[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]

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(-)

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2.25.1