drm: Use a nondestructive mode for output detect when polling

Destructive load-detection is very expensive and due to failings
elsewhere can trigger system wide stalls of up to 600ms. A simple
first step to correcting this is not to invoke such an expensive
and destructive load-detection operation automatically.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=29536
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=16265
Reported-by: Bruno Prémont <bonbons@linux-vserver.org>
Tested-by: Sitsofe Wheeler <sitsofe@yahoo.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: stable@kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/intel_lvds.c b/drivers/gpu/drm/i915/intel_lvds.c
index 4fbb0165b26f..fb1bed8f4071 100644
--- a/drivers/gpu/drm/i915/intel_lvds.c
+++ b/drivers/gpu/drm/i915/intel_lvds.c
@@ -445,7 +445,9 @@ static void intel_lvds_mode_set(struct drm_encoder *encoder,
  * connected and closed means disconnected.  We also send hotplug events as
  * needed, using lid status notification from the input layer.
  */
-static enum drm_connector_status intel_lvds_detect(struct drm_connector *connector)
+static enum drm_connector_status
+intel_lvds_detect(struct drm_connector *connector,
+                  bool nondestructive)
 {
         struct drm_device *dev = connector->dev;
         enum drm_connector_status status = connector_status_connected;
@@ -540,7 +542,9 @@ static int intel_lid_notify(struct notifier_block *nb, unsigned long val,
          * the LID nofication event.
          */
         if (connector)
-                connector->status = connector->funcs->detect(connector);
+                connector->status = connector->funcs->detect(connector,
+                                                             true);
+
         /* Don't force modeset on machines where it causes a GPU lockup */
         if (dmi_check_system(intel_no_modeset_on_lid))
                 return NOTIFY_OK;