[PATCH] drm: ignore disconnected <-> unknown status changes

[Knut Petersen]

Only generate a hotplug event if the status changed
to / from connector_status_connected.

On some hardware the connector status is oscillating
between disconnected and unknown, and the hotplug
events mirroring these transitions cause screen
distortions. As the only reasonable action on such
a status change is to ignore it, it also is safe
not to genereate a hotplug event at all.

Needed for / tested on AOpen i915GMm-hfs mobo.

Signed-off-by: Knut Petersen <Knut_Petersen@xxxxxxxxxxx>
---
 drivers/gpu/drm/drm_crtc_helper.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/drivers/gpu/drm/drm_crtc_helper.c b/drivers/gpu/drm/drm_crtc_helper.c
index 3252e70..fb6160b 100644
--- a/drivers/gpu/drm/drm_crtc_helper.c
+++ b/drivers/gpu/drm/drm_crtc_helper.c
@@ -954,7 +954,11 @@ static void output_poll_execute(struct work_struct *work)
 			      connector->base.id,
 			      drm_get_connector_name(connector),
 			      old_status, connector->status);
-		if (old_status != connector->status)
+		/* changes are only relevant if previous or
+		    current status is connector_status_connected */
+		if (old_status != connector->status &&
+		    (old_status == connector_status_connected ||
+		    connector->status == connector_status_connected))
 			changed = true;
 	}
 
-- 
1.7.7


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