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>

12 files changed, 54 insertions, 26 deletions

diff --git a/drivers/gpu/drm/drm_crtc_helper.c b/drivers/gpu/drm/drm_crtc_helper.c
index de152a58967d..fb6b70fc6572 100644
--- a/drivers/gpu/drm/drm_crtc_helper.c
+++ b/drivers/gpu/drm/drm_crtc_helper.c
@@ -103,7 +103,7 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
                 if (connector->funcs->force)
                         connector->funcs->force(connector);
         } else {
-                connector->status = connector->funcs->detect(connector);
+                connector->status = connector->funcs->detect(connector, false);
                 drm_kms_helper_poll_enable(dev);
         }
 
@@ -866,7 +866,7 @@ static void output_poll_execute(struct work_struct *work)
                     !(connector->polled & DRM_CONNECTOR_POLL_HPD))
                         continue;
 
-                status = connector->funcs->detect(connector);
+                status = connector->funcs->detect(connector, true);
                 if (old_status != status)
                         changed = true;
         }
diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c
index 86118a742231..85da4c40694c 100644
--- a/drivers/gpu/drm/drm_sysfs.c
+++ b/drivers/gpu/drm/drm_sysfs.c
@@ -159,7 +159,7 @@ static ssize_t status_show(struct device *device,
         struct drm_connector *connector = to_drm_connector(device);
         enum drm_connector_status status;
 
-        status = connector->funcs->detect(connector);
+        status = connector->funcs->detect(connector, true);
         return snprintf(buf, PAGE_SIZE, "%s\n",
                         drm_get_connector_status_name(status));
 }
diff --git a/drivers/gpu/drm/i915/intel_crt.c b/drivers/gpu/drm/i915/intel_crt.c
index 4b7735196cd5..0350e5d711f8 100644
--- a/drivers/gpu/drm/i915/intel_crt.c
+++ b/drivers/gpu/drm/i915/intel_crt.c
@@ -400,7 +400,9 @@ intel_crt_load_detect(struct drm_crtc *crtc, struct intel_encoder *intel_encoder
         return status;
 }
 
-static enum drm_connector_status intel_crt_detect(struct drm_connector *connector)
+static enum drm_connector_status
+intel_crt_detect(struct drm_connector *connector,
+                 bool nondestructive)
 {
         struct drm_device *dev = connector->dev;
         struct drm_encoder *encoder = intel_attached_encoder(connector);
@@ -419,6 +421,9 @@ static enum drm_connector_status intel_crt_detect(struct drm_connector *connecto
         if (intel_crt_detect_ddc(encoder))
                 return connector_status_connected;
 
+        if (nondestructive)
+                return connector->status;
+
         /* for pre-945g platforms use load detect */
         if (encoder->crtc && encoder->crtc->enabled) {
                 status = intel_crt_load_detect(encoder->crtc, intel_encoder);
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 51d142939a26..e1a2a05fb838 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1386,7 +1386,8 @@ ironlake_dp_detect(struct drm_connector *connector)
  * \return false if DP port is disconnected.
  */
 static enum drm_connector_status
-intel_dp_detect(struct drm_connector *connector)
+intel_dp_detect(struct drm_connector *connector,
+                bool nondestructive)
 {
         struct drm_encoder *encoder = intel_attached_encoder(connector);
         struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
diff --git a/drivers/gpu/drm/i915/intel_dvo.c b/drivers/gpu/drm/i915/intel_dvo.c
index a399f4b2c1c5..f0de1addf8a4 100644
--- a/drivers/gpu/drm/i915/intel_dvo.c
+++ b/drivers/gpu/drm/i915/intel_dvo.c
@@ -221,7 +221,9 @@ static void intel_dvo_mode_set(struct drm_encoder *encoder,
  *
  * Unimplemented.
  */
-static enum drm_connector_status intel_dvo_detect(struct drm_connector *connector)
+static enum drm_connector_status
+intel_dvo_detect(struct drm_connector *connector,
+                 bool nondestructive)
 {
         struct drm_encoder *encoder = intel_attached_encoder(connector);
         struct intel_dvo *intel_dvo = enc_to_intel_dvo(encoder);
diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
index ccd4c97e6524..2ea123d8d22b 100644
--- a/drivers/gpu/drm/i915/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/intel_hdmi.c
@@ -139,7 +139,8 @@ static bool intel_hdmi_mode_fixup(struct drm_encoder *encoder,
 }
 
 static enum drm_connector_status
-intel_hdmi_detect(struct drm_connector *connector)
+intel_hdmi_detect(struct drm_connector *connector,
+                  bool nondestructive)
 {
         struct drm_encoder *encoder = intel_attached_encoder(connector);
         struct intel_hdmi *intel_hdmi = enc_to_intel_hdmi(encoder);
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;
diff --git a/drivers/gpu/drm/i915/intel_sdvo.c b/drivers/gpu/drm/i915/intel_sdvo.c
index e3b7a7ee39cb..db6b6d4b8fae 100644
--- a/drivers/gpu/drm/i915/intel_sdvo.c
+++ b/drivers/gpu/drm/i915/intel_sdvo.c
@@ -1417,7 +1417,7 @@ intel_analog_is_connected(struct drm_device *dev)
         if (!analog_connector)
                 return false;
 
-        if (analog_connector->funcs->detect(analog_connector) ==
+        if (analog_connector->funcs->detect(analog_connector, true) ==
                         connector_status_disconnected)
                 return false;
 
@@ -1486,7 +1486,9 @@ intel_sdvo_hdmi_sink_detect(struct drm_connector *connector)
         return status;
 }
 
-static enum drm_connector_status intel_sdvo_detect(struct drm_connector *connector)
+static enum drm_connector_status
+intel_sdvo_detect(struct drm_connector *connector,
+                  bool nondestructive)
 {
         uint16_t response;