[ADL][MTL]HDCP not working with MST: The issue is seen during AKE init when writing the DPCD 0x69000.
Currently, the HDCP on MST is incorrectly using Remote DPCD for authentication instead of talking to immediate downstream device. This was changed, when writing to HDCP related DPCDs from immediate device started failing. The failure to write into HDCP DPCDs is seen during AKE init specifically writing the DPCD 0x69000. Each time when attempted to write the DPCD 0x69000, device is responding with AUX_DEFER. Other DPCD reads/writes are working for example reading RXCaps DPCD 0x6921D is working.
The issue is seen after the commit : 0ff0e219d9b8 (HEAD, refs/bisect/bad) drm/i915: Compute clocks earlier https://cgit.freedesktop.org/drm-tip/commit/?id=0ff0e219d9b8db047d3e800553f238136ed53ed7 which was a part of the series https://patchwork.freedesktop.org/series/103491/
With this change reverted, the DPCD writes to 0x69000 are working.
Logs with the revert: 1_with_revert.txt
Logs without the revert: 1_without_revert.txt
Revert Patch :0001-Revert-drm-i915-Compute-clocks-earlier.patch
Platform : ADL P
MST HUB: Dell docker WD19PV
Panel : Acer CB281HK
The issue is seen with all platforms, tried with ADLP, MTL, RPL with different Dongles and Panels.