on
 137  *
 138  * Gather stats about HPD irqs from the specified @pin, and detect irq
 139  * storms. Only the pin specific stats and state are changed, the caller is
 140  * responsible for further action.
 141  *
 142  * The number of irqs that are allowed within @HPD_STORM_DETECT_PERIOD is
 143  * stored in @dev_priv->hotplug.hpd_storm_threshold which defaults to
 144  * @HPD_STORM_DEFAULT_THRESHOLD. If this threshold is exceeded, it's
 145  * considered an irq storm and the irq state is set to @HPD_MARK_DISABLED.
 146  *
 147  * The HPD threshold can be controlled through i915_hpd_storm_ctl in debugfs,
 148  * and should only be adjusted for automated hotplug testing.
 149  *
 150  * Return true if an irq storm was detected on @pin.
 151  */
 152 static bool intel_hpd_irq_storm_detect(struct drm_i915_private *dev_priv,
 153                                        enum hpd_pin pin)
 154 {
 155         unsigned long start = dev_priv->hotplug.stats[pin].last_jiffies;
 156         unsigned long end = start + msecs_to_jiffies(HPD_STORM_DETECT_PERIOD);
 157         const int threshold = dev_priv->hotplug.hpd_storm_threshold;
 158         bool storm = false;
 159
 160         if (!time_in_range(jiffies, start, end)) {
 161                 dev_priv->hotplug.stats[pin].last_jiffies = jiffies;
 162                 dev_priv->hotplug.stats[pin].count = 0;
 163                 DRM_DEBUG_KMS("Received HPD interrupt on PIN %d - cnt: 0\n", pin);
 164         } else if (dev_priv->hotplug.stats[pin].count > threshold &&
 165                    threshold) {
 166                 dev_priv->hotplug.stats[pin].state = HPD_MARK_DISABLED;
 167                 DRM_DEBUG_KMS("HPD interrupt storm detected on PIN %d\n", pin);
 168                 storm = true;
 169         } else {
 170                 dev_priv->hotplug.stats[pin].count++;
 171                 DRM_DEBUG_KMS("Received HPD interrupt on PIN %d - cnt: %d\n", pin,
 172                               dev_priv->hotplug.stats[pin].count);
 173         }
 174
 175         return storm;
 176 }
 177
 178 static void intel_hpd_irq_storm_disable(struct drm_i915_private *dev_priv)
 179 {
 180         struct drm_device *dev = &dev_priv->drm;
 181         struct intel_connector *intel_connector;
 182         struct intel_encoder *intel_encoder;
 183         struct drm_connector *connector;
 184         struct drm_connector_list_iter conn_iter;
 185         enum hpd_pin pin;
 186         bool hpd_disabled = false;
 187
 188         lockdep_assert_held(&dev_priv->irq_lock);
 189
 190         drm_connector_list_iter_begin(dev, &conn_iter);
 191         drm_for_each_connector_iter(connector, &conn_iter) {
 192                 if (connector->polled != DRM_CONNECTOR_POLL_HPD)
 193                         continue;
 194
 195                 intel_connector = to_intel_connector(connector);
 196                 intel_encoder = intel_connector->encoder;
 197                 if (!intel_encoder)
 198                         continue;
 199
 200                 pin = intel_encoder->hpd_pin;
 201                 if (pin == HPD_NONE ||
 202                     dev_priv->hotplug.stats[pin].state != HPD_MARK_DISABLED)
 203                         continue;
 204
 205                 DRM_INFO("HPD interrupt storm detected on connector %s: "
 206                          "switching from hotplug detection to polling\n",
 207                          connector->name);
 208
 209                 dev_priv->hotplug.stats[pin].state = HPD_DISABLED;
 210                 connector->polled = DRM_CONNECTOR_POLL_CONNECT
 211                         | DRM_CONNECTOR_POLL_DISCONNECT;
 212                 hpd_disabled = true;
 213         }
 214         drm_connector_list_iter_end(&conn_iter);
 215
 216         /* Enable polling and queue hotplug re-enabling. */
 217         if (hpd_disabled) {
 218                 drm_kms_helper_poll_enable(dev);
 219                 mod_delayed_work(system_wq, &dev_priv->hotplug.reenable_work,
 220                                  msecs_to_jiffies(HPD_STORM_REENABLE_DELAY));
 221         }
 222 }
 223
 224 static void intel_hpd_irq_storm_reenable_work(struct work_struct *work)
 225 {
 226         struct drm_i915_private *dev_priv =
 227                 container_of(work, typeof(*dev_priv),
 228                              hotplug.reenable_work.work);
 229         struct drm_device *dev = &dev_priv->drm;
 230         int i;
 231
 232         intel_runtime_pm_get(dev_priv);
 233
 234         spin_lock_irq(&dev_priv->irq_lock);
