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authorDaniel Vetter <daniel.vetter@ffwll.ch>2015-01-21 08:45:22 +0100
committerDaniel Vetter <daniel.vetter@ffwll.ch>2015-01-22 06:11:39 +0100
commitb7703726251191cd9f3ef3a80b2d9667901eec95 (patch)
parent162b6a57ac50eec236530a16c071ffa50e87362a (diff)
drm/probe-helper: clamp unknown connector status in the poll worktopic/core-stuff-2015-01-23
On some chipset we try to avoid possibly invasive output detection methods (like load detect which can cause flickering elsewhere) in the output poll work. Drivers could hence return unknown when a previous full ->detect call returned a different state. This change will generate a hotplug event, forcing userspace to do a full scan. This in turn updates the connector->status field so that we will _again_ get a state change when the hotplug work re-runs in 10 seconds. To avoid this ping-pong loop detect this situation and clamp the connector state to the old value. Patch is inspired by a patch from Knut Peterson. Knut's patch completely ignored connector state changes if either the old or new status was unknown, which seemed to be a bit too agressive to me. v2: Rebased onto the drm_probe_helper.c extraction. References: http://lists.freedesktop.org/archives/dri-devel/2012-August/025975.html Cc: Knut Petersen <Knut_Petersen@t-online.de> Cc: Alex Deucher <alexander.deucher@amd.com> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> Acked-by: Alex Deucher <alexander.deucher@amd.com> Cc: Rob Clark <robdclark@gmail.com> Reviewed-by: Rob Clark <robdclark@gmail.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
1 files changed, 18 insertions, 0 deletions
diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
index 33bf550a1d3f..6591d48c1b9d 100644
--- 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);

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