NACK: [PATCH 0/2][SRU][U/J/OEM-5.14/OEM-5.17] Fix WD22TB4 suspend and resume, two external monitor can not output

[Koba Ko]

missed the tag "UBUNTU: SAUCE"


On Tue, Jun 21, 2022 at 1:28 PM Koba Ko <koba.ko at canonical.com> wrote:
>
> BugLink: https://bugs.launchpad.net/bugs/1979267
>
> [Impact]
> Resume SUT from suspend mode, found external monitors can not output, but display setting can recognize external monitors.
>
> [Fix]
> The WD22TB4 Thunderbolt dock at least will revert its DP_MAX_LINK_RATE
> from HBR3 to HBR2 after system suspend/resume if the DP_DP13_DPCD_REV
> registers are not read subsequently also as required.
>
> Fix this by reading DP_DP13_DPCD_REV registers as well, matching what is
> done during connector detection. While at it also fix up the same call
> in drm_dp_mst_dump_topology().
>
> [Test Case]
> 1. Connect two 4K external monitor to WD22TB4.
> 2. Put SUT into suspend mode and wait 30sec
> 3. Resume SUT from suspend mode, found external monitors can not output.
>
> [Where problems could occur]
> low
>
> Imre Deak (1):
>   drm/dp/mst: Read the extended DPCD capabilities during system resume
>
>  drivers/gpu/drm/drm_dp_mst_topology.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
>
> --
> 2.25.1
>