drm/i915/dp: Extract drm_dp_read_sink_count_cap()

Since other drivers are also going to need to be aware of the sink count
in order to do proper dongle detection, we might as well steal i915's
DP_SINK_COUNT helpers and move them into DRM helpers so that other
dirvers can use them as well.

Note that this also starts using intel_dp_has_sink_count() in
intel_dp_detect_dpcd(), which is a functional change.

v5:
* Change name from drm_dp_has_sink_count() to
  drm_dp_read_sink_count_cap()

Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Sean Paul <sean@poorly.run>
Link: https://patchwork.freedesktop.org/patch/msgid/20200826182456.322681-16-lyude@redhat.com

drivers/gpu/drm/drm_dp_helper.c

@@ -726,6 +726,28 @@ void drm_dp_set_subconnector_property(struct drm_connector *connector,
 }
 EXPORT_SYMBOL(drm_dp_set_subconnector_property);
 
+/**
+ * drm_dp_read_sink_count_cap() - Check whether a given connector has a valid sink
+ * count
+ * @connector: The DRM connector to check
+ * @dpcd: A cached copy of the connector's DPCD RX capabilities
+ * @desc: A cached copy of the connector's DP descriptor
+ *
+ * Returns: %True if the (e)DP connector has a valid sink count that should
+ * be probed, %false otherwise.
+ */
+bool drm_dp_read_sink_count_cap(struct drm_connector *connector,
+				const u8 dpcd[DP_RECEIVER_CAP_SIZE],
+				const struct drm_dp_desc *desc)
+{
+	/* Some eDP panels don't set a valid value for the sink count */
+	return connector->connector_type != DRM_MODE_CONNECTOR_eDP &&
+		dpcd[DP_DPCD_REV] >= DP_DPCD_REV_11 &&
+		dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_PRESENT &&
+		!drm_dp_has_quirk(desc, 0, DP_DPCD_QUIRK_NO_SINK_COUNT);
+}
+EXPORT_SYMBOL(drm_dp_read_sink_count_cap);
+
 /*
  * I2C-over-AUX implementation
  */

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

@@ -4634,6 +4634,16 @@ intel_edp_init_dpcd(struct intel_dp *intel_dp)
 	return true;
 }
 
+static bool
+intel_dp_has_sink_count(struct intel_dp *intel_dp)
+{
+	if (!intel_dp->attached_connector)
+		return false;
+
+	return drm_dp_read_sink_count_cap(&intel_dp->attached_connector->base,
+					  intel_dp->dpcd,
+					  &intel_dp->desc);
+}
 
 static bool
 intel_dp_get_dpcd(struct intel_dp *intel_dp)
@@ -4653,13 +4663,7 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
 		intel_dp_set_common_rates(intel_dp);
 	}
 
-	/*
+	if (intel_dp_has_sink_count(intel_dp)) {
-	 * Some eDP panels do not set a valid value for sink count, that is why
-	 * it don't care about read it here and in intel_edp_init_dpcd().
-	 */
-	if (!intel_dp_is_edp(intel_dp) &&
-	    !drm_dp_has_quirk(&intel_dp->desc, 0,
-			      DP_DPCD_QUIRK_NO_SINK_COUNT)) {
 		u8 count;
 		ssize_t r;
 
@@ -5939,9 +5943,8 @@ intel_dp_detect_dpcd(struct intel_dp *intel_dp)
 		return connector_status_connected;
 
 	/* If we're HPD-aware, SINK_COUNT changes dynamically */
-	if (intel_dp->dpcd[DP_DPCD_REV] >= 0x11 &&
+	if (intel_dp_has_sink_count(intel_dp) &&
 	    intel_dp->downstream_ports[0] & DP_DS_PORT_HPD) {
-
 		return intel_dp->sink_count ?
 		connector_status_connected : connector_status_disconnected;
 	}

include/drm/drm_dp_helper.h

@@ -1631,6 +1631,11 @@ void drm_dp_set_subconnector_property(struct drm_connector *connector,
 				      const u8 *dpcd,
 				      const u8 port_cap[4]);
 
+struct drm_dp_desc;
+bool drm_dp_read_sink_count_cap(struct drm_connector *connector,
+				const u8 dpcd[DP_RECEIVER_CAP_SIZE],
+				const struct drm_dp_desc *desc);
+
 void drm_dp_remote_aux_init(struct drm_dp_aux *aux);
 void drm_dp_aux_init(struct drm_dp_aux *aux);
 int drm_dp_aux_register(struct drm_dp_aux *aux);
@@ -1689,7 +1694,8 @@ enum drm_dp_quirk {
 	 * @DP_DPCD_QUIRK_NO_SINK_COUNT:
 	 *
 	 * The device does not set SINK_COUNT to a non-zero value.
-	 * The driver should ignore SINK_COUNT during detection.
+	 * The driver should ignore SINK_COUNT during detection. Note that
+	 * drm_dp_read_sink_count_cap() automatically checks for this quirk.
 	 */
 	DP_DPCD_QUIRK_NO_SINK_COUNT,
 	/**