[PATCH] drm/i915: Fix the HDMI hot plug disconnection failure

[Guang Bai <guang.bai@intel.com>]

On some platforms, slowly unplugging (wiggling) the HDMI cable makes
the kernel to believe the HDMI display still connected. This is because
the HDMI DDC lines are disconnected sometimes later after the hot-plug
interrupt triggered. Use the hot plug live states to honor HDMI hot plug
status in addtion to access the DDC channels.

Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Chris Chiu <chiu@endlessm.com>
Signed-off-by: Guang Bai <guang.bai@intel.com>
---
 drivers/gpu/drm/i915/intel_hotplug.c | 31 ++++++++++++++++++++++++++++---
 1 file changed, 28 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_hotplug.c b/drivers/gpu/drm/i915/intel_hotplug.c
index 648a13c..db6288f 100644
--- a/drivers/gpu/drm/i915/intel_hotplug.c
+++ b/drivers/gpu/drm/i915/intel_hotplug.c
@@ -246,17 +246,42 @@ static void intel_hpd_irq_storm_reenable_work(struct work_struct *work)
 	intel_runtime_pm_put(dev_priv);
 }
 
+#define MAX_SHORT_PULSE_MS	100
+#define PORT_CHECK_LOOP_COUNT	3
+
 bool intel_encoder_hotplug(struct intel_encoder *encoder,
 			   struct intel_connector *connector)
 {
 	struct drm_device *dev = connector->base.dev;
-	enum drm_connector_status old_status;
+	enum drm_connector_status old_status, new_status;
+	enum hpd_pin pin = encoder->hpd_pin;
+	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
+	u32 count = 0;
 
 	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);
+	/*
+	 * Set HDMI connection status based on hot-plug live states and
+	 * display probe results.
+	 */
+	if ((encoder->type == INTEL_OUTPUT_HDMI ||
+	     encoder->type == INTEL_OUTPUT_DDI) &&
+	    dev_priv->hotplug.stats[pin].state == HPD_ENABLED) {
+		do {
+			new_status = connector_status_disconnected;
+			msleep(MAX_SHORT_PULSE_MS);
+
+			if (intel_digital_port_connected(encoder))
+				new_status = drm_helper_probe_detect(&connector->base,
+								     NULL, false);
+			if (new_status == connector_status_connected)
+				break;
+		} while (++count <= PORT_CHECK_LOOP_COUNT);
+		connector->base.status = new_status;
+	} else
+		connector->base.status =
+			drm_helper_probe_detect(&connector->base, NULL, false);
 
 	if (old_status == connector->base.status)
 		return false;
-- 
2.7.4

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