From: Thierry Reding <tred...@nvidia.com>
Make use of the newly added drm_dp_aux_rd_interval() helper in existing
DP link training helpers and add comments about minimum required delays
mandated by the DP specification.
Signed-off-by: Thierry Reding <tred...@nvidia.com>
---
drivers/gpu/drm/drm_dp_helper.c | 20 ++++++++++++--------
1 file changed, 12 insertions(+), 8 deletions(-)
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 0d9e66ea9667..dabac772dfc3 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -120,11 +120,13 @@ EXPORT_SYMBOL(drm_dp_get_adjust_request_pre_emphasis);
void drm_dp_link_train_clock_recovery_delay(const u8
dpcd[DP_RECEIVER_CAP_SIZE])
{
- unsigned int min;
+ unsigned int min = drm_dp_aux_rd_interval(dpcd);
- if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] != 0)
- min = dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4000;
- else
+ /*
+ * The DP specification mandates a delay of 100 us during clock
+ * recovery if the sink doesn't report an AUX read interval.
+ */
+ if (min == 0)
min = 100;
usleep_range(min, min * 2);
@@ -133,11 +135,13 @@ EXPORT_SYMBOL(drm_dp_link_train_clock_recovery_delay);
void drm_dp_link_train_channel_eq_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
{
- unsigned int min;
+ unsigned int min = drm_dp_aux_rd_interval(dpcd);
- if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] != 0)
- min = dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4000;
- else
+ /*
+ * The DP specification mandates a delay of 400 us during clock
+ * recovery if the sink doesn't report an AUX read interval.
+ */
+ if (min == 0)
min = 400;
usleep_range(min, min * 2);
--
2.15.1
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