[PATCH 0/2 V2][SRU][U/J/OEM-5.14/OEM-5.17] UBUNTU: SAUCE: Fix WD22TB4 suspend and resume, two external monitor can not output

[Tim Gardner]

On 6/20/22 23:33, Koba Ko 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
> 
> V2: Add "UBUNTU: SAUCE:"
> 
> 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(-)
> 

For Jammy/linux I think we ought to wait until these patches are at 
least merged to linux-next.

rtg

-- 
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Tim Gardner
Canonical, Inc