Re: [PATCH v5 00/21] Host1x sync point UAPI should not be used for tracking DRM jobs

Dmitry Osipenko
2021-01-27T21:21:07Z

26.01.2021 05:45, Mikko Perttunen пишет:
>> 2. We will probably need a dedicated drm_tegra_submit_cmd for sync point
>> increments.  The job's sync point will be allocated dynamically when job
>> is submitted.  We will need a fag for the sync_incr and wait_syncpt
>> commands, saying "it's a job's sync point increment/wait"
>
> Negative. Like I have explained in previous discussions, with the
> current way the usage of hardware resources is much more deterministic
> and obvious. I disagree on the point that this is much more complicated
> for the userspace. Separating syncpoint and channel allocation is one of
> the primary motivations of this series for me.

Sync points are a limited resource. The most sensible way to work around
it is to keep sync points within kernel as much as possible. This is not
only much simpler for user space, but also allows to utilize DRM API
properly without re-inventing what already exists and it's easier to
maintain hardware in a good state.

If you need to use a dedicated sync point for VMs, then just allocate
that special sync point and use it. But this sync point won't be used
for jobs tracking by kernel driver. Is there any problem with this?

The primary motivation for me is to get a practically usable kernel
driver for userspace.