[PATCH 02/12] drm/i915: Keep the connector polled state disabled after storm

[Imre Deak]

If an HPD IRQ storm is detected on a connector during driver loading or
system suspend/resume - disabling the IRQ and switching to polling - the
polling may get disabled too early - before the intended 2 minute
HPD_STORM_REENABLE_DELAY - with the HPD IRQ staying disabled for this
duration. One such sequence is:

Thread#1                                   Thread#2
intel_display_driver_probe()->
  intel_hpd_init()->
    (HPD IRQ gets enabled)
  .                                        intel_hpd_irq_handler()->
  .                                          intel_hpd_irq_storm_detect()
  .                                            intel_hpd_irq_setup()->
  .                                              (HPD IRQ gets disabled)
  .                                         queue_delayed_work(hotplug.hotplug_work)
  .                                         ...
  .                                         i915_hotplug_work_func()->
  .                                           intel_hpd_irq_storm_switch_to_polling()->
  .                                             (polling enabled)
  .
  intel_hpd_poll_disable()->
    queue_work(hotplug.poll_init_work)
  ...
  i915_hpd_poll_init_work()->
    (polling gets disabled,
     HPD IRQ is still disabled)
  ...

  (Connector is neither polled or
   detected via HPD IRQs for 2 minutes)

  intel_hpd_irq_storm_reenable_work()->
    (HPD IRQ gets enabled)

To avoid the above 2 minute state without either polling or enabled HPD
IRQ, leave the connector's polling mode unchanged in
i915_hpd_poll_init_work() if its HPD IRQ got disabled after an IRQ storm
indicated by the connector's HPD_DISABLED pin state.

Signed-off-by: Imre Deak <imre.deak at intel.com>
---
 drivers/gpu/drm/i915/display/intel_hotplug.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_hotplug.c b/drivers/gpu/drm/i915/display/intel_hotplug.c
index 0c0700c6ec66d..74513c3d3690b 100644
--- a/drivers/gpu/drm/i915/display/intel_hotplug.c
+++ b/drivers/gpu/drm/i915/display/intel_hotplug.c
@@ -710,6 +710,8 @@ static void i915_hpd_poll_init_work(struct work_struct *work)
 		cancel_work(&dev_priv->display.hotplug.poll_init_work);
 	}
 
+	spin_lock_irq(&dev_priv->irq_lock);
+
 	drm_connector_list_iter_begin(&dev_priv->drm, &conn_iter);
 	for_each_intel_connector_iter(connector, &conn_iter) {
 		enum hpd_pin pin;
@@ -718,6 +720,9 @@ static void i915_hpd_poll_init_work(struct work_struct *work)
 		if (pin == HPD_NONE)
 			continue;
 
+		if (dev_priv->display.hotplug.stats[pin].state == HPD_DISABLED)
+			continue;
+
 		connector->base.polled = connector->polled;
 
 		if (enabled && connector->base.polled == DRM_CONNECTOR_POLL_HPD)
@@ -726,6 +731,8 @@ static void i915_hpd_poll_init_work(struct work_struct *work)
 	}
 	drm_connector_list_iter_end(&conn_iter);
 
+	spin_unlock_irq(&dev_priv->irq_lock);
+
 	if (enabled)
 		drm_kms_helper_poll_reschedule(&dev_priv->drm);
 
-- 
2.39.2