[Nouveau] [PATCH v2 13/22] drm/nouveau/kms: Remove redundant zpos initialisation

[Karol Herbst]

On Tue, Feb 22, 2022 at 3:02 PM Maxime Ripard <maxime at cerno.tech> wrote:
>
> Hi,
>
> On Mon, Feb 21, 2022 at 05:42:36PM +0100, Karol Herbst wrote:
> > On Mon, Feb 21, 2022 at 11:00 AM Maxime Ripard <maxime at cerno.tech> wrote:
> > >
> > > The nouveau KMS driver will call drm_plane_create_zpos_property() with
> > > an init value depending on the plane purpose.
> > >
> > > Since the initial value wasn't carried over in the state, the driver had
> > > to set it again in nv50_wndw_reset(). However, the helpers have been
> > > adjusted to set it properly at reset, so this is not needed anymore.
> > >
> > > Cc: nouveau at lists.freedesktop.org
> > > Cc: Ben Skeggs <bskeggs at redhat.com>
> > > Cc: Karol Herbst <kherbst at redhat.com>
> > > Cc: Lyude Paul <lyude at redhat.com>
> > > Signed-off-by: Maxime Ripard <maxime at cerno.tech>
> > > ---
> > >  drivers/gpu/drm/nouveau/dispnv50/wndw.c | 2 --
> > >  1 file changed, 2 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/nouveau/dispnv50/wndw.c b/drivers/gpu/drm/nouveau/dispnv50/wndw.c
> > > index 133c8736426a..0c1a2ea0ed04 100644
> > > --- a/drivers/gpu/drm/nouveau/dispnv50/wndw.c
> > > +++ b/drivers/gpu/drm/nouveau/dispnv50/wndw.c
> > > @@ -635,8 +635,6 @@ nv50_wndw_reset(struct drm_plane *plane)
> > >                 plane->funcs->atomic_destroy_state(plane, plane->state);
> > >
> > >         __drm_atomic_helper_plane_reset(plane, &asyw->state);
> > > -       plane->state->zpos = nv50_wndw_zpos_default(plane);
> > > -       plane->state->normalized_zpos = nv50_wndw_zpos_default(plane);
> >
> > so reading the surrounding code a little it feels like those
> > assignments actually do something. If my understanding is correct
> > plane->state points to &asyw->state, but asyw was just kzalloced in
> > this function. __drm_atomic_helper_plane_reset doesn't set the zpos or
> > normalized_zpos fields as long as zpos_property is 0, so those fields
> > won't be set with that change anymore.
> >
> > I just don't know if it's fine like that or if this function should
> > set zpos_property instead or something. Anyway, the commit description
> > makes it sound like that an unneeded assignment would be removed here,
> > which doesn't seem to be the case. But I don't really know much about
> > all the drm API interactions, so it might just be fine, mostly asking
> > to get a better idea on how all those pieces fit together.
>
> If you're looking at the code without that patch series, you're right.
>
> These patches change that however:
> https://lore.kernel.org/dri-devel/20220221095918.18763-7-maxime@cerno.tech/
> https://lore.kernel.org/dri-devel/20220221095918.18763-8-maxime@cerno.tech/
>
> So, once they have been applied those assignments are made in
> __drm_atomic_helper_plane_reset and are no longer relevant here.
>

yeah, I saw those, but I see now where I got confused: the arguments
of __drm_atomic_helper_plane_reset and
__drm_atomic_helper_plane_state_reset are swapped, so I thought
&asyw->state being all 0 was the second arg to
__drm_atomic_helper_plane_state_reset. Yeah the code is alright then.

Reviewed-by: Karol Herbst <kherbst at redhat.com>

> Maxime