[Intel-gfx] [PATCH 3/5] drm/i915: Read HDMI EDID only when required

[Sonika Jindal]

From: Shashank Sharma <shashank.sharma at intel.com>

This patch makes sure that the HDMI detect function
reads EDID only when its forced to do it. All the other
times, it uses the connector->detect_edid which was cached
during hotplug handling in the hdmi_probe() function. As the
probe function gets called before detect in the interrupt handler
and handles the EDID cacheing part, its absolutely safe to assume
that presence of EDID reflects monitor connected and viceversa.

This will save us from many race conditions between hotplug/unplug
detect call handler threads and userspace calls for the same.
The previous patch in this patch series explains this in detail.

Signed-off-by: Shashank Sharma <shashank.sharma at intel.com>
---
 drivers/gpu/drm/i915/intel_hdmi.c |   26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
index 064ddd8..1fb6919 100644
--- a/drivers/gpu/drm/i915/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/intel_hdmi.c
@@ -1362,19 +1362,33 @@ static enum drm_connector_status
 intel_hdmi_detect(struct drm_connector *connector, bool force)
 {
 	enum drm_connector_status status;
+	struct intel_connector *intel_connector =
+				to_intel_connector(connector);
 
 	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
 		      connector->base.id, connector->name);
+	/*
+	 * There are many userspace calls which probe EDID from
+	 * detect path. In case on multiple hotplug/unplug, these
+	 * can cause race conditions while probing EDID. Also its
+	 * waste of CPU cycles to read the EDID again and again
+	 * unless there is a real hotplug.
+	 * So until we are forced, check connector status
+	 * based on availability of cached EDID. This will avoid many of
+	 * these race conditions and timing problems.
+	 */
+	if (force)
+		intel_hdmi_probe(intel_connector->encoder);
 
-	intel_hdmi_unset_edid(connector);
-
-	if (intel_hdmi_set_edid(connector)) {
+	if (intel_connector->detect_edid) {
 		struct intel_hdmi *intel_hdmi = intel_attached_hdmi(connector);
-
-		hdmi_to_dig_port(intel_hdmi)->base.type = INTEL_OUTPUT_HDMI;
 		status = connector_status_connected;
-	} else
+		hdmi_to_dig_port(intel_hdmi)->base.type = INTEL_OUTPUT_HDMI;
+		DRM_DEBUG_DRIVER("hdmi status = connected\n");
+	} else {
 		status = connector_status_disconnected;
+		DRM_DEBUG_DRIVER("hdmi status = disconnected\n");
+	}
 
 	return status;
 }
-- 
1.7.10.4