drm/i915: Read DSC capabilities of the HDMI2.1 PCON encoder

This patch adds support to read and store the DSC capabilities of the
HDMI2.1 PCon encoder. It also adds a new field to store these caps,
The caps are read during dfp update and can later be used to get the
PPS parameters for PCON-HDMI2.1 sink pair. Which inturn will be used
to take a call to override the existing PPS-metadata, by either
writing the entire new PPS metadata, or by writing only the
PPS override parameters.

v2: Restructured the code to read all capability DPCDs at once and store
in an array in intel_dp structure.

v3: rebase
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
[Jani: Fixed checkpatch PARENTHESIS_ALIGNMENT.]
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201218103723.30844-13-ankit.k.nautiyal@intel.com

drivers/gpu/drm/i915/display/intel_display_types.h

@@ -1344,6 +1344,7 @@ struct intel_dp {
 	u8 lttpr_common_caps[DP_LTTPR_COMMON_CAP_SIZE];
 	u8 lttpr_phy_caps[DP_MAX_LTTPR_COUNT][DP_LTTPR_PHY_CAP_SIZE];
 	u8 fec_capable;
+	u8 pcon_dsc_dpcd[DP_PCON_DSC_ENCODER_CAP_SIZE];
 	/* source rates */
 	int num_source_rates;
 	const int *source_rates;

drivers/gpu/drm/i915/display/intel_dp.c

@@ -3976,6 +3976,24 @@ cpt_set_link_train(struct intel_dp *intel_dp,
 	intel_de_posting_read(dev_priv, intel_dp->output_reg);
 }
 
+static void intel_dp_get_pcon_dsc_cap(struct intel_dp *intel_dp)
+{
+	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+
+	/* Clear the cached register set to avoid using stale values */
+
+	memset(intel_dp->pcon_dsc_dpcd, 0, sizeof(intel_dp->pcon_dsc_dpcd));
+
+	if (drm_dp_dpcd_read(&intel_dp->aux, DP_PCON_DSC_ENCODER,
+			     intel_dp->pcon_dsc_dpcd,
+			     sizeof(intel_dp->pcon_dsc_dpcd)) < 0)
+		drm_err(&i915->drm, "Failed to read DPCD register 0x%x\n",
+			DP_PCON_DSC_ENCODER);
+
+	drm_dbg_kms(&i915->drm, "PCON ENCODER DSC DPCD: %*ph\n",
+		    (int)sizeof(intel_dp->pcon_dsc_dpcd), intel_dp->pcon_dsc_dpcd);
+}
+
 static int intel_dp_pcon_get_frl_mask(u8 frl_bw_mask)
 {
 	int bw_gbps[] = {9, 18, 24, 32, 40, 48};
@@ -6708,6 +6726,8 @@ intel_dp_update_dfp(struct intel_dp *intel_dp,
 		    intel_dp->dfp.min_tmds_clock,
 		    intel_dp->dfp.max_tmds_clock,
 		    intel_dp->dfp.pcon_max_frl_bw);
+
+	intel_dp_get_pcon_dsc_cap(intel_dp);
 }
 
 static void