[PATCH] drm/i915: Fix the HDMI hot plug disconnection failure (v5)

[Guang Bai]

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.

v2: Fix the formatting issue
v3: Use connector type to apply changes to HDMI port only (James & Matt)
v4: Added debug info for testing
v5: Try local hot-plug call for debugging purpose

Cc: Jani Nikula <jani.nikula at intel.com>
Cc: Chris Chiu <chiu at endlessm.com>
Signed-off-by: Guang Bai <guang.bai at intel.com>
---
 drivers/gpu/drm/i915/intel_hotplug.c | 52 +++++++++++++++++++++++++++++++++++-
 1 file changed, 51 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_hotplug.c b/drivers/gpu/drm/i915/intel_hotplug.c
index e24174d..69870e7 100644
--- a/drivers/gpu/drm/i915/intel_hotplug.c
+++ b/drivers/gpu/drm/i915/intel_hotplug.c
@@ -265,6 +265,53 @@ 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_hpd_encoder_state(struct intel_encoder *encoder,
+			     struct intel_connector *connector)
+{
+	struct drm_device *dev = connector->base.dev;
+	enum drm_connector_status old_status, new_status;
+	int connector_type = connector->base.connector_type;
+	u32 count = 0;
+
+	WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
+	old_status = connector->base.status;
+	/*
+	 * Set HDMI connection status based on hot-plug live states and
+	 * display probe results.
+	 */
+	if (connector_type == DRM_MODE_CONNECTOR_HDMIA ||
+	    connector_type == DRM_MODE_CONNECTOR_HDMIB) {
+		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;
+
+	DRM_DEBUG_KMS("[CONNECTOR:%d:%s] status updated from %s to %s\n",
+		      connector->base.base.id,
+		      connector->base.name,
+		      drm_get_connector_status_name(old_status),
+		      drm_get_connector_status_name(connector->base.status));
+
+	return true;
+}
+
 bool intel_encoder_hotplug(struct intel_encoder *encoder,
 			   struct intel_connector *connector)
 {
@@ -379,9 +426,12 @@ static void i915_hotplug_work_func(struct work_struct *work)
 		if (hpd_event_bits & (1 << intel_encoder->hpd_pin)) {
 			DRM_DEBUG_KMS("Connector %s (pin %i) received hotplug event.\n",
 				      connector->name, intel_encoder->hpd_pin);
-
+			/* tbd gbai3
 			changed |= intel_encoder->hotplug(intel_encoder,
 							  intel_connector);
+			*/
+			changed |= intel_hpd_encoder_state(intel_encoder,
+							     intel_connector);
 		}
 	}
 	drm_connector_list_iter_end(&conn_iter);
-- 
2.7.4