drm/tegra: dp: Read eDP version from DPCD

If the sink supports eDP, read the eDP revision from it's DPCD.
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/dp.c

@@ -5,9 +5,12 @@
  */
 
 #include <drm/drm_dp_helper.h>
+#include <drm/drm_print.h>
 
 #include "dp.h"
 
+static const u8 drm_dp_edp_revisions[] = { 0x11, 0x12, 0x13, 0x14 };
+
 static void drm_dp_link_caps_reset(struct drm_dp_link_caps *caps)
 {
 	caps->enhanced_framing = false;
@@ -37,6 +40,7 @@ static void drm_dp_link_reset(struct drm_dp_link *link)
 	link->max_lanes = 0;
 
 	drm_dp_link_caps_reset(&link->caps);
+	link->edp = 0;
 
 	link->rate = 0;
 	link->lanes = 0;
@@ -55,7 +59,7 @@ static void drm_dp_link_reset(struct drm_dp_link *link)
  */
 int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link)
 {
-	u8 dpcd[DP_RECEIVER_CAP_SIZE];
+	u8 dpcd[DP_RECEIVER_CAP_SIZE], value;
 	int err;
 
 	drm_dp_link_reset(link);
@@ -73,9 +77,19 @@ int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link)
 	link->caps.fast_training = drm_dp_fast_training_cap(dpcd);
 	link->caps.channel_coding = drm_dp_channel_coding_supported(dpcd);
 
-	if (drm_dp_alternate_scrambler_reset_cap(dpcd))
+	if (drm_dp_alternate_scrambler_reset_cap(dpcd)) {
 		link->caps.alternate_scrambler_reset = true;
 
+		err = drm_dp_dpcd_readb(aux, DP_EDP_DPCD_REV, &value);
+		if (err < 0)
+			return err;
+
+		if (value >= ARRAY_SIZE(drm_dp_edp_revisions))
+			DRM_ERROR("unsupported eDP version: %02x\n", value);
+		else
+			link->edp = drm_dp_edp_revisions[value];
+	}
+
 	link->rate = link->max_rate;
 	link->lanes = link->max_lanes;
 

drivers/gpu/drm/tegra/dp.h

@@ -60,6 +60,7 @@ void drm_dp_link_caps_copy(struct drm_dp_link_caps *dest,
  * @max_rate: maximum clock rate supported on the link
  * @max_lanes: maximum number of lanes supported on the link
  * @caps: capabilities supported on the link (see &drm_dp_link_caps)
+ * @edp: eDP revision (0x11: eDP 1.1, 0x12: eDP 1.2, ...)
  * @rate: currently configured link rate
  * @lanes: currently configured number of lanes
  */
@@ -69,6 +70,7 @@ struct drm_dp_link {
 	unsigned int max_lanes;
 
 	struct drm_dp_link_caps caps;
+	unsigned char edp;
 
 	unsigned int rate;
 	unsigned int lanes;