[PATCH v2 0/1][SRU][F/G/Unstable/OEM-5.6] drm/i915/dp_mst - System would hang during the boot up

[Koba Ko]

BugLink: https://bugs.launchpad.net/bugs/1902469

[Impact]
The machine connect with the external monitor on dock(Thunderbolt),
Then system would hang during the boot-up.

[Fix]
The atomic check hooks must look up the encoder to be used with a
connector from the connector's atomic state, and not assume that it's
the connector's current attached encoder. The latter one can change
under the atomic check func, or can be unset yet as in the case of MST
connectors.

[test]
With the patch, The machine connect with the external monitor on dock(Thunderbolt),
Then system boot up successfully.

[Regression Potential]
Low. This patch is also verified by others and is archived in the drmtip.

V2: 
1. cherry-pick from linux-next.
2. Add Groovy and Unstable.

Imre Deak (1):
  drm/i915: Fix encoder lookup during PSR atomic check

 drivers/gpu/drm/i915/display/intel_psr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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2.25.1