[PATCH 09/21] drm/dp: Read channel coding capability from sink

[Thierry Reding <thierry.reding@xxxxxxxxx>]

From: Thierry Reding <treding@xxxxxxxxxx>

Parse from the sink capabilities whether or not it supports ANSI 8B/10B
channel coding as specified in ANSI X3.230-1994, clause 11.

Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
---
 drivers/gpu/drm/drm_dp_helper.c | 3 +++
 include/drm/drm_dp_helper.h     | 9 +++++++++
 2 files changed, 12 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index c47d78973c1e..1c238196c8b4 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -357,6 +357,7 @@ static void drm_dp_link_caps_reset(struct drm_dp_link_caps *caps)
 	caps->enhanced_framing = false;
 	caps->tps3_supported = false;
 	caps->fast_training = false;
+	caps->channel_coding = false;
 }
 
 void drm_dp_link_caps_copy(struct drm_dp_link_caps *dest,
@@ -365,6 +366,7 @@ void drm_dp_link_caps_copy(struct drm_dp_link_caps *dest,
 	dest->enhanced_framing = src->enhanced_framing;
 	dest->tps3_supported = src->tps3_supported;
 	dest->fast_training = src->fast_training;
+	dest->channel_coding = src->channel_coding;
 }
 EXPORT_SYMBOL(drm_dp_link_caps_copy);
 
@@ -412,6 +414,7 @@ int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link)
 	link->caps.enhanced_framing = drm_dp_enhanced_frame_cap(values);
 	link->caps.tps3_supported = drm_dp_tps3_supported(values);
 	link->caps.fast_training = drm_dp_fast_training_cap(values);
+	link->caps.channel_coding = drm_dp_channel_coding_supported(values);
 
 	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 ab98ebb302a9..d144d3a54dbc 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -95,6 +95,7 @@
 # define DP_DETAILED_CAP_INFO_AVAILABLE	    (1 << 4) /* DPI */
 
 #define DP_MAIN_LINK_CHANNEL_CODING         0x006
+# define DP_CAP_ANSI_8B10B		    (1 << 0)
 
 #define DP_DOWN_STREAM_PORT_COUNT	    0x007
 # define DP_PORT_COUNT_MASK		    0x0f
@@ -1215,6 +1216,12 @@ drm_dp_sink_supports_fec(const u8 fec_capable)
 	return fec_capable & DP_FEC_CAPABLE;
 }
 
+static inline bool
+drm_dp_channel_coding_supported(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
+{
+	return dpcd[DP_MAIN_LINK_CHANNEL_CODING] & DP_CAP_ANSI_8B10B;
+}
+
 /*
  * DisplayPort AUX channel
  */
@@ -1371,11 +1378,13 @@ int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux,
  * @enhanced_framing: enhanced framing capability (mandatory as of DP 1.2)
  * @tps3_supported: training pattern sequence 3 supported for equalization
  * @fast_training: AUX CH handshake not required for link training
+ * @channel_coding: ANSI 8B/10B channel coding capability
  */
 struct drm_dp_link_caps {
 	bool enhanced_framing;
 	bool tps3_supported;
 	bool fast_training;
+	bool channel_coding;
 };
 
 void drm_dp_link_caps_copy(struct drm_dp_link_caps *dest,
-- 
2.22.0

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