 235         for_each_hpd_pin(i) {
 236                 struct drm_connector *connector;
 237                 struct drm_connector_list_iter conn_iter;
 238
 239                 if (dev_priv->hotplug.stats[i].state != HPD_DISABLED)
 240                         continue;
 241
 242                 dev_priv->hotplug.stats[i].state = HPD_ENABLED;
 243
 244                 drm_connector_list_iter_begin(dev, &conn_iter);
 245                 drm_for_each_connector_iter(connector, &conn_iter) {
 246                         struct intel_connector *intel_connector = to_intel_connector(connector);
 247
 248                         if (intel_connector->encoder->hpd_pin == i) {
 249                                 if (connector->polled != intel_connector->polled)
 250                                         DRM_DEBUG_DRIVER("Reenabling HPD on connector %s\n",
 251                                                          connector->name);
 252                                 connector->polled = intel_connector->polled;
 253                                 if (!connector->polled)
 254                                         connector->polled = DRM_CONNECTOR_POLL_HPD;
 255                         }
 256                 }
 257                 drm_connector_list_iter_end(&conn_iter);
 258         }
 259         if (dev_priv->display_irqs_enabled && dev_priv->display.hpd_irq_setup)
 260                 dev_priv->display.hpd_irq_setup(dev_priv);
 261         spin_unlock_irq(&dev_priv->irq_lock);
 262
 263         intel_runtime_pm_put(dev_priv);
 264 }
 265
 266 static bool intel_hpd_irq_event(struct drm_device *dev,
 267                                 struct drm_connector *connector)
 268 {
 269         enum drm_connector_status old_status;
 270
 271         WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
 272         old_status = connector->status;
 273
 274         connector->status = drm_helper_probe_detect(connector, NULL, false);
 275
 276         if (old_status == connector->status)
 277                 return false;
 278
 279         DRM_DEBUG_KMS("[CONNECTOR:%d:%s] status updated from %s to %s\n",
 280                       connector->base.id,
 281                       connector->name,
 282                       drm_get_connector_status_name(old_status),
 283                       drm_get_connector_status_name(connector->status));
 284
 285         return true;
 286 }
 287
 288 static void i915_digport_work_func(struct work_struct *work)
 289 {
 290         struct drm_i915_private *dev_priv =
 291                 container_of(work, struct drm_i915_private, hotplug.dig_port_work);
 292         u32 long_port_mask, short_port_mask;
 293         struct intel_digital_port *intel_dig_port;
 294         int i;
 295         u32 old_bits = 0;
 296
 297         spin_lock_irq(&dev_priv->irq_lock);
 298         long_port_mask = dev_priv->hotplug.long_port_mask;
 299         dev_priv->hotplug.long_port_mask = 0;
 300         short_port_mask = dev_priv->hotplug.short_port_mask;
 301         dev_priv->hotplug.short_port_mask = 0;
 302         spin_unlock_irq(&dev_priv->irq_lock);
 303
 304         for (i = 0; i < I915_MAX_PORTS; i++) {
 305                 bool valid = false;
 306                 bool long_hpd = false;
 307                 intel_dig_port = dev_priv->hotplug.irq_port[i];
 308                 if (!intel_dig_port || !intel_dig_port->hpd_pulse)
 309                         continue;
 310
 311                 if (long_port_mask & (1 << i))  {
 312                         valid = true;
 313                         long_hpd = true;
 314                 } else if (short_port_mask & (1 << i))
 315                         valid = true;
 316
 317                 if (valid) {
 318                         enum irqreturn ret;
 319
 320                         ret = intel_dig_port->hpd_pulse(intel_dig_port, long_hpd);
 321                         if (ret == IRQ_NONE) {
 322                                 /* fall back to old school hpd */
 323                                 old_bits |= (1 << intel_dig_port->base.hpd_pin);
 324                         }
 325                 }
 326         }
 327
 328         if (old_bits) {
 329                 spin_lock_irq(&dev_priv->irq_lock);
 330                 dev_priv->hotplug.event_bits |= old_bits;
 331                 spin_unlock_irq(&dev_priv->irq_lock);
 332                 schedule_work(&dev_priv->hotplug.hotplug_work);
 333         }
 334 }
 335
 336 /*
 337  * Handle hotplug events outside the interrupt handler proper.
