Am 21.05.21 um 14:22 schrieb Daniel Stone:
Hi,
On Fri, 21 May 2021 at 10:10, Daniel Vetter <daniel.vetter@xxxxxxxx> wrote:
Currently this has no practial relevance I think because there's not
many who can pull off a setup with panfrost and another gpu in the
same system. But the rules are that if you're setting an exclusive
fence, indicating a gpu write access in the implicit fencing system,
then you need to wait for all fences, not just the previous exclusive
fence.
panfrost against itself has no problem, because it always sets the
exclusive fence (but that's probably something that will need to be
fixed for vulkan and/or multi-engine gpus, or you'll suffer badly).
Also no problem with that against display.
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 :)
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.
Cheers,
Christian.
Cheers,
Daniel
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