drm/amd/display: fix access hdcp_workqueue assert

[Why] hdcp are enabled for asics from raven. for old asics
which hdcp are not enabled, hdcp_workqueue are null. some
access to hdcp work queue are not guarded with pointer check.

[How] add hdcp_workqueue pointer check before access workqueue.

Fixes: 82986fd6 ("drm/amd/display: save restore hdcp state when display is unplugged from mst hub")
Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2444Reported-by: Niklāvs Koļesņikovs <89q1r14hd@relay.firefox.com>
Reviewed-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Hersen Wu <hersenxs.wu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

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

@@ -8559,6 +8559,9 @@ static void amdgpu_dm_atomic_commit_tail(struct drm_atomic_state *state)
 		struct amdgpu_crtc *acrtc = to_amdgpu_crtc(dm_new_con_state->base.crtc);
 		struct amdgpu_dm_connector *aconnector = to_amdgpu_dm_connector(connector);
 
+		if (!adev->dm.hdcp_workqueue)
+			continue;
+
 		pr_debug("[HDCP_DM] -------------- i : %x ----------\n", i);
 
 		if (!connector)
@@ -8607,6 +8610,9 @@ static void amdgpu_dm_atomic_commit_tail(struct drm_atomic_state *state)
 		struct amdgpu_crtc *acrtc = to_amdgpu_crtc(dm_new_con_state->base.crtc);
 		struct amdgpu_dm_connector *aconnector = to_amdgpu_dm_connector(connector);
 
+		if (!adev->dm.hdcp_workqueue)
+			continue;
+
 		new_crtc_state = NULL;
 		old_crtc_state = NULL;
 

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

@@ -379,13 +379,17 @@ static int dm_dp_mst_get_modes(struct drm_connector *connector)
 		if (aconnector->dc_sink && connector->state) {
 			struct drm_device *dev = connector->dev;
 			struct amdgpu_device *adev = drm_to_adev(dev);
-			struct hdcp_workqueue *hdcp_work = adev->dm.hdcp_workqueue;
-			struct hdcp_workqueue *hdcp_w = &hdcp_work[aconnector->dc_link->link_index];
 
-			connector->state->hdcp_content_type =
-			hdcp_w->hdcp_content_type[connector->index];
-			connector->state->content_protection =
-			hdcp_w->content_protection[connector->index];
+			if (adev->dm.hdcp_workqueue) {
+				struct hdcp_workqueue *hdcp_work = adev->dm.hdcp_workqueue;
+				struct hdcp_workqueue *hdcp_w =
+					&hdcp_work[aconnector->dc_link->link_index];
+
+				connector->state->hdcp_content_type =
+				hdcp_w->hdcp_content_type[connector->index];
+				connector->state->content_protection =
+				hdcp_w->content_protection[connector->index];
+			}
 		}
 
 		if (aconnector->dc_sink) {