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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>
This commit is contained in:
Leo (Hanghong) Ma 2019-11-07 16:30:04 -05:00 committed by Alex Deucher
parent 10bce710fa
commit 28fa24ad14
1 changed files with 8 additions and 1 deletions
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9
drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
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@ -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) {