From 59b888198843ef6353b293b423c407ba8b625278 Mon Sep 17 00:00:00 2001 From: Peichen Huang Date: Tue, 18 Nov 2025 11:19:36 +0800 Subject: [PATCH] drm/amd/display: Don't disable DPCD mst_en if sink connected [ Upstream commit 9aeb31b2456452257ad1ff7ec566f21bab1f3e8a ] [WHY] User may connect mst dock with multi monitors and do quick unplug and plug in one of the monitor. This operatioin may create CSN from dock to display driver. Then display driver would disable and then enable mst link and also disable/enable DPCD mst_en bit in dock RX. However, when mst_en bit being disabled, if dock has another CSN message to transmit then the message would be removed because of the disabling of mst_en. In this case, the message is missing and it ends up no display in the replugged monitor. [HOW] Don't disable mst_en bit when link still has sink connected. Reviewed-by: Wenjing Liu Signed-off-by: Peichen Huang Signed-off-by: Chenyu Chen Tested-by: Daniel Wheeler Signed-off-by: Alex Deucher Signed-off-by: Sasha Levin --- drivers/gpu/drm/amd/display/dc/link/link_dpms.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/drivers/gpu/drm/amd/display/dc/link/link_dpms.c b/drivers/gpu/drm/amd/display/dc/link/link_dpms.c index b66fbcb0040d..a084c698ed6e 100644 --- a/drivers/gpu/drm/amd/display/dc/link/link_dpms.c +++ b/drivers/gpu/drm/amd/display/dc/link/link_dpms.c @@ -1928,7 +1928,7 @@ static void disable_link_dp(struct dc_link *link, link->dc->hwss.edp_power_control(link, false); } - if (signal == SIGNAL_TYPE_DISPLAY_PORT_MST) + if (signal == SIGNAL_TYPE_DISPLAY_PORT_MST && link->sink_count == 0) /* set the sink to SST mode after disabling the link */ enable_mst_on_sink(link, false); @@ -2079,7 +2079,12 @@ static enum dc_status enable_link_dp(struct dc_state *state, pipe_ctx->stream->signal == SIGNAL_TYPE_DISPLAY_PORT && link->dc->debug.set_mst_en_for_sst) { enable_mst_on_sink(link, true); + } else if (link->dpcd_caps.is_mst_capable && + pipe_ctx->stream->signal == SIGNAL_TYPE_DISPLAY_PORT) { + /* disable mst on sink */ + enable_mst_on_sink(link, false); } + if (pipe_ctx->stream->signal == SIGNAL_TYPE_EDP) { /*in case it is not on*/ if (!link->dc->config.edp_no_power_sequencing) @@ -2358,9 +2363,9 @@ void link_set_dpms_off(struct pipe_ctx *pipe_ctx) if (pipe_ctx->stream->sink) { if (pipe_ctx->stream->sink->sink_signal != SIGNAL_TYPE_VIRTUAL && pipe_ctx->stream->sink->sink_signal != SIGNAL_TYPE_NONE) { - DC_LOG_DC("%s pipe_ctx dispname=%s signal=%x link=%d\n", __func__, + DC_LOG_DC("%s pipe_ctx dispname=%s signal=%x link=%d sink_count=%d\n", __func__, pipe_ctx->stream->sink->edid_caps.display_name, - pipe_ctx->stream->signal, link->link_index); + pipe_ctx->stream->signal, link->link_index, link->sink_count); } } @@ -2474,10 +2479,11 @@ void link_set_dpms_on( if (pipe_ctx->stream->sink) { if (pipe_ctx->stream->sink->sink_signal != SIGNAL_TYPE_VIRTUAL && pipe_ctx->stream->sink->sink_signal != SIGNAL_TYPE_NONE) { - DC_LOG_DC("%s pipe_ctx dispname=%s signal=%x link=%d\n", __func__, + DC_LOG_DC("%s pipe_ctx dispname=%s signal=%x link=%d sink_count=%d\n", __func__, pipe_ctx->stream->sink->edid_caps.display_name, pipe_ctx->stream->signal, - link->link_index); + link->link_index, + link->sink_count); } }