[PATCH 0/1][SRU][F/OEM-5.6] drm/i915/dp_mst - only read the base capability in DPCD.

[Koba Ko]

BugLink: https://bugs.launchpad.net/bugs/1902613

[Impact]
Currently DRM driver assume the source device caps is higher than the MST device
caps. With this commit, the statement would be broken.

e.g. the source device only support DP1.2 and the mst device support DP1.4.

The source device can't output the video to the external monitor on the docking station.

[Fix]
Revert the previous patch and only read the base capability from DPCD.

[test]
With the patch, The machine(DP1.2) connect with the external monitor on docking station(SC) and
can output the video to the external monitor on docking station(SC-DP1.4).

[Regression Potential]
Can't output 4k at 60hz on the docking station(SC).

Koba Ko (1):
  Revert "UBUNTU: SAUCE: drm/dp_mst: Retrieve extended DPCD caps for
    topology manager"

 drivers/gpu/drm/drm_dp_mst_topology.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

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2.17.1