Hi Emma,
On 12/06/26 14:44, Emma Anholt wrote:
On 2026-06-10 23:17, Iago Toral wrote:
Hi Maíra,
I have a couple of thoughts here:
1. The original code seems to very specifica about targeting this only
for the last job, which makes it look like a very intentional decision,
so I wonder if there is something we are missing here. I am adding Emma
to the CC in case she has any thoughts about it.
2. I am not aware of any issues despite not having implicit sync for
all the jobs in the chanin. Like you mention, this is because user-
space is already trying to handle job depedencies, so I wonder if we
should instead work on the opposite direction and try to drop implicit
sync in the kernel entirely. Would that make sense? What are other
drivers doing in this regard?
Yeah, you should be working toward dropping implicit sync entirely.
tu's VM_BIND is really nice and where you want to be eventually, but
even if not, then you at least want something like
MSM_SUBMIT_NO_IMPLICIT.
I believe the main issue we would have to implement something like
VM_BIND is the fact that V3D only has one global page table (that we
could switch on runtime, but it would come with the cost that all the HW
queues would only be able to operate on BOs from one client).
NO_IMPLICIT would be a more reasonable option.
I probably just didn't think about this implicit sync case in the
initial implementation, because a bin job dependency on results from
another context is just not a thing that's going to happen in practice.
The implicit sync was mostly about render targets / texturing to be
ordered correctly with X11, and about lifetime management of the BO
(which only needed the last use).
But does it make sense to attach the implicit dependencies to the
CACHE_CLEAN job (last job) and not to the RENDER job or the CSD job?
Best regards,
- Maíra
