[PATCH 0/2][F/G/U/OEM-5.10] UBUNTU: SAUCE: Fix the video can't output through WD19TB connected on TGL's Type-C port during cold-boot

[Koba Ko]

BugLink: https://bugs.launchpad.net/bugs/1913372

[Impact]
WD19TB would report the number of lane(2-lane) and it works well on Type-C port 
of TGL platform. Change the LTTPR mode to non-transparent mode, WD19TB would 
report the larger number of lane(4-lane). It's over the type-c port's bandwidth.

[Fix]
The patch is provided by Imre(https://patchwork.freedesktop.org/series/86267/).
Calculate the PBN divider value based on the rate and lane count link parameters 
that the driver uses for all other computation.

[Test Case]
1. Connected the WD19TB with the TGL platform's Type-C port and
connected the external monitor on WD19TB with HDMI/Displayport.
2. Cold boot the TGL platform.
3. Check the monitor can be blinked and the video can output to the monitor.

[Where problems could occur]
It's correct to calculate the PBN divider based on the source's rate 
and lane count, not the mst's capability.

Imre Deak (2):
  drm/dp/mst: Export drm_dp_get_vc_payload_bw()
  drm/i915: Fix the MST PBN divider calculation

 drivers/gpu/drm/drm_dp_mst_topology.c       | 24 +++++++++++++++------
 drivers/gpu/drm/i915/display/intel_dp_mst.c |  4 +++-
 include/drm/drm_dp_mst_helper.h             |  1 +
 3 files changed, 22 insertions(+), 7 deletions(-)

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2.25.1