 338  */
 339 static void i915_hotplug_work_func(struct work_struct *work)
 340 {
 341         struct drm_i915_private *dev_priv =
 342                 container_of(work, struct drm_i915_private, hotplug.hotplug_work);
 343         struct drm_device *dev = &dev_priv->drm;
 344         struct intel_connector *intel_connector;
 345         struct intel_encoder *intel_encoder;
 346         struct drm_connector *connector;
 347         struct drm_connector_list_iter conn_iter;
 348         bool changed = false;
 349         u32 hpd_event_bits;
 350
 351         mutex_lock(&dev->mode_config.mutex);
 352         DRM_DEBUG_KMS("running encoder hotplug functions\n");
 353
 354         spin_lock_irq(&dev_priv->irq_lock);
 355
 356         hpd_event_bits = dev_priv->hotplug.event_bits;
 357         dev_priv->hotplug.event_bits = 0;
 358
 359         /* Disable hotplug on connectors that hit an irq storm. */
 360         intel_hpd_irq_storm_disable(dev_priv);
 361
 362         spin_unlock_irq(&dev_priv->irq_lock);
 363
 364         drm_connector_list_iter_begin(dev, &conn_iter);
 365         drm_for_each_connector_iter(connector, &conn_iter) {
 366                 intel_connector = to_intel_connector(connector);
 367                 if (!intel_connector->encoder)
 368                         continue;
 369                 intel_encoder = intel_connector->encoder;
 370                 if (hpd_event_bits & (1 << intel_encoder->hpd_pin)) {
 371                         DRM_DEBUG_KMS("Connector %s (pin %i) received hotplug event.\n",
 372                                       connector->name, intel_encoder->hpd_pin);
 373                         if (intel_encoder->hot_plug)
 374                                 intel_encoder->hot_plug(intel_encoder);
 375                         if (intel_hpd_irq_event(dev, connector))
 376                                 changed = true;
 377                 }
 378         }
 379         drm_connector_list_iter_end(&conn_iter);
 380         mutex_unlock(&dev->mode_config.mutex);
 381
 382         if (changed)
 383                 drm_kms_helper_hotplug_event(dev);
 384 }
 385
 386
 387 /**
 388  * intel_hpd_irq_handler - main hotplug irq handler
 389  * @dev_priv: drm_i915_private
 390  * @pin_mask: a mask of hpd pins that have triggered the irq
 391  * @long_mask: a mask of hpd pins that may be long hpd pulses
 392  *
 393  * This is the main hotplug irq handler for all platforms. The platform specific
 394  * irq handlers call the platform specific hotplug irq handlers, which read and
 395  * decode the appropriate registers into bitmasks about hpd pins that have
 396  * triggered (@pin_mask), and which of those pins may be long pulses
 397  * (@long_mask). The @long_mask is ignored if the port corresponding to the pin
 398  * is not a digital port.
 399  *
 400  * Here, we do hotplug irq storm detection and mitigation, and pass further
 401  * processing to appropriate bottom halves.
 402  */
 403 void intel_hpd_irq_handler(struct drm_i915_private *dev_priv,
 404                            u32 pin_mask, u32 long_mask)
 405 {
 406         int i;
 407         enum port port;
 408         bool storm_detected = false;
 409         bool queue_dig = false, queue_hp = false;
 410         bool is_dig_port;
 411
 412         if (!pin_mask)
 413                 return;
 414
 415         spin_lock(&dev_priv->irq_lock);
 416         for_each_hpd_pin(i) {
 417                 if (!(BIT(i) & pin_mask))
 418                         continue;
 419
 420                 port = intel_hpd_pin_to_port(i);
 421                 is_dig_port = port != PORT_NONE &&
 422                         dev_priv->hotplug.irq_port[port];
 423
 424                 if (is_dig_port) {
 425                         bool long_hpd = long_mask & BIT(i);
 426
 427                         DRM_DEBUG_DRIVER("digital hpd port %c - %s\n", port_name(port),
 428                                          long_hpd ? "long" : "short");
 429                         /*
 430                          * For long HPD pulses we want to have the digital queue happen,
 431                          * but we still want HPD storm detection to function.
 432                          */
 433                         queue_dig = true;
 434                         if (long_hpd) {
 435                                 dev_priv->hotplug.long_port_mask |= (1 << port);
 436                         } else {
 437                                 /* for short HPD just trigger the digital queue */
 438                                 dev_priv->hotplug.short_port_mask |= (1 << port);
 439                                 continue;
 440                         }
 441                 }
 442
 443                 if (dev_priv->hotplug.stats[i].state == HPD_DISABLED) {
 444                         /*
 445                          * On GMCH platforms the interrupt mask bits only
 446                          * prevent irq generation, not the setting of the
 447                          * hotplug bits itself. So only WARN about unexpected
 448                          * interrupts on saner platforms.
