Patch "drm/i915/vlv: Disable HPD in valleyview_crt_detect_hotplug()" has been added to the 4.7-stable tree

@@ -2791,6 +2791,8 @@ void intel_hpd_init(struct drm_i915_priv
 void intel_hpd_init_work(struct drm_i915_private *dev_priv);
 void intel_hpd_cancel_work(struct drm_i915_private *dev_priv);
 bool intel_hpd_pin_to_port(enum hpd_pin pin, enum port *port);
+bool intel_hpd_disable(struct drm_i915_private *dev_priv, enum hpd_pin pin);
+void intel_hpd_enable(struct drm_i915_private *dev_priv, enum hpd_pin pin);
 
 /* i915_irq.c */
 void i915_queue_hangcheck(struct drm_device *dev);

@@ -327,10 +327,25 @@ static bool valleyview_crt_detect_hotplu
 	struct drm_device *dev = connector->dev;
 	struct intel_crt *crt = intel_attached_crt(connector);
 	struct drm_i915_private *dev_priv = dev->dev_private;
+	bool reenable_hpd;
 	u32 adpa;
 	bool ret;
 	u32 save_adpa;
 
+	/*
+	 * Doing a force trigger causes a hpd interrupt to get sent, which can
+	 * get us stuck in a loop if we're polling:
+	 *  - We enable power wells and reset the ADPA
+	 *  - output_poll_exec does force probe on VGA, triggering a hpd
+	 *  - HPD handler waits for poll to unlock dev->mode_config.mutex
+	 *  - output_poll_exec shuts off the ADPA, unlocks
+	 *    dev->mode_config.mutex
+	 *  - HPD handler runs, resets ADPA and brings us back to the start
+	 *
+	 * Just disable HPD interrupts here to prevent this
+	 */
+	reenable_hpd = intel_hpd_disable(dev_priv, crt->base.hpd_pin);
+
 	save_adpa = adpa = I915_READ(crt->adpa_reg);
 	DRM_DEBUG_KMS("trigger hotplug detect cycle: adpa=0x%x\n", adpa);
 

@@ -353,6 +368,9 @@ static bool valleyview_crt_detect_hotplu
 
 	DRM_DEBUG_KMS("valleyview hotplug adpa=0x%x, result %d\n", adpa, ret);
 
+	if (reenable_hpd)
+		intel_hpd_enable(dev_priv, crt->base.hpd_pin);
+
 	return ret;
 }
 

@@ -511,3 +511,30 @@ void intel_hpd_cancel_work(struct drm_i9
 	cancel_work_sync(&dev_priv->hotplug.hotplug_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);
+}