Fixes to get HDCP2.2 over MST working on MST docking stations with certain behaviors that cause the current flow to fail. Tested with Dell WD-19 and Lenovo ThinkPad USB Type-C Dock Gen 2.
These fixes should make the flow more robust to handle behaviors that as far as I can tell are unclear in the HDCP spec:
RxInfo contains repeater topology information needed for MST. The behavior on these docks is that this can only be read during RepeaterAuth_Send_ReceiverID_List when the RxStatus READY bit is set otherwise the dock will return NACK. It seems these docks treat reading this range at any other time as invalid when the READY bit isn't set possibly because it could be stale. The HDCP spec also states the READY bit is cleared after RxInfo is read.
These fixes address this behavior by only reading RxInfo once during the AKE flow and reusing that data.
Juston Li (3): drm/i915/hdcp: update cp_irq_count_cached in intel_dp_hdcp2_read_msg() drm/i915/hdcp: read RxInfo once when reading RepeaterAuth_Send_ReceiverID_List drm/i915/hdcp: reuse rx_info for mst stream type1 capability check
.../drm/i915/display/intel_display_types.h | 2 + drivers/gpu/drm/i915/display/intel_dp_hdcp.c | 77 +++++-------------- drivers/gpu/drm/i915/display/intel_hdcp.c | 47 +++++------ include/drm/drm_dp_helper.h | 2 +- 4 files changed, 43 insertions(+), 85 deletions(-)