drm/msm/dp: Introduce link training per-segment for LTTPRs

DisplayPort requires per-segment link training when LTTPR are switched
to non-transparent mode, starting with LTTPR closest to the source.
Only when each segment is trained individually, source can link train
to sink.

Implement per-segment link traning when LTTPR(s) are detected, to
support external docking stations. On higher level, changes are:

* Pass phy being trained down to all required helpers
* Run CR, EQ link training per phy
* Set voltage swing, pre-emphasis levels per phy

Since at least some LTTPRs (eg. Parade PS8830) do not correctly report
voltage-swing, pre-emphasis level 3 support, always assume level 3 is
supported. This is permitted under DP 2.1(a) section 3.6.7.2 stating
that LTTPR shall set its transmitter levels as close as possible to
those requested by the DPTX, if the DPTX sets the voltage swing or
pre-emphasis to a level that the LTTPR does not support. It shall be
noted that LTTPR’s level choosing is implementation-specific.

This ensures successful link training both when connected directly to
the monitor (single LTTPR onboard most X1E laptops) and via the docking
station (at least two LTTPRs).

Fixes: 72d0af4accd9 ("drm/msm/dp: Add support for LTTPR handling")
Tested-by: Jessica Zhang <[e-mail]> # SA8775P
Tested-by: Johan Hovold <[e-mail]>
Tested-by: Rob Clark <[e-mail]>
Tested-by: Stefan Schmidt <[e-mail]>
Signed-off-by: Aleksandrs Vinarskis <[e-mail]>
Reviewed-by: Abel Vesa <[e-mail]>
Reviewed-by: Abhinav Kumar <[e-mail]>
Reviewed-by: Dmitry Baryshkov <[e-mail]>
Patchwork: https://patchwork.freedesktop.org/patch/652305/
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Dmitry Baryshkov <[e-mail]>

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

···
 	return 0;
 }
 
-static int msm_dp_ctrl_update_vx_px(struct msm_dp_ctrl_private *ctrl)
+static int msm_dp_ctrl_update_phy_vx_px(struct msm_dp_ctrl_private *ctrl,
+					enum drm_dp_phy dp_phy)
 {
 	struct msm_dp_link *link = ctrl->link;
-	int ret = 0, lane, lane_cnt;
+	int lane, lane_cnt, reg;
+	int ret = 0;
 	u8 buf[4];
 	u32 max_level_reached = 0;
 	u32 voltage_swing_level = link->phy_params.v_level;
···
 
 	drm_dbg_dp(ctrl->drm_dev, "sink: p|v=0x%x\n",
 			voltage_swing_level | pre_emphasis_level);
-	ret = drm_dp_dpcd_write(ctrl->aux, DP_TRAINING_LANE0_SET,
-					buf, lane_cnt);
+
+	if (dp_phy == DP_PHY_DPRX)
+		reg = DP_TRAINING_LANE0_SET;
+	else
+		reg = DP_TRAINING_LANE0_SET_PHY_REPEATER(dp_phy);
+
+	ret = drm_dp_dpcd_write(ctrl->aux, reg, buf, lane_cnt);
 	if (ret == lane_cnt)
 		ret = 0;
 
···
 }
 
 static bool msm_dp_ctrl_train_pattern_set(struct msm_dp_ctrl_private *ctrl,
-		u8 pattern)
+		u8 pattern, enum drm_dp_phy dp_phy)
 {
 	u8 buf;
+	int reg;
 	int ret = 0;
 
 	drm_dbg_dp(ctrl->drm_dev, "sink: pattern=%x\n", pattern);
···
 	if (pattern && pattern != DP_TRAINING_PATTERN_4)
 		buf |= DP_LINK_SCRAMBLING_DISABLE;
 
-	ret = drm_dp_dpcd_writeb(ctrl->aux, DP_TRAINING_PATTERN_SET, buf);
+	if (dp_phy == DP_PHY_DPRX)
+		reg = DP_TRAINING_PATTERN_SET;
+	else
+		reg = DP_TRAINING_PATTERN_SET_PHY_REPEATER(dp_phy);
+
+	ret = drm_dp_dpcd_writeb(ctrl->aux, reg, buf);
 	return ret == 1;
 }
 
 static int msm_dp_ctrl_link_train_1(struct msm_dp_ctrl_private *ctrl,
-			int *training_step)
+			int *training_step, enum drm_dp_phy dp_phy)
 {
+	int delay_us;
 	int tries, old_v_level, ret = 0;
 	u8 link_status[DP_LINK_STATUS_SIZE];
 	int const maximum_retries = 4;
+
+	delay_us = drm_dp_read_clock_recovery_delay(ctrl->aux,
+						    ctrl->panel->dpcd, dp_phy, false);
 
 	msm_dp_catalog_ctrl_state_ctrl(ctrl->catalog, 0);
 
