drm/i915: Parse DP/eDP max lane count from VBT

Limit the DP lane count based on the new VBT DP/eDP max
lane count field.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220715202044.11153-13-ville.syrjala@linux.intel.comReviewed-by: NJani Nikula <jani.nikula@intel.com>

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

@@ -2515,6 +2515,14 @@ static int _intel_bios_dp_max_link_rate(const struct intel_bios_encoder_data *de
 		return parse_bdb_216_dp_max_link_rate(devdata->child.dp_max_link_rate);
 }
 
+static int _intel_bios_dp_max_lane_count(const struct intel_bios_encoder_data *devdata)
+{
+	if (!devdata || devdata->i915->display.vbt.version < 244)
+		return 0;
+
+	return devdata->child.dp_max_lane_count + 1;
+}
+
 static void sanitize_device_type(struct intel_bios_encoder_data *devdata,
 				 enum port port)
 {
@@ -3696,6 +3704,14 @@ int intel_bios_dp_max_link_rate(struct intel_encoder *encoder)
 	return _intel_bios_dp_max_link_rate(devdata);
 }
 
+int intel_bios_dp_max_lane_count(struct intel_encoder *encoder)
+{
+	struct drm_i915_private *i915 = to_i915(encoder->base.dev);
+	const struct intel_bios_encoder_data *devdata = i915->display.vbt.ports[encoder->port];
+
+	return _intel_bios_dp_max_lane_count(devdata);
+}
+
 int intel_bios_alternate_ddc_pin(struct intel_encoder *encoder)
 {
 	struct drm_i915_private *i915 = to_i915(encoder->base.dev);

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

@@ -258,6 +258,7 @@ bool intel_bios_get_dsc_params(struct intel_encoder *encoder,
 int intel_bios_max_tmds_clock(struct intel_encoder *encoder);
 int intel_bios_hdmi_level_shift(struct intel_encoder *encoder);
 int intel_bios_dp_max_link_rate(struct intel_encoder *encoder);
+int intel_bios_dp_max_lane_count(struct intel_encoder *encoder);
 int intel_bios_alternate_ddc_pin(struct intel_encoder *encoder);
 bool intel_bios_port_supports_typec_usb(struct drm_i915_private *i915, enum port port);
 bool intel_bios_port_supports_tbt(struct drm_i915_private *i915, enum port port);

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

@@ -286,11 +286,22 @@ static int intel_dp_max_common_rate(struct intel_dp *intel_dp)
 	return intel_dp_common_rate(intel_dp, intel_dp->num_common_rates - 1);
 }
 
+static int intel_dp_max_source_lane_count(struct intel_digital_port *dig_port)
+{
+	int vbt_max_lanes = intel_bios_dp_max_lane_count(&dig_port->base);
+	int max_lanes = dig_port->max_lanes;
+
+	if (vbt_max_lanes)
+		max_lanes = min(max_lanes, vbt_max_lanes);
+
+	return max_lanes;
+}
+
 /* Theoretical max between source and sink */
 static int intel_dp_max_common_lane_count(struct intel_dp *intel_dp)
 {
 	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
-	int source_max = dig_port->max_lanes;
+	int source_max = intel_dp_max_source_lane_count(dig_port);
 	int sink_max = intel_dp->max_sink_lane_count;
 	int fia_max = intel_tc_port_fia_max_lane_count(dig_port);
 	int lttpr_max = drm_dp_lttpr_max_lane_count(intel_dp->lttpr_common_caps);