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

From: Karol Herbst <kherbst@redhat.com>
To: Maxime Ripard <maxime@cerno.tech>
Cc: Dom Cobley <dom@raspberrypi.com>,
	Tim Gover <tim.gover@raspberrypi.com>,
	David Airlie <airlied@linux.ie>,
	nouveau <nouveau@lists.freedesktop.org>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	Ben Skeggs <bskeggs@redhat.com>,
	Daniel Vetter <daniel.vetter@intel.com>,
	Phil Elwell <phil@raspberrypi.com>
Subject: Re: [Nouveau] [PATCH v2 13/22] drm/nouveau/kms: Remove redundant zpos initialisation
Date: Mon, 21 Feb 2022 17:42:36 +0100	[thread overview]
Message-ID: <CACO55tt8eTkEZp_DSFQ3Lt3+WBX1g3iwrB6-eTT=91bAk1NPEw@mail.gmail.com> (raw)
In-Reply-To: <20220221095918.18763-14-maxime@cerno.tech>

On Mon, Feb 21, 2022 at 11:00 AM Maxime Ripard <maxime@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@lists.freedesktop.org
> Cc: Ben Skeggs <bskeggs@redhat.com>
> Cc: Karol Herbst <kherbst@redhat.com>
> Cc: Lyude Paul <lyude@redhat.com>
> Signed-off-by: Maxime Ripard <maxime@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.

>  }
>
>  static void

> --
> 2.35.1
>