drm/i915: Read the EDP DPCD and PSR Capability

v2: reuse of just created is_edp_psr and put it at right place.
v3: move is_edp_psr above intel_edp_disable
v4: remove parentheses. Noticed by Paulo.
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Shobhit Kumar <shobhit.kumar@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_dp.c

@@ -1364,6 +1364,12 @@ static void intel_dp_get_config(struct intel_encoder *encoder,
 	}
 }
 
+static bool is_edp_psr(struct intel_dp *intel_dp)
+{
+	return is_edp(intel_dp) &&
+		intel_dp->psr_dpcd[0] & DP_PSR_IS_SUPPORTED;
+}
+
 static void intel_disable_dp(struct intel_encoder *encoder)
 {
 	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
@@ -2277,6 +2283,13 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
 	if (intel_dp->dpcd[DP_DPCD_REV] == 0)
 		return false; /* DPCD not present */
 
+	/* Check if the panel supports PSR */
+	memset(intel_dp->psr_dpcd, 0, sizeof(intel_dp->psr_dpcd));
+	intel_dp_aux_native_read_retry(intel_dp, DP_PSR_SUPPORT,
+				       intel_dp->psr_dpcd,
+				       sizeof(intel_dp->psr_dpcd));
+	if (is_edp_psr(intel_dp))
+		DRM_DEBUG_KMS("Detected EDP PSR Panel.\n");
 	if (!(intel_dp->dpcd[DP_DOWNSTREAMPORT_PRESENT] &
 	      DP_DWN_STRM_PORT_PRESENT))
 		return true; /* native DP sink */

drivers/gpu/drm/i915/intel_drv.h

@@ -487,6 +487,7 @@ struct intel_dp {
 	uint8_t link_bw;
 	uint8_t lane_count;
 	uint8_t dpcd[DP_RECEIVER_CAP_SIZE];
+	uint8_t psr_dpcd[EDP_PSR_RECEIVER_CAP_SIZE];
 	uint8_t downstream_ports[DP_MAX_DOWNSTREAM_PORTS];
 	struct i2c_adapter adapter;
 	struct i2c_algo_dp_aux_data algo;