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

[Ilia Mirkin]

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.

Cheers,

  -ilia