[RFC PATCH 0/7] drm/panfrost: Add a new submit ioctl

[Boris Brezillon]

On Thu, 11 Mar 2021 12:16:33 +0000
Steven Price <steven.price at arm.com> wrote:

> Also the current code completely ignores PANFROST_BO_REF_READ. So either 
> that should be defined as 0, or even better we support 3 modes:
> 
>   * Exclusive ('write' access)
>   * Shared ('read' access)
>   * No fence - ensures the BO is mapped, but doesn't add any implicit 
> fences.

I looked at other drivers and they seem to have this
NO_FENCE/NO_IMPLICIT flag at the job/submit level and conditioned on
the presence of a in_sync_fd file. I can see per-BO NO_FENCE being
useful for sub-buffer accesses, assuming we don't want to deal with
other deps explicitly, but we could also force the NO_IMPLICIT behavior
for the whole job and let the user deal with all deps explicitly. TBH,
it's a bit unclear to me how that feature would be used by the vulkan
driver, so I'd rather leave that NO_FENCE use case for later.