drm: Introduce epoch counter to drm_connector

This counter will be used by drm_helper_probe_detect caller to determine
if anything had changed(including edid, connection status and etc).
Hardware specific driver detect hooks are responsible for updating this
counter when some change is detected to notify the drm part,
which can trigger for example hotplug event.

Also now call drm_connector_update_edid_property
right after we get edid always to make sure there is a
unified way to handle edid change, without having to
change tons of source code as currently
drm_connector_update_edid_property is called only in
certain cases like reprobing and not right after edid is
actually updated.

v2: Added documentation for the new counter. Rename change_counter to
    epoch_counter.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105540

Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200630002700.5451-3-kunal1.joshi@intel.com

drivers/gpu/drm/drm_connector.c

@@ -269,6 +269,7 @@ int drm_connector_init(struct drm_device *dev,
 	INIT_LIST_HEAD(&connector->modes);
 	mutex_init(&connector->mutex);
 	connector->edid_blob_ptr = NULL;
+	connector->epoch_counter = 0;
 	connector->tile_blob_ptr = NULL;
 	connector->status = connector_status_unknown;
 	connector->display_info.panel_orientation =
@@ -1979,6 +1980,7 @@ int drm_connector_update_edid_property(struct drm_connector *connector,
 	struct drm_device *dev = connector->dev;
 	size_t size = 0;
 	int ret;
+	const struct edid *old_edid;
 
 	/* ignore requests to set edid when overridden */
 	if (connector->override_edid)
@@ -2002,6 +2004,20 @@ int drm_connector_update_edid_property(struct drm_connector *connector,
 
 	drm_update_tile_info(connector, edid);
 
+	if (connector->edid_blob_ptr) {
+		old_edid = (const struct edid *)connector->edid_blob_ptr->data;
+		if (old_edid) {
+			if (!drm_edid_are_equal(edid, old_edid)) {
+				DRM_DEBUG_KMS("[CONNECTOR:%d:%s] Edid was changed.\n",
+					      connector->base.id, connector->name);
+
+				connector->epoch_counter += 1;
+				DRM_DEBUG_KMS("Updating change counter to %llu\n",
+					      connector->epoch_counter);
+			}
+		}
+	}
+
 	drm_object_property_set_value(&connector->base,
 				      dev->mode_config.non_desktop_property,
 				      connector->display_info.non_desktop);

drivers/gpu/drm/drm_edid.c

@@ -1632,7 +1632,6 @@ bool drm_edid_are_equal(const struct edid *edid1, const struct edid *edid2)
 		return false;
 
 	if (edid1) {
-
 		edid1_len = EDID_LENGTH * (1 + edid1->extensions);
 		edid2_len = EDID_LENGTH * (1 + edid2->extensions);
 
@@ -1647,7 +1646,6 @@ bool drm_edid_are_equal(const struct edid *edid1, const struct edid *edid2)
 }
 EXPORT_SYMBOL(drm_edid_are_equal);
 
-
 /**
  * drm_edid_block_valid - Sanity check the EDID block (base or extension)
  * @raw_edid: pointer to raw EDID block
@@ -2050,13 +2048,17 @@ EXPORT_SYMBOL(drm_probe_ddc);
 struct edid *drm_get_edid(struct drm_connector *connector,
 			  struct i2c_adapter *adapter)
 {
+	struct edid *edid;
+
 	if (connector->force == DRM_FORCE_OFF)
 		return NULL;
 
 	if (connector->force == DRM_FORCE_UNSPECIFIED && !drm_probe_ddc(adapter))
 		return NULL;
 
-	return drm_do_get_edid(connector, drm_do_probe_ddc_edid, adapter);
+	edid = drm_do_get_edid(connector, drm_do_probe_ddc_edid, adapter);
+	drm_connector_update_edid_property(connector, edid);
+	return edid;
 }
 EXPORT_SYMBOL(drm_get_edid);
 

drivers/gpu/drm/drm_probe_helper.c

@@ -292,6 +292,9 @@ retry:
 	if (WARN_ON(ret < 0))
 		ret = connector_status_unknown;
 
+	if (ret != connector->status)
+		connector->epoch_counter += 1;
+
 	drm_modeset_drop_locks(&ctx);
 	drm_modeset_acquire_fini(&ctx);
 
@@ -325,11 +328,16 @@ drm_helper_probe_detect(struct drm_connector *connector,
 		return ret;
 
 	if (funcs->detect_ctx)
-		return funcs->detect_ctx(connector, ctx, force);
+		ret = funcs->detect_ctx(connector, ctx, force);
 	else if (connector->funcs->detect)
-		return connector->funcs->detect(connector, force);
+		ret = connector->funcs->detect(connector, force);
 	else
-		return connector_status_connected;
+		ret = connector_status_connected;
+
+	if (ret != connector->status)
+		connector->epoch_counter += 1;
+
+	return ret;
 }
 EXPORT_SYMBOL(drm_helper_probe_detect);
 
@@ -779,6 +787,7 @@ bool drm_helper_hpd_irq_event(struct drm_device *dev)
 	struct drm_connector_list_iter conn_iter;
 	enum drm_connector_status old_status;
 	bool changed = false;
+	u64 old_epoch_counter;
 
 	if (!dev->mode_config.poll_enabled)
 		return false;
@@ -792,20 +801,39 @@ bool drm_helper_hpd_irq_event(struct drm_device *dev)
 
 		old_status = connector->status;
 
+		old_epoch_counter = connector->epoch_counter;
+
+		DRM_DEBUG_KMS("[CONNECTOR:%d:%s] Old epoch counter %llu\n", connector->base.id,
+			      connector->name,
+			      old_epoch_counter);
+
 		connector->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(connector->status));
-		if (old_status != connector->status)
+
+		DRM_DEBUG_KMS("[CONNECTOR:%d:%s] New epoch counter %llu\n",
+			      connector->base.id,
+			      connector->name,
+			      connector->epoch_counter);
+
+		/*
+		 * Check if epoch counter had changed, meaning that we need
+		 * to send a uevent.
+		 */
+		if (old_epoch_counter != connector->epoch_counter)
 			changed = true;
+
 	}
 	drm_connector_list_iter_end(&conn_iter);
 	mutex_unlock(&dev->mode_config.mutex);
 
-	if (changed)
+	if (changed) {
 		drm_kms_helper_hotplug_event(dev);
+		DRM_DEBUG_KMS("Sent hotplug event\n");
+	}
 
 	return changed;
 }

include/drm/drm_connector.h

@@ -1329,6 +1329,8 @@ struct drm_connector {
 	enum drm_connector_force force;
 	/** @override_edid: has the EDID been overwritten through debugfs for testing? */
 	bool override_edid;
+	/** @epoch_counter: used to detect any other changes in connector, besides status */
+	u64 epoch_counter;
 
 	/**
 	 * @possible_encoders: Bit mask of encoders that can drive this