drm/msm/dp: reduce link rate if failed at link training 1

Reduce link rate and re start link training if link training 1
failed due to loss of clock recovery done to fix Link Layer
CTS case 4.3.1.7.  Also only update voltage and pre-emphasis
swing level after link training started to fix Link Layer CTS
case 4.3.1.6.

Changes in V2:
-- replaced cr_status with link_status[DP_LINK_STATUS_SIZE]
-- replaced dp_ctrl_any_lane_cr_done() with dp_ctrl_colco_recovery_any_ok()
-- replaced dp_ctrl_any_ane_cr_lose() with !drm_dp_clock_recovery_ok()

Changes in V3:
-- return failed if lane_count <= 1
Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/1628196295-7382-3-git-send-email-khsieh@codeaurora.org
[remove unused cr_status variable]
Signed-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/msm/dp/dp_ctrl.c

@@ -81,13 +81,6 @@ struct dp_ctrl_private {
 	struct completion video_comp;
 };
 
-struct dp_cr_status {
-	u8 lane_0_1;
-	u8 lane_2_3;
-};
-
-#define DP_LANE0_1_CR_DONE	0x11
-
 static int dp_aux_link_configure(struct drm_dp_aux *aux,
 					struct dp_link_info *link)
 {
@@ -1080,7 +1073,7 @@ static int dp_ctrl_read_link_status(struct dp_ctrl_private *ctrl,
 }
 
 static int dp_ctrl_link_train_1(struct dp_ctrl_private *ctrl,
-		struct dp_cr_status *cr, int *training_step)
+			int *training_step)
 {
 	int tries, old_v_level, ret = 0;
 	u8 link_status[DP_LINK_STATUS_SIZE];
@@ -1109,9 +1102,6 @@ static int dp_ctrl_link_train_1(struct dp_ctrl_private *ctrl,
 		if (ret)
 			return ret;
 
-		cr->lane_0_1 = link_status[0];
-		cr->lane_2_3 = link_status[1];
-
 		if (drm_dp_clock_recovery_ok(link_status,
 			ctrl->link->link_params.num_lanes)) {
 			return 0;
@@ -1188,7 +1178,7 @@ static void dp_ctrl_clear_training_pattern(struct dp_ctrl_private *ctrl)
 }
 
 static int dp_ctrl_link_train_2(struct dp_ctrl_private *ctrl,
-		struct dp_cr_status *cr, int *training_step)
+			int *training_step)
 {
 	int tries = 0, ret = 0;
 	char pattern;
@@ -1204,10 +1194,6 @@ static int dp_ctrl_link_train_2(struct dp_ctrl_private *ctrl,
 	else
 		pattern = DP_TRAINING_PATTERN_2;
 
-	ret = dp_ctrl_update_vx_px(ctrl);
-	if (ret)
-		return ret;
-
 	ret = dp_catalog_ctrl_set_pattern(ctrl->catalog, pattern);
 	if (ret)
 		return ret;
@@ -1220,8 +1206,6 @@ static int dp_ctrl_link_train_2(struct dp_ctrl_private *ctrl,
 		ret = dp_ctrl_read_link_status(ctrl, link_status);
 		if (ret)
 			return ret;
-		cr->lane_0_1 = link_status[0];
-		cr->lane_2_3 = link_status[1];
 
 		if (drm_dp_channel_eq_ok(link_status,
 			ctrl->link->link_params.num_lanes)) {
@@ -1241,7 +1225,7 @@ static int dp_ctrl_link_train_2(struct dp_ctrl_private *ctrl,
 static int dp_ctrl_reinitialize_mainlink(struct dp_ctrl_private *ctrl);
 
 static int dp_ctrl_link_train(struct dp_ctrl_private *ctrl,
-		struct dp_cr_status *cr, int *training_step)
+			int *training_step)
 {
 	int ret = 0;
 	u8 encoding = DP_SET_ANSI_8B10B;
@@ -1257,7 +1241,7 @@ static int dp_ctrl_link_train(struct dp_ctrl_private *ctrl,
 	drm_dp_dpcd_write(ctrl->aux, DP_MAIN_LINK_CHANNEL_CODING_SET,
 				&encoding, 1);
 
-	ret = dp_ctrl_link_train_1(ctrl, cr, training_step);
+	ret = dp_ctrl_link_train_1(ctrl, training_step);
 	if (ret) {
 		DRM_ERROR("link training #1 failed. ret=%d\n", ret);
 		goto end;
@@ -1266,7 +1250,7 @@ static int dp_ctrl_link_train(struct dp_ctrl_private *ctrl,
 	/* print success info as this is a result of user initiated action */
 	DRM_DEBUG_DP("link training #1 successful\n");
 
