From: Harry Wentland harry.wentland@amd.com
[ Upstream commit 3eb6d7aca53d81ce888624f09cd44dc0302161e8 ]
[WHY] Two years ago the patch referenced by the Fixes tag stopped running dp_verify_link_cap_with_retries during DP detection when the reason for the detection was a short-pulse interrupt. This effectively meant that we were no longer doing the verify_link_cap training on active dongles when their SINK_COUNT changed from 0 to 1.
A year ago this was partly remedied with: commit 80adaebd2d41 ("drm/amd/display: Don't skip link training for empty dongle")
This made sure that we trained the dongle on initial hotplug (without connected downstream devices).
This is all fine and dandy if it weren't for the fact that there are some dongles on the market that don't like link training when SINK_COUNT is 0 These dongles will in fact indicate a SINK_COUNT of 0 immediately after hotplug, even when a downstream device is connected, and then trigger a shortpulse interrupt indicating a SINK_COUNT change to 1.
In order to play nicely we will need our policy to not link train an active DP dongle when SINK_COUNT is 0 but ensure we train it when the SINK_COUNT changes to 1.
[HOW] Call dp_verify_link_cap_with_retries on detection even when the detection is triggered from a short pulse interrupt.
With this change we can also revert this commit which we'll do in a separate follow-up change: commit 80adaebd2d41 ("drm/amd/display: Don't skip link training for empty dongle")
Fixes: 0301ccbaf67d ("drm/amd/display: DP Compliance 400.1.1 failure") Suggested-by: Louis Li Ching-shih.Li@amd.com Tested-by: Louis Li Ching-shih.Li@amd.com Cc: Wenjing Liu Wenjing.Liu@amd.com Cc: Hersen Wu hersenxs.wu@amd.com Cc: Eric Yang Eric.Yang2@amd.com Reviewed-by: Wenjing Liu Wenjing.Liu@amd.com Signed-off-by: Harry Wentland harry.wentland@amd.com Signed-off-by: Alex Deucher alexander.deucher@amd.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/amd/display/dc/core/dc_link.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
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 2f42964fb9f45..3abc0294c05f5 100644 --- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c +++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c @@ -780,8 +780,7 @@ bool dc_link_detect(struct dc_link *link, enum dc_detect_reason reason) same_edid = is_same_edid(&prev_sink->dc_edid, &sink->dc_edid);
if (link->connector_signal == SIGNAL_TYPE_DISPLAY_PORT && - sink_caps.transaction_type == DDC_TRANSACTION_TYPE_I2C_OVER_AUX && - reason != DETECT_REASON_HPDRX) { + sink_caps.transaction_type == DDC_TRANSACTION_TYPE_I2C_OVER_AUX) { /* * TODO debug why Dell 2413 doesn't like * two link trainings