The hotplug detection routine of i915 uses drm_helper_hpd_irq_event(). This
helper can detect changing of status of connector, but it can not detect 
changing
of edid. Following scenario requires detection of changing of edid.

 1) plug display device to a connector
 2) system suspend
 3) unplug 1)'s display device and plug the other display device to a connector
 4) system resume

It adds edid check routine when a connector status still remains as 
"connector_status_connected".

v2: Add NULL check before comparing of EDIDs.

Testcase: igt/kms_chamelium/hdmi-edid-change-during-hibernate
Testcase: igt/kms_chamelium/hdmi-edid-change-during-suspend
Testcase: igt/kms_chamelium/dp-edid-change-during-hibernate
Testcase: igt/kms_chamelium/dp-edid-change-during-suspend

Signed-off-by: Gwan-gyeong Mun <gwan-gyeong....@intel.com>
---
 drivers/gpu/drm/i915/intel_hotplug.c | 83 +++++++++++++++++++++++++++-
 1 file changed, 82 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_hotplug.c 
b/drivers/gpu/drm/i915/intel_hotplug.c
index 648a13c6043c..0bd3e1c38167 100644
--- a/drivers/gpu/drm/i915/intel_hotplug.c
+++ b/drivers/gpu/drm/i915/intel_hotplug.c
@@ -507,6 +507,87 @@ void intel_hpd_init(struct drm_i915_private *dev_priv)
        }
 }
 
+/**
+ * intel_hpd_irq_event - hotplug processing
+ * @dev: drm_device
+ *
+ * Drivers can use this function to run a detect cycle on all connectors which
+ * have the DRM_CONNECTOR_POLL_HPD flag set in their &polled member. All other
+ * connectors are ignored, which is useful to avoid reprobing fixed panels.
+ *
+ * This function is useful for drivers which can't or don't track hotplug 
interrupts
+ * for each connector. This function is based on drm_helper_hpd_irq_event() 
helper
+ * function and besides it adds edid check routine when a connector status 
still
+ * remains as "connector_status_connected".
+ *
+ * Following scenario requires detection of changing of edid.
+ *  1) plug display device to a connector
+ *  2) system suspend
+ *  3) unplug 1)'s display device and plug the other display device to a 
connector
+ *  4) system resume
+
+ * This function must be called from process context with no mode
+ * setting locks held.
+ *
+ * Note that a connector can be both polled and probed from the hotplug 
handler,
+ * in case the hotplug interrupt is known to be unreliable.
+ */
+static bool intel_hpd_irq_event(struct drm_device *dev)
+{
+       struct drm_connector *connector;
+       struct drm_connector_list_iter conn_iter;
+       enum drm_connector_status old_status, cur_status;
+       struct edid *old_edid;
+       bool changed = false;
+
+       if (!dev->mode_config.poll_enabled)
+               return false;
+
+       mutex_lock(&dev->mode_config.mutex);
+       drm_connector_list_iter_begin(dev, &conn_iter);
+       drm_for_each_connector_iter(connector, &conn_iter) {
+               /* Only handle HPD capable connectors. */
+               if (!(connector->polled & DRM_CONNECTOR_POLL_HPD))
+                       continue;
+
+               old_status = connector->status;
+               old_edid = to_intel_connector(connector)->detect_edid;
+
+               cur_status = drm_helper_probe_detect(connector, NULL, false);
+               DRM_DEBUG_KMS("[CONNECTOR:%d:%s] status updated from %s to 
%s\n",
+                             connector->base.id, connector->name,
+                             drm_get_connector_status_name(old_status),
+                             drm_get_connector_status_name(cur_status));
+
+               if (old_status != cur_status)
+                       changed = true;
+
+               /* Check changing of edid when a connector status still remains
+                * as "connector_status_connected".
+                */
+               if (old_status == cur_status &&
+                   cur_status == connector_status_connected) {
+                       struct edid *cur_edid = 
to_intel_connector(connector)->detect_edid;
+                       if (!old_edid || !cur_edid)
+                               continue;
+
+                       if (memcmp(old_edid, cur_edid, sizeof(*cur_edid))) {
+                               changed = true;
+                               DRM_DEBUG_KMS("[CONNECTOR:%d:%s] edid 
updated\n",
+                                             connector->base.id,
+                                             connector->name);
+                       }
+               }
+       }
+       drm_connector_list_iter_end(&conn_iter);
+       mutex_unlock(&dev->mode_config.mutex);
+
+       if (changed)
+               drm_kms_helper_hotplug_event(dev);
+
+       return changed;
+}
+
 static void i915_hpd_poll_init_work(struct work_struct *work)
 {
        struct drm_i915_private *dev_priv =
@@ -552,7 +633,7 @@ static void i915_hpd_poll_init_work(struct work_struct 
*work)
         * in the middle of disabling polling
         */
        if (!enabled)
-               drm_helper_hpd_irq_event(dev);
+               intel_hpd_irq_event(dev);
 }
 
 /**
-- 
2.18.0

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