[PATCH v7 4/5] drm: Update bits per component for display info

[Mika Kahola]

DisplayPort branch device may define max supported bits per
component. Update display info based on this value if bpc
is defined.

v2: cleanup to match the drm_dp_helper.c patches introduced
    earlier in this series
v3: Fill bpc for connector's display info in separate
    drm_dp_helper function (Daniel)

Signed-off-by: Mika Kahola <mika.kahola at intel.com>
---
 drivers/gpu/drm/drm_dp_helper.c | 24 ++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_dp.c |  3 +++
 include/drm/drm_dp_helper.h     |  4 ++++
 3 files changed, 31 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 1f36016..a2c46ed 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -514,6 +514,30 @@ int drm_dp_downstream_max_bpc(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
 EXPORT_SYMBOL(drm_dp_downstream_max_bpc);
 
 /**
+ * drm_dp_downstream_update_max_bpc() - extract branch device max
+ *                                      bits per component and update
+ *                                      connector max bpc
+ * @dpcd: DisplayPort configuration data
+ * @port_cap: port capabilities
+ * @connector: Connector info
+ * Returns current max bpc on success
+ */
+int drm_dp_downstream_update_max_bpc(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
+				     const u8 port_cap[4],
+				     struct drm_connector *connector)
+{
+	if (dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_PRESENT) {
+		int bpc = drm_dp_downstream_max_bpc(dpcd, port_cap);
+
+		if (bpc > 0)
+			connector->display_info.bpc = bpc;
+	}
+
+	return connector->display_info.bpc;
+}
+EXPORT_SYMBOL(drm_dp_downstream_update_max_bpc);
+
+/**
  * drm_dp_downstream_hw_rev() - read DP branch device HW revision
  * @aux: DisplayPort AUX channel
  *
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index e990c8b..763e2f5 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -3985,6 +3985,9 @@ intel_dp_detect_dpcd(struct intel_dp *intel_dp)
 	uint8_t *dpcd = intel_dp->dpcd;
 	uint8_t type;
 
+	drm_dp_downstream_update_max_bpc(dpcd, intel_dp->downstream_ports,
+					 &intel_dp->attached_connector->base);
+
 	if (!intel_dp_get_dpcd(intel_dp))
 		return connector_status_disconnected;
 
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 45366aa..5491a9b 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -26,6 +26,7 @@
 #include <linux/types.h>
 #include <linux/i2c.h>
 #include <linux/delay.h>
+#include <drm/drm_crtc.h>
 
 /*
  * Unless otherwise noted, all values are from the DP 1.1a spec.  Note that
@@ -827,6 +828,9 @@ int drm_dp_downstream_max_clock(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
 				const u8 port_cap[4]);
 int drm_dp_downstream_max_bpc(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
 			      const u8 port_cap[4]);
+int drm_dp_downstream_update_max_bpc(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
+				     const u8 port_cap[4],
+				     struct drm_connector *connector);
 int drm_dp_downstream_id(struct drm_dp_aux *aux, char id[6]);
 int drm_dp_downstream_hw_rev(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
 			     struct drm_dp_aux *aux, struct drm_dp_link *link);
-- 
1.9.1