drm/amd/display: retry 3 times before successfully reading

DPCD Extended Receiver Capability Field

[Why]
1.dpcd extended receiver capability sometimes read fail,
  and corrupted data leads to sink caps is not correct.
2.sometimes sink reply ack with fewer data

[How]
  check the return value of core_link_read_dpcd,
  try to read again when failure happens

Signed-off-by: Xiaodong Yan <Xiaodong.Yan@amd.com>
Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Acked-by: Tony Cheng <Tony.Cheng@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
index d91df5e..4d1f8ac 100644 (file)
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
@@ -2371,11 +2371,22 @@ static bool retrieve_link_cap(struct dc_link *link)
                        dpcd_data[DP_TRAINING_AUX_RD_INTERVAL];
 
                if (aux_rd_interval.bits.EXT_RECIEVER_CAP_FIELD_PRESENT == 1) {
-                       core_link_read_dpcd(
+                       uint8_t ext_cap_data[16];
+
+                       memset(ext_cap_data, '\0', sizeof(ext_cap_data));
+                       for (i = 0; i < read_dpcd_retry_cnt; i++) {
+                               status = core_link_read_dpcd(
                                link,
                                DP_DP13_DPCD_REV,
-                               dpcd_data,
-                               sizeof(dpcd_data));
+                               ext_cap_data,
+                               sizeof(ext_cap_data));
+                               if (status == DC_OK) {
+                                       memcpy(dpcd_data, ext_cap_data, sizeof(dpcd_data));
+                                       break;
+                               }
+                       }
+                       if (status != DC_OK)
+                               dm_error("%s: Read extend caps data failed, use cap from dpcd 0.\n", __func__);
                }
        }