[Mesa-dev] [PATCH 8/8] panfrost: Add backend targeting the DRM driver

[Kristian Høgsberg]

On Mon, Mar 4, 2019 at 6:29 PM Dave Airlie <airlied at gmail.com> wrote:
>
> On Tue, 5 Mar 2019 at 12:20, Kristian Høgsberg <hoegsberg at gmail.com> wrote:
> >
> > On Mon, Mar 4, 2019 at 6:11 PM Alyssa Rosenzweig <alyssa at rosenzweig.io> wrote:
> > >
> > > > Why aren't we using regular dma-buf fences here? The submit ioctl
> > > > should be able to take a number of in fences to wait on and return an
> > > > out fence if requested.
> > >
> > > Ah-ha, that sounds like the "proper" approach for mainline. Much of this
> > > was (incorrectly) inherited from the Arm driver. Thank you for the
> > > pointer.
> >
> > I'm not sure - I mean, the submit should take in/out fences, but the
> > atom mechanism here sounds more like it's for declaring the
> > dependencies between multiple batches in a renderpass/frame to allow
> > the kernel to shcedule them? The sync fd may be a little to heavy
> > handed for that, and if you want to express that kind of dependency to
> > allow the kernel to reschedule, maybe we need both?
>
> You should more likely be using syncobjects, not fences.
>
> You can convert syncobjs to fences, but fences consume an fd which you
> only really want if inter-device.

Fence fd's are also required for passing through protocol for explicit
synchronization.

>
> Dave.