Re: [Freedreno] [PATCH v2 16/22] drm/msm/dpu: do not limit the zpos property

[Dmitry Baryshkov <dmitry.baryshkov@linaro.org>]

On Tue, 9 Nov 2021 at 23:15, <abhinavk@codeaurora.org> wrote:
>
> On 2021-07-04 18:21, Dmitry Baryshkov wrote:
> > Stop limiting zpos property values, we use normalized_zpos anyway. And
> > nothing stops userspace from assigning several planes to a single zpos
> > (it is a userspace bug, but the kernel is forgiving about it).
>
> Userspace assigning several planes to a single zpos was intended to
> identify
> cases where src split can be used. Downstream does not use normalized
> zpos,
> hence it did not come across as a bug but mostly as a way to identify
> when
> usermode needs src split to be enabled based on the composition
> strategy.
>
> We can talk about that more in the rest of the patches of this series.
>
> For this one, I only have a couple of questions:
>
> 1) Across different vendors, some have gone with limiting the zpos and
> some have gone with
> the max, so is there an issue with sticking with the max_blend_stages
> limit?
>
> 2) If there is no hard reason to make this change, I think its better to
> keep it the way it is.

Short answer to both questions: we want to have more planes than the
max_blend_stages. So we should remove the limit.

Consider this to be a unification with MDP5, which uses 255 here.

>
> >
> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> > ---
> >  drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c | 11 +----------
> >  1 file changed, 1 insertion(+), 10 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
> > b/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
> > index 8ed7b8f0db69..3850f2714bf3 100644
> > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
> > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
> > @@ -44,7 +44,6 @@
> >  #define DPU_NAME_SIZE  12
> >
> >  #define DPU_PLANE_COLOR_FILL_FLAG    BIT(31)
> > -#define DPU_ZPOS_MAX 255
> >
> >  /* multirect rect index */
> >  enum {
> > @@ -1374,7 +1373,6 @@ struct drm_plane *dpu_plane_init(struct
> > drm_device *dev,
> >       struct dpu_plane *pdpu;
> >       struct msm_drm_private *priv = dev->dev_private;
> >       struct dpu_kms *kms = to_dpu_kms(priv->kms);
> > -     int zpos_max = DPU_ZPOS_MAX;
> >       uint32_t num_formats;
> >       int ret = -EINVAL;
> >
> > @@ -1412,14 +1410,7 @@ struct drm_plane *dpu_plane_init(struct
> > drm_device *dev,
> >
> >       pdpu->catalog = kms->catalog;
> >
> > -     if (kms->catalog->mixer_count &&
> > -             kms->catalog->mixer[0].sblk->maxblendstages) {
> > -             zpos_max = kms->catalog->mixer[0].sblk->maxblendstages - 1;
> > -             if (zpos_max > DPU_STAGE_MAX - DPU_STAGE_0 - 1)
> > -                     zpos_max = DPU_STAGE_MAX - DPU_STAGE_0 - 1;
> > -     }
> > -
> > -     ret = drm_plane_create_zpos_property(plane, 0, 0, zpos_max);
> > +     ret = drm_plane_create_zpos_property(plane, 0, 0, 255);
> >       if (ret)
> >               DPU_ERROR("failed to install zpos property, rc = %d\n", ret);



-- 
With best wishes
Dmitry