From 15ae3b28f8ca406b449d36d36021e96b66aedb5d Mon Sep 17 00:00:00 2001 From: Anthony Koo Date: Mon, 25 Mar 2019 14:30:12 -0400 Subject: [PATCH] drm/amd/display: disable link before changing link settings [Why] If link is already enabled at a different rate (for example 5.4 Gbps) then calling VBIOS command table to switch to a new rate (for example 2.7 Gbps) will not take effect. This can lead to link training failure to occur. [How] If the requested link rate is different than the current link rate, the link must be disabled in order to re-enable at the new link rate. In today's logic it is currently only impacting eDP since DP connection types will always disable the link during display detection, when initial link verification occurs. Signed-off-by: Anthony Koo Reviewed-by: Aric Cyr Acked-by: Leo Li Acked-by: Tony Cheng Signed-off-by: Alex Deucher --- drivers/gpu/drm/amd/display/dc/core/dc_link.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link.c b/drivers/gpu/drm/amd/display/dc/core/dc_link.c index c0d1d83ae4c5..3b1e38e110ee 100644 --- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c +++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c @@ -1396,6 +1396,15 @@ static enum dc_status enable_link_dp( /* get link settings for video mode timing */ decide_link_settings(stream, &link_settings); + /* If link settings are different than current and link already enabled + * then need to disable before programming to new rate. + */ + if (link->link_status.link_active && + (link->cur_link_settings.lane_count != link_settings.lane_count || + link->cur_link_settings.link_rate != link_settings.link_rate)) { + dp_disable_link_phy(link, pipe_ctx->stream->signal); + } + pipe_ctx->stream_res.pix_clk_params.requested_sym_clk = link_settings.link_rate * LINK_RATE_REF_FREQ_IN_KHZ; state->clk_mgr->funcs->update_clocks(state->clk_mgr, state, false); -- 2.30.2