[PATCH 0/3][SRU][OEM-5.6] Get the extended DPCD according to the related field in the DPCD registers

[Koba Ko]

BugLink: https://bugs.launchpad.net/bugs/1893752

[Impact]
Connect the 4K at 60Hz monitor on WD19, the monitor can't light.

[Fix]
As per DP spec, at first check DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT.               
If DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT is 1, read the DP_DP13_DPCD_REV to 
get the faster capability. 
If DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT is 0, read DP_DPCD_REV. 

[Test]
With the patches, connect 4K at 60Hz monitor on WD19, 
the machine can output the video to the monitor and the monitor can light.

[Regression]
low, Just get one more DPCD from the extended register, 
compare them and get the faster one.

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

Lyude Paul (1):
  drm/i915/dp: Extract drm_dp_read_dpcd_caps()

Oleg Vasilev (1):
  drm: move DP_MAX_DOWNSTREAM_PORTS from i915 to drm core

 drivers/gpu/drm/drm_dp_helper.c               | 187 ++++++++++++++++++
 drivers/gpu/drm/drm_dp_mst_topology.c         |   6 +-
 .../drm/i915/display/intel_display_types.h    |   2 -
 drivers/gpu/drm/i915/display/intel_dp.c       |  56 +-----
 drivers/gpu/drm/i915/display/intel_dp.h       |   1 -
 drivers/gpu/drm/i915/display/intel_lspcon.c   |   2 +-
 include/drm/drm_dp_helper.h                   |   5 +
 7 files changed, 200 insertions(+), 59 deletions(-)

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2.25.1