Re: [PATCH v5 00/21] Host1x/TegraDRM UAPI

Dmitry Osipenko
2021-01-27T21:29:30Z

26.01.2021 05:45, Mikko Perttunen пишет:
>> 5. The hardware state of sync points should be reset when sync point is
>> requested, not when host1x driver is initialized.
>
> This may be doable, but I don't think it is critical for this UAPI, so
> let's consider it after this series.
>
> The userspace should anyway not be able to assume the initial value of
> the syncpoint upon allocation. The kernel should set it to some high
> value to catch any issues related to wraparound.

This is critical because min != max when sync point is requested.

> Also, this makes code more complicated since it now needs to ensure all
> waits on the syncpoint have completed before freeing the syncpoint,
> which can be nontrivial e.g. if the waiter is in a different virtual
> machine or some other device connected via PCIe (a real usecase).

It sounds to me that these VM sync points should be treated very
separately from a generic sync points, don't you think so? Let's not mix
them and get the generic sync points usable first.