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authorLeo (Hanghong) Ma <hanghong.ma@amd.com>2019-11-07 16:30:04 -0500
committerAlex Deucher <alexander.deucher@amd.com>2019-12-05 18:18:33 -0500
commit28fa24ad14e8f7d23c62283eaf9c79b4fd165c16 (patch)
tree34a59e358f75fdd46cc8364470eadb5215dfa532 /drivers/gpu
parent10bce710fa6feb13ec270d5420aad3b81f6bf7ea (diff)
downloadlinux-28fa24ad14e8f7d23c62283eaf9c79b4fd165c16.tar.bz2
drm/amd/display: Change the delay time before enabling FEC
[why] DP spec requires 1000 symbols delay between the end of link training and enabling FEC in the stream. Currently we are using 1 miliseconds delay which is not accurate. [how] One lane RBR should have the maximum time for transmitting 1000 LL codes which is 6.173 us. So using 7 microseconds delay instead of 1 miliseconds. Signed-off-by: Leo (Hanghong) Ma <hanghong.ma@amd.com> Reviewed-by: Harry Wentland <Harry.Wentland@amd.com> Reviewed-by: Nikola Cornij <Nikola.Cornij@amd.com> Acked-by: Leo Li <sunpeng.li@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Diffstat (limited to 'drivers/gpu')
-rw-r--r--drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
index 0f59b68aa4c2..504055fc70e8 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
@@ -3522,7 +3522,14 @@ void dp_set_fec_enable(struct dc_link *link, bool enable)
if (link_enc->funcs->fec_set_enable &&
link->dpcd_caps.fec_cap.bits.FEC_CAPABLE) {
if (link->fec_state == dc_link_fec_ready && enable) {
- msleep(1);
+ /* Accord to DP spec, FEC enable sequence can first
+ * be transmitted anytime after 1000 LL codes have
+ * been transmitted on the link after link training
+ * completion. Using 1 lane RBR should have the maximum
+ * time for transmitting 1000 LL codes which is 6.173 us.
+ * So use 7 microseconds delay instead.
+ */
+ udelay(7);
link_enc->funcs->fec_set_enable(link_enc, true);
link->fec_state = dc_link_fec_enabled;
} else if (link->fec_state == dc_link_fec_enabled && !enable) {