 449                          */
 450                         WARN_ONCE(!HAS_GMCH_DISPLAY(dev_priv),
 451                                   "Received HPD interrupt on pin %d although disabled\n", i);
 452                         continue;
 453                 }
 454
 455                 if (dev_priv->hotplug.stats[i].state != HPD_ENABLED)
 456                         continue;
 457
 458                 if (!is_dig_port) {
 459                         dev_priv->hotplug.event_bits |= BIT(i);
 460                         queue_hp = true;
 461                 }
 462
 463                 if (intel_hpd_irq_storm_detect(dev_priv, i)) {
 464                         dev_priv->hotplug.event_bits &= ~BIT(i);
 465                         storm_detected = true;
 466                 }
 467         }
 468
 469         if (storm_detected && dev_priv->display_irqs_enabled)
 470                 dev_priv->display.hpd_irq_setup(dev_priv);
 471         spin_unlock(&dev_priv->irq_lock);
 472
 473         /*
 474          * Our hotplug handler can grab modeset locks (by calling down into the
 475          * fb helpers). Hence it must not be run on our own dev-priv->wq work
 476          * queue for otherwise the flush_work in the pageflip code will
 477          * deadlock.
 478          */
 479         if (queue_dig)
 480                 queue_work(dev_priv->hotplug.dp_wq, &dev_priv->hotplug.dig_port_work);
 481         if (queue_hp)
 482                 schedule_work(&dev_priv->hotplug.hotplug_work);
 483 }
 484
 485 /**
 486  * intel_hpd_init - initializes and enables hpd support
 487  * @dev_priv: i915 device instance
 488  *
 489  * This function enables the hotplug support. It requires that interrupts have
 490  * already been enabled with intel_irq_init_hw(). From this point on hotplug and
 491  * poll request can run concurrently to other code, so locking rules must be
 492  * obeyed.
 493  *
 494  * This is a separate step from interrupt enabling to simplify the locking rules
 495  * in the driver load and resume code.
 496  *
 497  * Also see: intel_hpd_poll_init(), which enables connector polling
 498  */
 499 void intel_hpd_init(struct drm_i915_private *dev_priv)
 500 {
 501         int i;
 502
 503         for_each_hpd_pin(i) {
 504                 dev_priv->hotplug.stats[i].count = 0;
 505                 dev_priv->hotplug.stats[i].state = HPD_ENABLED;
 506         }
 507
 508         WRITE_ONCE(dev_priv->hotplug.poll_enabled, false);
 509         schedule_work(&dev_priv->hotplug.poll_init_work);
 510
 511         /*
 512          * Interrupt setup is already guaranteed to be single-threaded, this is
 513          * just to make the assert_spin_locked checks happy.
 514          */
 515         if (dev_priv->display_irqs_enabled && dev_priv->display.hpd_irq_setup) {
 516                 spin_lock_irq(&dev_priv->irq_lock);
 517                 if (dev_priv->display_irqs_enabled)
 518                         dev_priv->display.hpd_irq_setup(dev_priv);
 519                 spin_unlock_irq(&dev_priv->irq_lock);
 520         }
 521 }
 522
 523 static void i915_hpd_poll_init_work(struct work_struct *work)
 524 {
 525         struct drm_i915_private *dev_priv =
 526                 container_of(work, struct drm_i915_private,
 527                              hotplug.poll_init_work);
 528         struct drm_device *dev = &dev_priv->drm;
 529         struct drm_connector *connector;
 530         struct drm_connector_list_iter conn_iter;
 531         bool enabled;
 532
 533         mutex_lock(&dev->mode_config.mutex);
 534
 535         enabled = READ_ONCE(dev_priv->hotplug.poll_enabled);
 536
 537         drm_connector_list_iter_begin(dev, &conn_iter);
 538         drm_for_each_connector_iter(connector, &conn_iter) {
 539                 struct intel_connector *intel_connector =
 540                         to_intel_connector(connector);
 541                 connector->polled = intel_connector->polled;
 542
 543                 /* MST has a dynamic intel_connector->encoder and it's reprobing
 544                  * is all handled by the MST helpers. */
 545                 if (intel_connector->mst_port)
 546                         continue;
 547
 548                 if (!connector->polled && I915_HAS_HOTPLUG(dev_priv) &&
 549                     intel_connector->encoder->hpd_pin > HPD_NONE) {
 550                         connector->polled = enabled ?
