tree 00862914b9452f134581db4928085c2473e8c875
parent 3ae42acde349e0f983945da5901282de9352d929
author Hugo Hu <hugo.hu@amd.com> 1551093412 +0800
committer Alex Deucher <alexander.deucher@amd.com> 1553744492 -0500

drm/amd/display: Handle branch device with DFP count = 0 case.

[Why]
When you have a SST branch device the driver, Even no sink device connected,
it also send HPD with a valid EDID. Driver will config it to DP sink.
Therefore, there're two displays in display setting.

DPCD 0x05, DFP_PRESENT = 1 (branch device),
DFP_TYPE = 00 (Display Port)

[How]
Driver determine DPCD 0x05 DFP_PRESENT = 1(branch) as an active dongle
And check DFP count.

Signed-off-by: Hugo Hu <hugo.hu@amd.com>
Reviewed-by: Hugo Hu <Hugo.Hu@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>