[PATCH] drm/amd/display: Fix pageflipping for XOrg in Linux 5.11+

[Mario Kleiner]

On Sat, Jan 2, 2021 at 7:51 PM Ilia Mirkin <imirkin at alum.mit.edu> wrote:

> On Sat, Jan 2, 2021 at 1:35 PM Mario Kleiner <mario.kleiner.de at gmail.com>
> wrote:
> > I'm less sure about nouveau. It uses modifiers, but has atomic support
> > only on nv50+ and that atomic support is off by default -- needs a
> > nouveau.nouveau_atomic=1 boot parameter to switch it on. It seems to
> > enable modifier support unconditionally regardless if atomic or not,
> > see:
> >
> https://elixir.bootlin.com/linux/v5.11-rc1/source/drivers/gpu/drm/nouveau/nouveau_display.c#L703
> >
> > Atm. nouveau doesn't assign a new format_info though, so wouldn't
> > trigger this issue atm.
>
> Note that pre-nv50, no modifiers exist. Also,
> drm_drv_uses_atomic_modeset() doesn't care whether the client is an
> atomic client or not. It will return true for nv50+ no matter what.
> nouveau_atomic=1 affects whether atomic UAPI is exposed. Not sure if
> this impacts your discussion.
>
>
Thanks Ilia. So nouveau is fine in any case, as nv50 => modifiers and
atomic commit even if atomic UAPI is off. Also
drm_drv_uses_atomic_modeset() is the right choice, as my patch should check
if the atomic driver uses atomic commit, it doesn't care about atomic UAPI
or the client being atomic.

-mario
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