[PATCH] drm/atomic: Perform blocking commits on workqueue

[Michel Dänzer]

On 9/28/23 14:59, Ray Strode wrote:
> On Thu, Sep 28, 2023 at 5:43 AM Michel Dänzer
> <michel.daenzer at mailbox.org> wrote:
>>>>> When it's really not desirable to account the CPU overhead to the
>>>>> process initiating it then you probably rather want to use an non
>>>>> blocking commit plus a dma_fence to wait for the work to end from userspace.
>>>> Well, first I don't think that's very convenient. You're talking about
>>>> a per-plane property, so there would need to be a separate file
>>>> descriptor allocated for every plane, right? and user-space would have
>>>> to block on all of them before proceeding?
>>
>> OUT_FENCE_PTR is a per-CRTC property, not per-plane.
> 
> Okay, sure.
> 
>> Also, at least in this particular case, a single sync file (not dma_fence) for any CRTC might suffice.
> 
> I don't see how we could rely on that given the provided api and
> multitude of drivers. It might work and then break randomly.

If it's supposed to work from the KMS API PoV, any bugs to the contrary should be fixed.

I'm not really seeing the big difference between using a single fence or multiple, anyway.


I do wonder if there might be a time window where the out fences have signalled, but the atomic commit ioctl will still fail with EBUSY. If there is though, I'd expect it to affect the flip completion events as well.


-- 
Earthling Michel Dänzer            |                  https://redhat.com
Libre software enthusiast          |         Mesa and Xwayland developer