 551                                 DRM_CONNECTOR_POLL_CONNECT |
 552                                 DRM_CONNECTOR_POLL_DISCONNECT :
 553                                 DRM_CONNECTOR_POLL_HPD;
 554                 }
 555         }
 556         drm_connector_list_iter_end(&conn_iter);
 557
 558         if (enabled)
 559                 drm_kms_helper_poll_enable(dev);
 560
 561         mutex_unlock(&dev->mode_config.mutex);
 562
 563         /*
 564          * We might have missed any hotplugs that happened while we were
 565          * in the middle of disabling polling
 566          */
 567         if (!enabled)
 568                 drm_helper_hpd_irq_event(dev);
 569 }
 570
 571 /**
 572  * intel_hpd_poll_init - enables/disables polling for connectors with hpd
 573  * @dev_priv: i915 device instance
 574  *
 575  * This function enables polling for all connectors, regardless of whether or
 576  * not they support hotplug detection. Under certain conditions HPD may not be
 577  * functional. On most Intel GPUs, this happens when we enter runtime suspend.
 578  * On Valleyview and Cherryview systems, this also happens when we shut off all
 579  * of the powerwells.
 580  *
 581  * Since this function can get called in contexts where we're already holding
 582  * dev->mode_config.mutex, we do the actual hotplug enabling in a seperate
 583  * worker.
 584  *
 585  * Also see: intel_hpd_init(), which restores hpd handling.
 586  */
 587 void intel_hpd_poll_init(struct drm_i915_private *dev_priv)
 588 {
 589         WRITE_ONCE(dev_priv->hotplug.poll_enabled, true);
 590
 591         /*
 592          * We might already be holding dev->mode_config.mutex, so do this in a
 593          * seperate worker
 594          * As well, there's no issue if we race here since we always reschedule
 595          * this worker anyway
 596          */
 597         schedule_work(&dev_priv->hotplug.poll_init_work);
 598 }
 599
 600 void intel_hpd_init_work(struct drm_i915_private *dev_priv)
 601 {
 602         INIT_WORK(&dev_priv->hotplug.hotplug_work, i915_hotplug_work_func);
 603         INIT_WORK(&dev_priv->hotplug.dig_port_work, i915_digport_work_func);
 604         INIT_WORK(&dev_priv->hotplug.poll_init_work, i915_hpd_poll_init_work);
 605         INIT_DELAYED_WORK(&dev_priv->hotplug.reenable_work,
 606                           intel_hpd_irq_storm_reenable_work);
 607 }
 608
 609 void intel_hpd_cancel_work(struct drm_i915_private *dev_priv)
 610 {
 611         spin_lock_irq(&dev_priv->irq_lock);
 612
 613         dev_priv->hotplug.long_port_mask = 0;
 614         dev_priv->hotplug.short_port_mask = 0;
 615         dev_priv->hotplug.event_bits = 0;
 616
 617         spin_unlock_irq(&dev_priv->irq_lock);
 618
 619         cancel_work_sync(&dev_priv->hotplug.dig_port_work);
 620         cancel_work_sync(&dev_priv->hotplug.hotplug_work);
 621         cancel_work_sync(&dev_priv->hotplug.poll_init_work);
 622         cancel_delayed_work_sync(&dev_priv->hotplug.reenable_work);
 623 }
 624
 625 bool intel_hpd_disable(struct drm_i915_private *dev_priv, enum hpd_pin pin)
 626 {
 627         bool ret = false;
 628
 629         if (pin == HPD_NONE)
 630                 return false;
 631
 632         spin_lock_irq(&dev_priv->irq_lock);
 633         if (dev_priv->hotplug.stats[pin].state == HPD_ENABLED) {
 634                 dev_priv->hotplug.stats[pin].state = HPD_DISABLED;
 635                 ret = true;
 636         }
 637         spin_unlock_irq(&dev_priv->irq_lock);
 638
 639         return ret;
 640 }
 641
 642 void intel_hpd_enable(struct drm_i915_private *dev_priv, enum hpd_pin pin)
 643 {
 644         if (pin == HPD_NONE)
 645                 return;
 646
 647         spin_lock_irq(&dev_priv->irq_lock);
 648         dev_priv->hotplug.stats[pin].state = HPD_ENABLED;
 649         spin_unlock_irq(&dev_priv->irq_lock);
 650 }