···
 	if (ret)
 		return ret;
 	msm_dp_ctrl_train_pattern_set(ctrl, DP_TRAINING_PATTERN_1 |
-		DP_LINK_SCRAMBLING_DISABLE);
+		DP_LINK_SCRAMBLING_DISABLE, dp_phy);
 
-	ret = msm_dp_ctrl_update_vx_px(ctrl);
+	msm_dp_link_reset_phy_params_vx_px(ctrl->link);
+	ret = msm_dp_ctrl_update_phy_vx_px(ctrl, dp_phy);
 	if (ret)
 		return ret;
 
 	tries = 0;
 	old_v_level = ctrl->link->phy_params.v_level;
 	for (tries = 0; tries < maximum_retries; tries++) {
-		drm_dp_link_train_clock_recovery_delay(ctrl->aux, ctrl->panel->dpcd);
+		fsleep(delay_us);
 
-		ret = drm_dp_dpcd_read_link_status(ctrl->aux, link_status);
+		ret = drm_dp_dpcd_read_phy_link_status(ctrl->aux, dp_phy, link_status);
 		if (ret)
 			return ret;
 
···
 		}
 
 		msm_dp_link_adjust_levels(ctrl->link, link_status);
-		ret = msm_dp_ctrl_update_vx_px(ctrl);
+		ret = msm_dp_ctrl_update_phy_vx_px(ctrl, dp_phy);
 		if (ret)
 			return ret;
 	}
···
 	return 0;
 }
 
-static void msm_dp_ctrl_clear_training_pattern(struct msm_dp_ctrl_private *ctrl)
+static void msm_dp_ctrl_clear_training_pattern(struct msm_dp_ctrl_private *ctrl,
+					       enum drm_dp_phy dp_phy)
 {
-	msm_dp_ctrl_train_pattern_set(ctrl, DP_TRAINING_PATTERN_DISABLE);
-	drm_dp_link_train_channel_eq_delay(ctrl->aux, ctrl->panel->dpcd);
+	int delay_us;
+
+	msm_dp_ctrl_train_pattern_set(ctrl, DP_TRAINING_PATTERN_DISABLE, dp_phy);
+
+	delay_us = drm_dp_read_channel_eq_delay(ctrl->aux,
+						ctrl->panel->dpcd, dp_phy, false);
+	fsleep(delay_us);
 }
 
 static int msm_dp_ctrl_link_train_2(struct msm_dp_ctrl_private *ctrl,
-			int *training_step)
+			int *training_step, enum drm_dp_phy dp_phy)
 {
+	int delay_us;
 	int tries = 0, ret = 0;
 	u8 pattern;
 	u32 state_ctrl_bit;
 	int const maximum_retries = 5;
 	u8 link_status[DP_LINK_STATUS_SIZE];
+
+	delay_us = drm_dp_read_channel_eq_delay(ctrl->aux,
+						ctrl->panel->dpcd, dp_phy, false);
 
 	msm_dp_catalog_ctrl_state_ctrl(ctrl->catalog, 0);
 
···
 	if (ret)
 		return ret;
 
-	msm_dp_ctrl_train_pattern_set(ctrl, pattern);
+	msm_dp_ctrl_train_pattern_set(ctrl, pattern, dp_phy);
 
 	for (tries = 0; tries <= maximum_retries; tries++) {
-		drm_dp_link_train_channel_eq_delay(ctrl->aux, ctrl->panel->dpcd);
+		fsleep(delay_us);
 
-		ret = drm_dp_dpcd_read_link_status(ctrl->aux, link_status);
+		ret = drm_dp_dpcd_read_phy_link_status(ctrl->aux, dp_phy, link_status);
 		if (ret)
 			return ret;
 
···
 		}
 
 		msm_dp_link_adjust_levels(ctrl->link, link_status);
-		ret = msm_dp_ctrl_update_vx_px(ctrl);
+		ret = msm_dp_ctrl_update_phy_vx_px(ctrl, dp_phy);
 		if (ret)
 			return ret;
 
