Re: [PATCH 04/11] drm/msm/dpu: allow using lm mixer base stage

[Dmitry Baryshkov]

On 20/04/2023 10:26, Arnaud Vrac wrote:
> Le jeu. 20 avr. 2023 à 00:43, Dmitry Baryshkov
> <dmitry.baryshkov@xxxxxxxxxx> a écrit :
> > On 19/04/2023 17:41, Arnaud Vrac wrote:
> > > The dpu backend already handles applying alpha to the base stage, so we
> > > can use it to render the bottom plane in all cases. This allows mixing
> > > one additional plane with the hardware mixer.
> > >
> > > Signed-off-by: Arnaud Vrac <avrac@xxxxxxxxxx>
> >
> > This might require additional changes. First, for the STAGE_BASE pipe
> > in the source split mode (iow using two LMs) should programmed with
> > respect to the right LM's x offset (rather than usual left top-left LM).
> > See  mdss_mdp_pipe_position_update().
>
> Ok, I did test with 2 LMs and it seems to be working, I'll investigate.

The only reference I have here is the fbdev driver, see [1]. The newer 
SDE driver doesn't handle STAGE_BASE vs STAGE0 (and DPU inherited that 
design). Maybe this got fixed in hw at some point.

[1] 
https://git.codelinaro.org/clo/la/kernel/msm-4.19/-/blob/LE.UM.4.4.1.r2-17500-QRB5165.0/drivers/video/fbdev/msm/mdss_mdp_pipe.c#L1789

I think, it only concerns the src_split + multirect cases, where the 
rectangle base point is on the right LM.

> > Also this might need some interaction with CTL_MIXER_BORDER_OUT being
> > set or not. If I remember correctly, if there bottom plane is not
> > fullscreen or if there are no planes at all, we should set
> > CTL_MIXER_BORDER_OUT (which takes STAGE_BASE) and start assigning them
> > from STAGE0. If not, we can use STAGE_BASE.
>
> I also tested with both fullscreen and non-fullscreen primary plane,
> and no plane. I'll check this.

Yes, the DPU driver always enables the MIXER_BORDER_OUT.

> > > ---
> > >    drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c | 2 +-
> > >    1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
> > > index 14b5cfe306113..148921ed62f85 100644
> > > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
> > > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
> > > @@ -881,7 +881,7 @@ static int dpu_plane_atomic_check(struct drm_plane *plane,
> > >        r_pipe->multirect_mode = DPU_SSPP_MULTIRECT_NONE;
> > >        r_pipe->sspp = NULL;
> > >
> > > -     pstate->stage = DPU_STAGE_0 + pstate->base.normalized_zpos;
> > > +     pstate->stage = DPU_STAGE_BASE + pstate->base.normalized_zpos;
> > >        if (pstate->stage >= pdpu->catalog->caps->max_mixer_blendstages) {
> > >                DPU_ERROR("> %d plane stages assigned\n",
> > >                          pdpu->catalog->caps->max_mixer_blendstages - DPU_STAGE_0);
> >
> > --
> > With best wishes
> > Dmitry

--
With best wishes
Dmitry