[PATCH 11/21] drm/dp: Read eDP version from DPCD

[Thierry Reding]

From: Thierry Reding <treding at nvidia.com>

If the sink supports eDP, read the eDP revision from it's DPCD.

Signed-off-by: Thierry Reding <treding at nvidia.com>
---
 drivers/gpu/drm/drm_dp_helper.c | 16 +++++++++++++++-
 include/drm/drm_dp_helper.h     |  2 ++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index acab8dc48e2c..5b36e8e39ca7 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -382,6 +382,7 @@ 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;
@@ -418,9 +419,22 @@ int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link)
 	link->caps.fast_training = drm_dp_fast_training_cap(values);
 	link->caps.channel_coding = drm_dp_channel_coding_supported(values);
 
-	if (drm_dp_alternate_scrambler_reset_cap(values))
+	if (drm_dp_alternate_scrambler_reset_cap(values)) {
+		static const u8 edp_revs[] = { 0x11, 0x12, 0x13, 0x14 };
+		u8 value;
+
 		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(edp_revs))
+			DRM_ERROR("unsupported eDP version: %02x\n", value);
+		else
+			link->edp = edp_revs[value];
+	}
+
 	link->rate = link->max_rate;
 	link->lanes = link->max_lanes;
 
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index f9f65bc13df5..13c50e905205 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -1405,6 +1405,7 @@ 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
  */
@@ -1414,6 +1415,7 @@ struct drm_dp_link {
 	unsigned int max_lanes;
 
 	struct drm_dp_link_caps caps;
+	unsigned char edp;
 
 	unsigned int rate;
 	unsigned int lanes;
-- 
2.22.0