On Thu, Jan 7, 2021 at 12:53 AM Veera Sundaram Sankaran <veeras@xxxxxxxxxxxxxx> wrote: > > Some drivers have hardware capability to get the precise timestamp of > certain events based on which the fences are triggered. This allows it to > set accurate timestamp factoring out any software and IRQ latencies. Add > a timestamp variant of fence signal function, dma_fence_signal_timestamp > to allow drivers to update the precise timestamp for fences. > So, on quick review, this seems mostly sane. Though, it might be good to add some more detail about how the hardware timestamping fits into the kernel's CLOCK_MONOTONIC time domain. I just want to make sure this interface isn't abused to jam raw hardware-domain timestamps into the fence->timestamp, causing the meaning or time-domain of the fence->timestamp to be unclear or inconsistent. It may be useful to add an additional patch to the documentation around the dma_fence structure to make the timestamp field semantics more explicit and avoid confusion? thanks -john
