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Date:   Tue, 04 Jul 2023 17:57:06 +0000
To:     Sebastian Wick <sebastian.wick@redhat.com>
From:   Simon Ser <contact@emersion.fr>
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Subject: Re: [PATCH v4 1/6] drm: allow DRM_MODE_PAGE_FLIP_ASYNC for atomic commits
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On Tuesday, July 4th, 2023 at 19:06, Sebastian Wick <sebastian.wick@redhat.=
com> wrote:

> > + * When used with atomic uAPI, the driver will return an error if the =
hardware
> > + * doesn't support performing an asynchronous page-flip for this updat=
e.
> > + * User-space should handle this, e.g. by falling back to a regular pa=
ge-flip.
> > + *
> > + * Note, some hardware might need to perform one last synchronous page=
-flip
> > + * before being able to switch to asynchronous page-flips. As an excep=
tion,
> > + * the driver will return success even though that first page-flip is =
not
> > + * asynchronous.
>=20
> What would happen if one commits another async KMS update before the
> first page flip? Does one receive EAGAIN, does it amend the previous
> commit? What happens to the timing feedback?
>=20
> This seems really risky to include tbh. I would prefer if we would not
> add such special cases for now.

This is not a new case, i915 already does this with the legacy API to
address some hw issues. Sadly I don't think we can do anything about
it.