[PATCH] drm/i915/dp: Add a meaningful return to intel_dp_read_dsc_dpcd

[Suraj Kandpal <suraj.kandpal@intel.com>]

Add a meaningful return to intel_dp_read_dsc_dpcd so tha we avoid
unwanted DPCD reads which are not needed once we know DSC DPCD
read fails. While we are at it remove the drm_err since we do not
shout error during intel_dp_detect phase since it may take time
to come up after pps_on is called for eDP scenario.

Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 79fd3b8d8b25..d2ed8ec145a2 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -4281,20 +4281,21 @@ static bool intel_dp_get_colorimetry_status(struct intel_dp *intel_dp)
 	return dprx & DP_VSC_SDP_EXT_FOR_COLORIMETRY_SUPPORTED;
 }
 
-static void intel_dp_read_dsc_dpcd(struct drm_dp_aux *aux,
-				   u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE])
+static int intel_dp_read_dsc_dpcd(struct drm_dp_aux *aux,
+				  u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE])
 {
 	if (drm_dp_dpcd_read(aux, DP_DSC_SUPPORT, dsc_dpcd,
 			     DP_DSC_RECEIVER_CAP_SIZE) < 0) {
-		drm_err(aux->drm_dev,
-			"Failed to read DPCD register 0x%x\n",
-			DP_DSC_SUPPORT);
-		return;
+		drm_dbg_kms(aux->drm_dev,
+			    "Could not read DSC DPCD register 0x%x\n",
+			    DP_DSC_SUPPORT);
+		return -EINVAL;
 	}
 
 	drm_dbg_kms(aux->drm_dev, "DSC DPCD: %*ph\n",
 		    DP_DSC_RECEIVER_CAP_SIZE,
 		    dsc_dpcd);
+	return 0;
 }
 
 static void init_dsc_overall_throughput_limits(struct intel_connector *connector, bool is_branch)
@@ -4345,8 +4346,11 @@ void intel_dp_get_dsc_sink_cap(u8 dpcd_rev,
 	if (dpcd_rev < DP_DPCD_REV_14)
 		return;
 
-	intel_dp_read_dsc_dpcd(connector->dp.dsc_decompression_aux,
-			       connector->dp.dsc_dpcd);
+	if (intel_dp_read_dsc_dpcd(connector->dp.dsc_decompression_aux,
+				   connector->dp.dsc_dpcd) < 0) {
+		drm_err(display->drm, "Failed to read DSC DPCD register\n");
+		return;
+	}
 
 	if (drm_dp_dpcd_readb(connector->dp.dsc_decompression_aux, DP_FEC_CAPABILITY,
 			      &connector->dp.fec_capability) < 0) {
@@ -4376,7 +4380,9 @@ static void intel_edp_get_dsc_sink_cap(u8 edp_dpcd_rev, struct intel_connector *
 	if (edp_dpcd_rev < DP_EDP_14)
 		return;
 
-	intel_dp_read_dsc_dpcd(connector->dp.dsc_decompression_aux, connector->dp.dsc_dpcd);
+	if (intel_dp_read_dsc_dpcd(connector->dp.dsc_decompression_aux,
+				   connector->dp.dsc_dpcd) < 0)
+		return;
 
 	if (connector->dp.dsc_dpcd[0] & DP_DSC_DECOMPRESSION_IS_SUPPORTED)
 		init_dsc_overall_throughput_limits(connector, false);
-- 
2.34.1