drm/i915/bios: store child device pointer in DDI port info

This allows us to avoid iterating the child devices in some cases.

Also replace the presence bit with child device being non-NULL, and set
the child device pointer last to allow us to take advantage of it in
follow-up work.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/ceccb75d637af3134d0328d67cbd6623932f94db.1559308269.git.jani.nikula@intel.com

drivers/gpu/drm/i915/i915_drv.h

@@ -834,6 +834,9 @@ struct i915_gem_mm {
 #define I915_ENGINE_WEDGED_TIMEOUT  (60 * HZ)  /* Reset but no recovery? */
 
 struct ddi_vbt_port_info {
+	/* Non-NULL if port present. */
+	const struct child_device_config *child;
+
 	int max_tmds_clock;
 
 	/*
@@ -844,7 +847,6 @@ struct ddi_vbt_port_info {
 #define HDMI_LEVEL_SHIFT_UNKNOWN	0xff
 	u8 hdmi_level_shift;
 
-	u8 present:1;
 	u8 supports_dvi:1;
 	u8 supports_hdmi:1;
 	u8 supports_dp:1;

drivers/gpu/drm/i915/intel_bios.c

@@ -1251,7 +1251,7 @@ static void sanitize_ddc_pin(struct drm_i915_private *dev_priv,
 	for (p = PORT_A; p < I915_MAX_PORTS; p++) {
 		struct ddi_vbt_port_info *i = &dev_priv->vbt.ddi_port_info[p];
 
-		if (p == port || !i->present ||
+		if (p == port || !i->child ||
 		    info->alternate_ddc_pin != i->alternate_ddc_pin)
 			continue;
 
@@ -1287,7 +1287,7 @@ static void sanitize_aux_ch(struct drm_i915_private *dev_priv,
 	for (p = PORT_A; p < I915_MAX_PORTS; p++) {
 		struct ddi_vbt_port_info *i = &dev_priv->vbt.ddi_port_info[p];
 
-		if (p == port || !i->present ||
+		if (p == port || !i->child ||
 		    info->alternate_aux_channel != i->alternate_aux_channel)
 			continue;
 
@@ -1395,14 +1395,12 @@ static void parse_ddi_port(struct drm_i915_private *dev_priv,
 
 	info = &dev_priv->vbt.ddi_port_info[port];
 
-	if (info->present) {
+	if (info->child) {
 		DRM_DEBUG_KMS("More than one child device for port %c in VBT, using the first.\n",
 			      port_name(port));
 		return;
 	}
 
-	info->present = true;
-
 	is_dvi = child->device_type & DEVICE_TYPE_TMDS_DVI_SIGNALING;
 	is_dp = child->device_type & DEVICE_TYPE_DISPLAYPORT_OUTPUT;
 	is_crt = child->device_type & DEVICE_TYPE_ANALOG_OUTPUT;
@@ -1530,6 +1528,8 @@ static void parse_ddi_port(struct drm_i915_private *dev_priv,
 		DRM_DEBUG_KMS("VBT DP max link rate for port %c: %d\n",
 			      port_name(port), info->dp_max_link_rate);
 	}
+
+	info->child = child;
 }
 
 static void parse_ddi_ports(struct drm_i915_private *dev_priv, u8 bdb_version)