[PATCH 4.5 176/238] drm/radeon/mst: fix regression in lane/link handling.

[Greg Kroah-Hartman]

4.5-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dave Airlie <airlied@xxxxxxxxxx>

commit b36f7d26a7fdc0b07b1217368ee09bb8560269f8 upstream.

The function this used changed in
    092c96a8ab9d1bd60ada2ed385cc364ce084180e
    drm/radeon: fix dp link rate selection (v2)

However for MST we should just always train to the
max link/rate. Though we probably need to limit this
for future hw, in theory radeon won't support it.

This fixes my 30" monitor with MST enabled.

Signed-off-by: Dave Airlie <airlied@xxxxxxxxxx>
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/gpu/drm/radeon/radeon_dp_mst.c |   12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

--- a/drivers/gpu/drm/radeon/radeon_dp_mst.c
+++ b/drivers/gpu/drm/radeon/radeon_dp_mst.c
@@ -525,17 +525,9 @@ static bool radeon_mst_mode_fixup(struct
 	drm_mode_set_crtcinfo(adjusted_mode, 0);
 	{
 	  struct radeon_connector_atom_dig *dig_connector;
-	  int ret;
-
 	  dig_connector = mst_enc->connector->con_priv;
-	  ret = radeon_dp_get_dp_link_config(&mst_enc->connector->base,
-					     dig_connector->dpcd, adjusted_mode->clock,
-					     &dig_connector->dp_lane_count,
-					     &dig_connector->dp_clock);
-	  if (ret) {
-		  dig_connector->dp_lane_count = 0;
-		  dig_connector->dp_clock = 0;
-	  }
+	  dig_connector->dp_lane_count = drm_dp_max_lane_count(dig_connector->dpcd);
+	  dig_connector->dp_clock = drm_dp_max_link_rate(dig_connector->dpcd);
 	  DRM_DEBUG_KMS("dig clock %p %d %d\n", dig_connector,
 			dig_connector->dp_lane_count, dig_connector->dp_clock);
 	}