drm: zynqmp_dp: Adjust training values per-lane

The feedback we get from the DPRX is per-lane. Make changes using this
information, instead of picking the maximum values from all lanes. This
results in more-consistent training on marginal links.

Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240423171859.3953024-5-sean.anderson@linux.dev

drivers/gpu/drm/xlnx/zynqmp_dp.c

@@ -606,28 +606,21 @@ static void zynqmp_dp_adjust_train(struct zynqmp_dp *dp,
 				   u8 link_status[DP_LINK_STATUS_SIZE])
 {
 	u8 *train_set = dp->train_set;
-	u8 voltage = 0, preemphasis = 0;
 	u8 i;
 
 	for (i = 0; i < dp->mode.lane_cnt; i++) {
-		u8 v = drm_dp_get_adjust_request_voltage(link_status, i);
-		u8 p = drm_dp_get_adjust_request_pre_emphasis(link_status, i);
+		u8 voltage = drm_dp_get_adjust_request_voltage(link_status, i);
+		u8 preemphasis =
+			drm_dp_get_adjust_request_pre_emphasis(link_status, i);
 
-		if (v > voltage)
-			voltage = v;
+		if (voltage >= DP_TRAIN_VOLTAGE_SWING_LEVEL_3)
+			voltage |= DP_TRAIN_MAX_SWING_REACHED;
 
-		if (p > preemphasis)
-			preemphasis = p;
-	}
-
-	if (voltage >= DP_TRAIN_VOLTAGE_SWING_LEVEL_3)
-		voltage |= DP_TRAIN_MAX_SWING_REACHED;
+		if (preemphasis >= DP_TRAIN_PRE_EMPH_LEVEL_2)
+			preemphasis |= DP_TRAIN_MAX_PRE_EMPHASIS_REACHED;
 
-	if (preemphasis >= DP_TRAIN_PRE_EMPH_LEVEL_2)
-		preemphasis |= DP_TRAIN_MAX_PRE_EMPHASIS_REACHED;
-
-	for (i = 0; i < dp->mode.lane_cnt; i++)
 		train_set[i] = voltage | preemphasis;
+	}
 }
 
 /**