From: Thierry Reding treding@nvidia.com
While probing the DisplayPort link, query the fast training capability. If supported, drivers can use the fast link training sequence instead of the more involved full link training sequence.
Signed-off-by: Thierry Reding treding@nvidia.com --- 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 982dd9febb1c..2d56aeda1b75 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -334,12 +334,14 @@ EXPORT_SYMBOL(drm_dp_dpcd_read_link_status); static void drm_dp_link_caps_reset(struct drm_dp_link_caps *caps) { caps->enhanced_framing = false; + caps->fast_training = false; }
void drm_dp_link_caps_copy(struct drm_dp_link_caps *dest, const struct drm_dp_link_caps *src) { dest->enhanced_framing = src->enhanced_framing; + dest->fast_training = src->fast_training; } EXPORT_SYMBOL(drm_dp_link_caps_copy);
@@ -385,6 +387,7 @@ int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link) link->max_lanes = drm_dp_max_lane_count(values);
link->caps.enhanced_framing = drm_dp_enhanced_frame_cap(values); + link->caps.fast_training = drm_dp_fast_training_cap(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 85ff67958875..680d6719d463 100644 --- a/include/drm/drm_dp_helper.h +++ b/include/drm/drm_dp_helper.h @@ -976,6 +976,13 @@ drm_dp_is_branch(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) return dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_PRESENT; }
+static inline bool +drm_dp_fast_training_cap(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) +{ + return dpcd[DP_DPCD_REV] >= 0x11 && + (dpcd[DP_MAX_DOWNSPREAD] & DP_NO_AUX_HANDSHAKE_LINK_TRAINING); +} + /* * DisplayPort AUX channel */ @@ -1103,9 +1110,11 @@ int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux, /** * struct drm_dp_link_caps - DP link capabilities * @enhanced_framing: enhanced framing capability (mandatory as of DP 1.2) + * @fast_training: AUX CH handshake not required for link training */ struct drm_dp_link_caps { bool enhanced_framing; + bool fast_training; };
void drm_dp_link_caps_copy(struct drm_dp_link_caps *dest,