drm/nouveau/drm/nouveau: Grab runtime PM ref in nv50_mstc_detect()

While we currently grab a runtime PM ref in nouveau's normal connector
detection code, we apparently don't do this for MST. This means if we're
in a scenario where the GPU is suspended and userspace attempts to do a
connector probe on an MSTC connector, the probe will fail entirely due
to the DP aux channel and GPU not being woken up:

[  316.633489] nouveau 0000:01:00.0: i2c: aux 000a: begin idle timeout ffffffff
[  316.635713] nouveau 0000:01:00.0: i2c: aux 000a: begin idle timeout ffffffff
[  316.637785] nouveau 0000:01:00.0: i2c: aux 000a: begin idle timeout ffffffff
...

So, grab a runtime PM ref here.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: stable@vger.kernel.org
Reviewed-by: Karol Herbst <kherbst@redhat.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

1 files changed, 14 insertions, 1 deletions

diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c
index 5691dfa1db6f..041e7daf8a33 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
@@ -900,9 +900,22 @@ static enum drm_connector_status
 nv50_mstc_detect(struct drm_connector *connector, bool force)
 {
         struct nv50_mstc *mstc = nv50_mstc(connector);
+        enum drm_connector_status conn_status;
+        int ret;
+
         if (!mstc->port)
                 return connector_status_disconnected;
-        return drm_dp_mst_detect_port(connector, mstc->port->mgr, mstc->port);
+
+        ret = pm_runtime_get_sync(connector->dev->dev);
+        if (ret < 0 && ret != -EACCES)
+                return connector_status_disconnected;
+
+        conn_status = drm_dp_mst_detect_port(connector, mstc->port->mgr,
+                                             mstc->port);
+
+        pm_runtime_mark_last_busy(connector->dev->dev);
+        pm_runtime_put_autosuspend(connector->dev->dev);
+        return conn_status;
 }
 
 static void