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

diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c
index 43f47c8a51a0c53fd36e1192dd90cfa3edb70a1f..9df068a413f376d70443c955e6cb19e28f2683fe 100644 (file)
--- a/drivers/gpu/drm/xlnx/zynqmp_dp.c
+++ b/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;
+       }
 }
 
 /**