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, 5 insertions, 3 deletions

diff --git a/drivers/gpu/drm/nouveau/nouveau_connector.c b/drivers/gpu/drm/nouveau/nouveau_connector.c
index a1473fff06ac..67d515cb67e0 100644
--- a/drivers/gpu/drm/nouveau/nouveau_connector.c
+++ b/drivers/gpu/drm/nouveau/nouveau_connector.c
@@ -168,7 +168,8 @@ nouveau_connector_set_encoder(struct drm_connector *connector,
 }
 
 static enum drm_connector_status
-nouveau_connector_detect(struct drm_connector *connector)
+nouveau_connector_detect(struct drm_connector *connector,
+                         bool nondestructive)
 {
         struct drm_device *dev = connector->dev;
         struct nouveau_connector *nv_connector = nouveau_connector(connector);
@@ -246,7 +247,8 @@ detect_analog:
 }
 
 static enum drm_connector_status
-nouveau_connector_detect_lvds(struct drm_connector *connector)
+nouveau_connector_detect_lvds(struct drm_connector *connector,
+                              bool nondestructive)
 {
         struct drm_device *dev = connector->dev;
         struct drm_nouveau_private *dev_priv = dev->dev_private;
@@ -267,7 +269,7 @@ nouveau_connector_detect_lvds(struct drm_connector *connector)
 
         /* Try retrieving EDID via DDC */
         if (!dev_priv->vbios.fp_no_ddc) {
-                status = nouveau_connector_detect(connector);
+                status = nouveau_connector_detect(connector, nondestructive);
                 if (status == connector_status_connected)
                         goto out;
         }