···
 	return -ETIMEDOUT;
 }
 
+static int msm_dp_ctrl_link_train_1_2(struct msm_dp_ctrl_private *ctrl,
+				      int *training_step, enum drm_dp_phy dp_phy)
+{
+	int ret;
+
+	ret = msm_dp_ctrl_link_train_1(ctrl, training_step, dp_phy);
+	if (ret) {
+		DRM_ERROR("link training #1 on phy %d failed. ret=%d\n", dp_phy, ret);
+		return ret;
+	}
+	drm_dbg_dp(ctrl->drm_dev, "link training #1 on phy %d successful\n", dp_phy);
+
+	ret = msm_dp_ctrl_link_train_2(ctrl, training_step, dp_phy);
+	if (ret) {
+		DRM_ERROR("link training #2 on phy %d failed. ret=%d\n", dp_phy, ret);
+		return ret;
+	}
+	drm_dbg_dp(ctrl->drm_dev, "link training #2 on phy %d successful\n", dp_phy);
+
+	return 0;
+}
+
 static int msm_dp_ctrl_link_train(struct msm_dp_ctrl_private *ctrl,
 			int *training_step)
 {
+	int i;
 	int ret = 0;
 	const u8 *dpcd = ctrl->panel->dpcd;
 	u8 encoding[] = { 0, DP_SET_ANSI_8B10B };
···
 	link_info.num_lanes = ctrl->link->link_params.num_lanes;
 	link_info.rate = ctrl->link->link_params.rate;
 	link_info.capabilities = DP_LINK_CAP_ENHANCED_FRAMING;
-
-	msm_dp_link_reset_phy_params_vx_px(ctrl->link);
 
 	msm_dp_aux_link_configure(ctrl->aux, &link_info);
 
···
 				&assr, 1);
 	}
 
-	ret = msm_dp_ctrl_link_train_1(ctrl, training_step);
+	for (i = ctrl->link->lttpr_count - 1; i >= 0; i--) {
+		enum drm_dp_phy dp_phy = DP_PHY_LTTPR(i);
+
+		ret = msm_dp_ctrl_link_train_1_2(ctrl, training_step, dp_phy);
+		msm_dp_ctrl_clear_training_pattern(ctrl, dp_phy);
+
+		if (ret)
+			break;
+	}
+
 	if (ret) {
-		DRM_ERROR("link training #1 failed. ret=%d\n", ret);
+		DRM_ERROR("link training of LTTPR(s) failed. ret=%d\n", ret);
 		goto end;
 	}
 
-	/* print success info as this is a result of user initiated action */
-	drm_dbg_dp(ctrl->drm_dev, "link training #1 successful\n");
-
-	ret = msm_dp_ctrl_link_train_2(ctrl, training_step);
+	ret = msm_dp_ctrl_link_train_1_2(ctrl, training_step, DP_PHY_DPRX);
 	if (ret) {
-		DRM_ERROR("link training #2 failed. ret=%d\n", ret);
+		DRM_ERROR("link training on sink failed. ret=%d\n", ret);
 		goto end;
 	}
-
-	/* print success info as this is a result of user initiated action */
-	drm_dbg_dp(ctrl->drm_dev, "link training #2 successful\n");
 
 end:
 	msm_dp_catalog_ctrl_state_ctrl(ctrl->catalog, 0);
···
 	if (ret)
 		goto end;
 
-	msm_dp_ctrl_clear_training_pattern(ctrl);
+	msm_dp_ctrl_clear_training_pattern(ctrl, DP_PHY_DPRX);
 
 	msm_dp_catalog_ctrl_state_ctrl(ctrl->catalog, DP_STATE_CTRL_SEND_VIDEO);
 
···
 		return false;
 	}
 	msm_dp_catalog_ctrl_send_phy_pattern(ctrl->catalog, pattern_requested);
-	msm_dp_ctrl_update_vx_px(ctrl);
+	msm_dp_ctrl_update_phy_vx_px(ctrl, DP_PHY_DPRX);
 	msm_dp_link_send_test_response(ctrl->link);
 
 	pattern_sent = msm_dp_catalog_ctrl_read_phy_pattern(ctrl->catalog);
···
 			}
 
 			/* stop link training before start re training  */
-			msm_dp_ctrl_clear_training_pattern(ctrl);
+			msm_dp_ctrl_clear_training_pattern(ctrl, DP_PHY_DPRX);
 		}
 
 		rc = msm_dp_ctrl_reinitialize_mainlink(ctrl);
···
 		 * link training failed
 		 * end txing train pattern here
 		 */
-		msm_dp_ctrl_clear_training_pattern(ctrl);
+		msm_dp_ctrl_clear_training_pattern(ctrl, DP_PHY_DPRX);
 
 		msm_dp_ctrl_deinitialize_mainlink(ctrl);
 		rc = -ECONNRESET;
···
 		msm_dp_ctrl_link_retrain(ctrl);
 
 	/* stop txing train pattern to end link training */
-	msm_dp_ctrl_clear_training_pattern(ctrl);
+	msm_dp_ctrl_clear_training_pattern(ctrl, DP_PHY_DPRX);
 
 	/*
 	 * Set up transfer unit values and set controller state to send