[PATCH v4 04/13] drm: zynqmp_dp: Adjust training values per-lane

Sean Anderson
2024-04-23T17:19:20Z

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>
---

(no changes since v1)

drivers/gpu/drm/xlnx/zynqmp_dp.c | 23 ++++++++---------------
1 file changed, 8 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c
index fdea1a9710de..79afe4358d06 100644
--- a/drivers/gpu/drm/xlnx/zynqmp_dp.c
+++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c
@@ -605,28 +605,21 @@ 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 (preemphasis >= DP_TRAIN_PRE_EMPH_LEVEL_2)
+ preemphasis |= DP_TRAIN_MAX_PRE_EMPHASIS_REACHED;

- 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;
-
- for (i = 0; i < dp->mode.lane_cnt; i++)
train_set[i] = voltage | preemphasis;
+ }
}

/**
--
2.35.1.1320.gc452695387.dirty