drm/i915/dp: limit DP link rate based on VBT on CNL+

We have the max DP link rate info available in VBT since BDB version
216, included in child device config since commit c4fb60b9
("drm/i915/bios: add DP max link rate to VBT child device
struct"). Parse it and use it.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/a8b1364d1f2394fba3062b6ad11b474744ea4366.1517482774.git.jani.nikula@intel.com

drivers/gpu/drm/i915/i915_drv.h

@@ -1282,6 +1282,7 @@ struct ddi_vbt_port_info {
 
 	uint8_t dp_boost_level;
 	uint8_t hdmi_boost_level;
+	int dp_max_link_rate;		/* 0 for not limited by VBT */
 };
 
 enum psr_lines_to_wait {

drivers/gpu/drm/i915/intel_bios.c

@@ -1274,6 +1274,27 @@ static void parse_ddi_port(struct drm_i915_private *dev_priv, enum port port,
 		DRM_DEBUG_KMS("VBT HDMI boost level for port %c: %d\n",
 			      port_name(port), info->hdmi_boost_level);
 	}
+
+	/* DP max link rate for CNL+ */
+	if (bdb_version >= 216) {
+		switch (child->dp_max_link_rate) {
+		default:
+		case VBT_DP_MAX_LINK_RATE_HBR3:
+			info->dp_max_link_rate = 810000;
+			break;
+		case VBT_DP_MAX_LINK_RATE_HBR2:
+			info->dp_max_link_rate = 540000;
+			break;
+		case VBT_DP_MAX_LINK_RATE_HBR:
+			info->dp_max_link_rate = 270000;
+			break;
+		case VBT_DP_MAX_LINK_RATE_LBR:
+			info->dp_max_link_rate = 162000;
+			break;
+		}
+		DRM_DEBUG_KMS("VBT DP max link rate for port %c: %d\n",
+			      port_name(port), info->dp_max_link_rate);
+	}
 }
 
 static void parse_ddi_ports(struct drm_i915_private *dev_priv, u8 bdb_version)

drivers/gpu/drm/i915/intel_dp.c

@@ -268,8 +268,10 @@ intel_dp_set_source_rates(struct intel_dp *intel_dp)
 {
 	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
 	struct drm_i915_private *dev_priv = to_i915(dig_port->base.base.dev);
+	const struct ddi_vbt_port_info *info =
+		&dev_priv->vbt.ddi_port_info[dig_port->base.port];
 	const int *source_rates;
-	int size, max_rate = 0;
+	int size, max_rate = 0, vbt_max_rate = info->dp_max_link_rate;
 
 	/* This should only be done once */
 	WARN_ON(intel_dp->source_rates || intel_dp->num_source_rates);
@@ -293,6 +295,11 @@ intel_dp_set_source_rates(struct intel_dp *intel_dp)
 		size = ARRAY_SIZE(default_rates) - 1;
 	}
 
+	if (max_rate && vbt_max_rate)
+		max_rate = min(max_rate, vbt_max_rate);
+	else if (vbt_max_rate)
+		max_rate = vbt_max_rate;
+
 	if (max_rate)
 		size = intel_dp_rate_limit_len(source_rates, size, max_rate);
 

drivers/gpu/drm/i915/intel_vbt_defs.h

@@ -320,6 +320,11 @@ enum vbt_gmbus_ddi {
 	DDC_BUS_DDI_F,
 };
 
+#define VBT_DP_MAX_LINK_RATE_HBR3	0
+#define VBT_DP_MAX_LINK_RATE_HBR2	1
+#define VBT_DP_MAX_LINK_RATE_HBR	2
+#define VBT_DP_MAX_LINK_RATE_LBR	3
+
 /*
  * The child device config, aka the display device data structure, provides a
  * description of a port and its configuration on the platform.