From: Leo (Hanghong) Ma Date: Thu, 7 Nov 2019 21:30:04 +0000 (-0500) Subject: drm/amd/display: Change the delay time before enabling FEC X-Git-Url: http://git.osdn.net/view?a=commitdiff_plain;h=fa11d3c9425354c4b47e40f34d29c5b0949fe4ce;p=uclinux-h8%2Flinux.git 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 Reviewed-by: Harry Wentland Reviewed-by: Nikola Cornij Acked-by: Leo Li Signed-off-by: Alex Deucher --- 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 537b4dee8f22..b10019106030 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 @@ -3951,7 +3951,14 @@ 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) {