[PATCH v1] drm/bridge: analogix_dp: Apply standard DP training delay helpers

[Damon Ding]

Replace hardcoded fixed usleep_range() delays during clock recovery and
channel equalization with drm_dp_link_train_clock_recovery_delay()
and drm_dp_link_train_channel_eq_delay() helpers.

The original fixed delays are only valid for the case where bit[6:0] of
DPCD TRAINING_AUX_RD_INTERVAL(0000Eh) is 0x00, while core helpers apply
spec-compliant timings matching actual receiver capability values.

Additionally, add dpcd buffer to struct analogix_dp_device to cache
receiver capabilities. Call drm_dp_read_dpcd_caps() at commit entry to
populate cached DPCD data for subsequent link training steps, and
prepare for further usage of other DP helper APIs.

Signed-off-by: Damon Ding <damon.ding@xxxxxxxxxxxxxx>
---
 drivers/gpu/drm/bridge/analogix/analogix_dp_core.c | 10 ++++++++--
 drivers/gpu/drm/bridge/analogix/analogix_dp_core.h |  2 ++
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
index 1d39a354c3d9..30c0c0b41d5a 100644
--- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
+++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
@@ -330,7 +330,7 @@ static int analogix_dp_process_clock_recovery(struct analogix_dp_device *dp)
 	u8 voltage_swing, pre_emphasis, training_lane;
 	u8 link_status[DP_LINK_STATUS_SIZE];
 
-	usleep_range(100, 101);
+	drm_dp_link_train_clock_recovery_delay(&dp->aux, dp->dpcd);
 
 	lane_count = dp->link_train.lane_count;
 
@@ -393,7 +393,7 @@ static int analogix_dp_process_equalizer_training(struct analogix_dp_device *dp)
 	u32 reg;
 	u8 link_status[DP_LINK_STATUS_SIZE];
 
-	usleep_range(400, 401);
+	drm_dp_link_train_channel_eq_delay(&dp->aux, dp->dpcd);
 
 	lane_count = dp->link_train.lane_count;
 
@@ -754,6 +754,12 @@ static int analogix_dp_commit(struct analogix_dp_device *dp)
 {
 	int ret;
 
+	ret = drm_dp_read_dpcd_caps(&dp->aux, dp->dpcd);
+	if (ret < 0) {
+		dev_err(dp->dev, "failed to read dpcd caps: %d\n", ret);
+		return ret;
+	}
+
 	ret = analogix_dp_train_link(dp);
 	if (ret) {
 		dev_err(dp->dev, "unable to do link train, ret=%d\n", ret);
diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.h b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.h
index 94348c4e3623..c7997677a286 100644
--- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.h
+++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.h
@@ -169,6 +169,8 @@ struct analogix_dp_device {
 	bool			fast_train_enable;
 	bool			psr_supported;
 
+	u8 dpcd[DP_RECEIVER_CAP_SIZE];
+
 	struct analogix_dp_plat_data *plat_data;
 };
 
-- 
2.34.1