]> git.proxmox.com Git - mirror_ubuntu-jammy-kernel.git/commit
drm/amd/display: fix issues with bad AUX reply on some displays
authorAnthony Koo <anthony.koo@amd.com>
Wed, 15 May 2019 20:39:23 +0000 (16:39 -0400)
committerAlex Deucher <alexander.deucher@amd.com>
Fri, 31 May 2019 15:39:32 +0000 (10:39 -0500)
commit8633d96d3ca14b37dffe303281c1dff320b422fb
tree14cf29b080958ed95cfb10e1c9a992dfb3e741d4
parentc5c07cb5435e75b1b7837dc142bebfa3f9c6a524
drm/amd/display: fix issues with bad AUX reply on some displays

[Why]
Some displays take some time to power up AUX CH once they are
put into D3 state via write to DPCD 600h=2.

Interestingly enough, some display may simply NACK, but some might
also ACK with a bunch of 0s, which can cause issues with receiver
cap retrieval. Note that not all DPCD address return 0s, but in
particular it has been observed on some higher DPCD address such
as DPCD 2200h, etc.

[How]
Based on spec, receiver will monitor differential signal while in D3 and
AUX CH is in low power mode. When detected, it may allow up to
1 ms to power up AUX CH and reply.

If we read Sink power state D3, we should add 1 ms delay to satisfy
this spec requirement.

Signed-off-by: Anthony Koo <anthony.koo@amd.com>
Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c