Merge remote-tracking branches 'asoc/topic/ac97', 'asoc/topic/ac97-mfd', 'asoc/topic...

[mirror_ubuntu-focal-kernel.git] / drivers / gpu / drm / i915 / intel_dp.c

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 203198659ab2dbfe788531dd60878efbd61c303e..09f274419eea1c7466b2ff6b846b4cc41aeae3d0 100644 (file)
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -3731,9 +3731,16 @@ intel_edp_init_dpcd(struct intel_dp *intel_dp)
 
        }
 
-       /* Read the eDP Display control capabilities registers */
-       if ((intel_dp->dpcd[DP_EDP_CONFIGURATION_CAP] & DP_DPCD_DISPLAY_CONTROL_CAPABLE) &&
-           drm_dp_dpcd_read(&intel_dp->aux, DP_EDP_DPCD_REV,
+       /*
+        * Read the eDP display control registers.
+        *
+        * Do this independent of DP_DPCD_DISPLAY_CONTROL_CAPABLE bit in
+        * DP_EDP_CONFIGURATION_CAP, because some buggy displays do not have it
+        * set, but require eDP 1.4+ detection (e.g. for supported link rates
+        * method). The display control registers should read zero if they're
+        * not supported anyway.
+        */
+       if (drm_dp_dpcd_read(&intel_dp->aux, DP_EDP_DPCD_REV,
                             intel_dp->edp_dpcd, sizeof(intel_dp->edp_dpcd)) ==
                             sizeof(intel_dp->edp_dpcd))
                DRM_DEBUG_KMS("EDP DPCD : %*ph\n", (int) sizeof(intel_dp->edp_dpcd),