drm/probe-helper: clamp unknown connector status in the poll work

[firefly-linux-kernel-4.4.55.git] / drivers / gpu / drm / drm_probe_helper.c

diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
index 33bf550a1d3f54b4466fd0584ac7378205cee0c8..6591d48c1b9d0f3bcc4a74a8da730833cbc4e839 100644 (file)
--- a/drivers/gpu/drm/drm_probe_helper.c
+++ b/drivers/gpu/drm/drm_probe_helper.c
@@ -335,6 +335,24 @@ static void output_poll_execute(struct work_struct *work)
                if (old_status != connector->status) {
                        const char *old, *new;
 
+                       /*
+                        * The poll work sets force=false when calling detect so
+                        * that drivers can avoid to do disruptive tests (e.g.
+                        * when load detect cycles could cause flickering on
+                        * other, running displays). This bears the risk that we
+                        * flip-flop between unknown here in the poll work and
+                        * the real state when userspace forces a full detect
+                        * call after receiving a hotplug event due to this
+                        * change.
+                        *
+                        * Hence clamp an unknown detect status to the old
+                        * value.
+                        */
+                       if (connector->status == connector_status_unknown) {
+                               connector->status = old_status;
+                               continue;
+                       }
+
                        old = drm_get_connector_status_name(old_status);
                        new = drm_get_connector_status_name(connector->status);