-	ret = dp_ctrl_link_train_2(ctrl, cr, training_step);
+	ret = dp_ctrl_link_train_2(ctrl, training_step);
 	if (ret) {
 		DRM_ERROR("link training #2 failed. ret=%d\n", ret);
 		goto end;
@@ -1282,7 +1266,7 @@ static int dp_ctrl_link_train(struct dp_ctrl_private *ctrl,
 }
 
 static int dp_ctrl_setup_main_link(struct dp_ctrl_private *ctrl,
-		struct dp_cr_status *cr, int *training_step)
+			int *training_step)
 {
 	int ret = 0;
 
@@ -1297,7 +1281,7 @@ static int dp_ctrl_setup_main_link(struct dp_ctrl_private *ctrl,
 	 * a link training pattern, we have to first do soft reset.
 	 */
 
-	ret = dp_ctrl_link_train(ctrl, cr, training_step);
+	ret = dp_ctrl_link_train(ctrl, training_step);
 
 	return ret;
 }
@@ -1495,14 +1479,13 @@ static int dp_ctrl_deinitialize_mainlink(struct dp_ctrl_private *ctrl)
 static int dp_ctrl_link_maintenance(struct dp_ctrl_private *ctrl)
 {
 	int ret = 0;
-	struct dp_cr_status cr;
 	int training_step = DP_TRAINING_NONE;
 
 	dp_ctrl_push_idle(&ctrl->dp_ctrl);
 
 	ctrl->dp_ctrl.pixel_rate = ctrl->panel->dp_mode.drm_mode.clock;
 
-	ret = dp_ctrl_setup_main_link(ctrl, &cr, &training_step);
+	ret = dp_ctrl_setup_main_link(ctrl, &training_step);
 	if (ret)
 		goto end;
 
@@ -1633,6 +1616,25 @@ void dp_ctrl_handle_sink_request(struct dp_ctrl *dp_ctrl)
 	}
 }
 
+static bool dp_ctrl_clock_recovery_any_ok(
+			const u8 link_status[DP_LINK_STATUS_SIZE],
+			int lane_count)
+{
+	int reduced_cnt;
+
+	if (lane_count <= 1)
+		return false;
+
+	/*
+	 * only interested in the lane number after reduced
+	 * lane_count = 4, then only interested in 2 lanes
+	 * lane_count = 2, then only interested in 1 lane
+	 */
+	reduced_cnt = lane_count >> 1;
+
+	return drm_dp_clock_recovery_ok(link_status, reduced_cnt);
+}
+
 int dp_ctrl_on_link(struct dp_ctrl *dp_ctrl)
 {
 	int rc = 0;
@@ -1640,7 +1642,7 @@ int dp_ctrl_on_link(struct dp_ctrl *dp_ctrl)
 	u32 rate = 0;
 	int link_train_max_retries = 5;
 	u32 const phy_cts_pixel_clk_khz = 148500;
-	struct dp_cr_status cr;
+	u8 link_status[DP_LINK_STATUS_SIZE];
 	unsigned int training_step;
 
 	if (!dp_ctrl)
@@ -1680,19 +1682,21 @@ int dp_ctrl_on_link(struct dp_ctrl *dp_ctrl)
 		}
 
 		training_step = DP_TRAINING_NONE;
-		rc = dp_ctrl_setup_main_link(ctrl, &cr, &training_step);
+		rc = dp_ctrl_setup_main_link(ctrl, &training_step);
 		if (rc == 0) {
 			/* training completed successfully */
 			break;
 		} else if (training_step == DP_TRAINING_1) {
 			/* link train_1 failed */
-			if (!dp_catalog_link_is_connected(ctrl->catalog)) {
+			if (!dp_catalog_link_is_connected(ctrl->catalog))
 				break;
-			}
+
+			dp_ctrl_read_link_status(ctrl, link_status);
 
 			rc = dp_ctrl_link_rate_down_shift(ctrl);
 			if (rc < 0) { /* already in RBR = 1.6G */
-				if (cr.lane_0_1 & DP_LANE0_1_CR_DONE) {
+				if (dp_ctrl_clock_recovery_any_ok(link_status,
+					ctrl->link->link_params.num_lanes)) {
 					/*
 					 * some lanes are ready,
 					 * reduce lane number
@@ -1708,12 +1712,18 @@ int dp_ctrl_on_link(struct dp_ctrl *dp_ctrl)
 				}
 			}
 		} else if (training_step == DP_TRAINING_2) {
-			/* link train_2 failed, lower lane rate */
-			if (!dp_catalog_link_is_connected(ctrl->catalog)) {
+			/* link train_2 failed */
+			if (!dp_catalog_link_is_connected(ctrl->catalog))
 				break;
-			}
 
-			rc = dp_ctrl_link_lane_down_shift(ctrl);
+			dp_ctrl_read_link_status(ctrl, link_status);
+
+			if (!drm_dp_clock_recovery_ok(link_status,
+					ctrl->link->link_params.num_lanes))
+				rc = dp_ctrl_link_rate_down_shift(ctrl);
+			else
+				rc = dp_ctrl_link_lane_down_shift(ctrl);
+
 			if (rc < 0) {
 				/* end with failure */
 				break; /* lane == 1 already */