[Linaro-mm-sig] [PATCH 04/11] drm/panfrost: Fix implicit sync

[Daniel Stone]

On Fri, 21 May 2021 at 13:28, Christian König <christian.koenig at amd.com> wrote:
> Am 21.05.21 um 14:22 schrieb Daniel Stone:
> > Yeah, the 'second-generation Valhall' GPUs coming later this year /
> > early next year are starting to get pretty weird. Firmware-mediated
> > job scheduling out of multiple queues, userspace having direct access
> > to the queues and can do inter-queue synchronisation (at least I think
> > so), etc. For bonus points, synchronisation is based on $addr = $val
> > to signal and $addr == $val to wait, with a separate fence primitive
> > as well.
>
> Well that sounds familiar :)

I laughed when I first saw it, because it was better than crying I guess.

If you're curious, the interface definitions are in the csf/ directory
in the 'Bifrost kernel driver' r30p0 download you can get from the Arm
developer site. Unfortunately the exact semantics aren't completely
clear.

> > Obviously Arm should be part of this conversation here, but I guess
> > we'll have to wait for a while yet to see how everything's shaken out
> > with this new gen, and hope that whatever's been designed upstream in
> > the meantime is actually vaguely compatible ...
>
> Yeah, going to keep you in CC when we start to code and review user fences.

Awesome, thanks Christian. Appreciate it. :)

Cheers,
Daniel