I have been trying to upstream the TAPRIO (Time Aware Priority Shaper) support for ICSSG driver for a while now. During upstreaming we caught few limitations on firmware side. Maintainers want these limitations to be fixed before going forward with the series. Full details can be found in the thread [ https://lore.kernel.org/all/20240606141759.pzug3gezeuabrxzm@skbuf/|https://lore.kernel.org/all/20240606141759.pzug3gezeuabrxzm@skbuf/]{}

Firmware can’t handle base-time which is not a precise multiple of cycle-time. Currently firmware only implements schedule with base-time being multiple of cycle_time. Let’s say cycle-time is 1ms and base-time is 2000.5 ms. Then the firmware will start scheduling at 2001 ms. If the base-time is 2000.6 then still firmware will start the schedule at 2000.6 ms. Firmware can not differentiate between two base-time whose difference is less then cycle time. To firmware a base-time of 0 ns and a base time of 1000 ns will be treated as same.

1. The ask here is for firmware is to be able to differentiate different base-times and to be able to schedule even if the base-time is not multiple of cycle_time.