drm/amd/display: Grab dc_lock before detecting link

[Why & How]
There is chance we change dc state while calling dc_link_detect().
As the result of that, grab the dm.dc_lock before detecting link.
Reviewed-by: Hersen Wu <hersen.wu@amd.com>
Acked-by: Solomon Chiu <solomon.chiu@amd.com>
Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -2756,10 +2756,13 @@ static int dm_resume(void *handle)
 		if (!dc_link_detect_sink(aconnector->dc_link, &new_connection_type))
 			DRM_ERROR("KMS: Failed to detect connector\n");
 
-		if (aconnector->base.force && new_connection_type == dc_connection_none)
+		if (aconnector->base.force && new_connection_type == dc_connection_none) {
 			emulated_link_detect(aconnector->dc_link);
-		else
+		} else {
+			mutex_lock(&dm->dc_lock);
 			dc_link_detect(aconnector->dc_link, DETECT_REASON_HPD);
+			mutex_unlock(&dm->dc_lock);
+		}
 
 		if (aconnector->fake_enable && aconnector->dc_link->local_sink)
 			aconnector->fake_enable = false;
@@ -3090,6 +3093,7 @@ static void handle_hpd_irq_helper(struct amdgpu_dm_connector *aconnector)
 #ifdef CONFIG_DRM_AMD_DC_HDCP
 	struct dm_connector_state *dm_con_state = to_dm_connector_state(connector->state);
 #endif
+	bool ret = false;
 
 	if (adev->dm.disable_hpd_irq)
 		return;
@@ -3121,8 +3125,11 @@ static void handle_hpd_irq_helper(struct amdgpu_dm_connector *aconnector)
 
 		if (aconnector->base.force == DRM_FORCE_UNSPECIFIED)
 			drm_kms_helper_connector_hotplug_event(connector);
-
-	} else if (dc_link_detect(aconnector->dc_link, DETECT_REASON_HPD)) {
+	} else {
+		mutex_lock(&adev->dm.dc_lock);
+		ret = dc_link_detect(aconnector->dc_link, DETECT_REASON_HPD);
+		mutex_unlock(&adev->dm.dc_lock);
+		if (ret) {
 			amdgpu_dm_update_connector_after_detect(aconnector);
 
 			drm_modeset_lock_all(dev);
@@ -3132,6 +3139,7 @@ static void handle_hpd_irq_helper(struct amdgpu_dm_connector *aconnector)
 			if (aconnector->base.force == DRM_FORCE_UNSPECIFIED)
 				drm_kms_helper_connector_hotplug_event(connector);
 		}
+	}
 	mutex_unlock(&aconnector->hpd_lock);
 
 }
@@ -3325,14 +3333,19 @@ static void handle_hpd_rx_irq(void *param)
 			drm_modeset_unlock_all(dev);
 
 			drm_kms_helper_connector_hotplug_event(connector);
-		} else if (dc_link_detect(dc_link, DETECT_REASON_HPDRX)) {
+		} else {
+			bool ret = false;
 
+			mutex_lock(&adev->dm.dc_lock);
+			ret = dc_link_detect(dc_link, DETECT_REASON_HPDRX);
+			mutex_unlock(&adev->dm.dc_lock);
+
+			if (ret) {
 				if (aconnector->fake_enable)
 					aconnector->fake_enable = false;
 
 				amdgpu_dm_update_connector_after_detect(aconnector);
 
-
 				drm_modeset_lock_all(dev);
 				dm_restore_drm_connector_state(dev, connector);
 				drm_modeset_unlock_all(dev);
@@ -3340,6 +3353,7 @@ static void handle_hpd_rx_irq(void *param)
 				drm_kms_helper_connector_hotplug_event(connector);
 			}
 		}
+	}
 #ifdef CONFIG_DRM_AMD_DC_HDCP
 	if (hpd_irq_data.bytes.device_service_irq.bits.CP_IRQ) {
 		if (adev->dm.hdcp_workqueue)
@@ -4342,12 +4356,20 @@ static int amdgpu_dm_initialize_drm_device(struct amdgpu_device *adev)
 		if (aconnector->base.force && new_connection_type == dc_connection_none) {
 			emulated_link_detect(link);
 			amdgpu_dm_update_connector_after_detect(aconnector);
+		} else {
+			bool ret = false;
+
+			mutex_lock(&dm->dc_lock);
+			ret = dc_link_detect(link, DETECT_REASON_BOOT);
+			mutex_unlock(&dm->dc_lock);
 
-		} else if (dc_link_detect(link, DETECT_REASON_BOOT)) {
+			if (ret) {
 				amdgpu_dm_update_connector_after_detect(aconnector);
 				register_backlight_device(dm, link);
+
 				if (dm->num_of_edps)
 					update_connector_ext_caps(aconnector);
+
 				if (psr_feature_enabled)
 					amdgpu_dm_set_psr_caps(link);
 
@@ -4357,8 +4379,7 @@ static int amdgpu_dm_initialize_drm_device(struct amdgpu_device *adev)
 				if (link->psr_settings.psr_feature_enabled)
 					adev_to_drm(adev)->vblank_disable_immediate = false;
 			}
-
-
+		}
 	}
 
 	/* Software is initialized. Now we can register interrupt handlers. */

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c

@@ -1239,12 +1239,14 @@ static ssize_t trigger_hotplug(struct file *f, const char __user *buf,
 	struct drm_connector *connector = &aconnector->base;
 	struct dc_link *link = NULL;
 	struct drm_device *dev = connector->dev;
+	struct amdgpu_device *adev = drm_to_adev(dev);
 	enum dc_connection_type new_connection_type = dc_connection_none;
 	char *wr_buf = NULL;
 	uint32_t wr_buf_size = 42;
 	int max_param_num = 1;
 	long param[1] = {0};
 	uint8_t param_nums = 0;
+	bool ret = false;
 
 	if (!aconnector || !aconnector->dc_link)
 		return -EINVAL;
@@ -1280,7 +1282,11 @@ static ssize_t trigger_hotplug(struct file *f, const char __user *buf,
 			new_connection_type != dc_connection_none)
 			goto unlock;
 
-		if (!dc_link_detect(aconnector->dc_link, DETECT_REASON_HPD))
+		mutex_lock(&adev->dm.dc_lock);
+		ret = dc_link_detect(aconnector->dc_link, DETECT_REASON_HPD);
+		mutex_unlock(&adev->dm.dc_lock);
+
+		if (!ret)
 			goto unlock;
 
 		amdgpu_dm_update_connector_after_detect(aconnector);
@@ -3302,7 +3308,10 @@ static int trigger_hpd_mst_set(void *data, u64 val)
 			aconnector = to_amdgpu_dm_connector(connector);
 			if (aconnector->dc_link->type == dc_connection_mst_branch &&
 			    aconnector->mst_mgr.aux) {
+				mutex_lock(&adev->dm.dc_lock);
 				dc_link_detect(aconnector->dc_link, DETECT_REASON_HPD);
+				mutex_unlock(&adev->dm.dc_lock);
+
 				drm_dp_mst_topology_mgr_set_mst(&aconnector->mst_mgr, true);
 			}
 		}