Re: [PATCH v6 12/15] drm/msm/dpu: blend pipes per mixer pairs config

From: Dmitry Baryshkov
Date: Fri Feb 21 2025 - 11:31:35 EST

On Fri, 21 Feb 2025 at 18:12, Jun Nie <jun.nie@xxxxxxxxxx> wrote:
>
> Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx> 于2025年2月21日周五 22:21写道：
> >
> > On Fri, Feb 21, 2025 at 04:07:45PM +0800, Jun Nie wrote:
> > > Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx> 于2025年2月21日周五 00:17写道：
> > > >
> > > > On Thu, Feb 20, 2025 at 11:48:45PM +0800, Jun Nie wrote:
> > > > > Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx> 于2025年2月18日周二 03:57写道：
> > > > > >
> > > > > > On Mon, Feb 17, 2025 at 10:16:01PM +0800, Jun Nie wrote:
> > > > > > > Currently, only 2 pipes are used at most for a plane. A stage structure
> > > > > > > describes the configuration for a mixer pair. So only one stage is needed
> > > > > > > for current usage cases. The quad-pipe case will be added in future and 2
> > > > > > > stages are used in the case. So extend the stage to an array with array size
> > > > > > > STAGES_PER_PLANE and blend pipes per mixer pair with configuration in the
> > > > > > > stage structure.
> > > > > > >
> > > > > > > Signed-off-by: Jun Nie <jun.nie@xxxxxxxxxx>
> > > > > > > ---
> > > > > > > drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 45 +++++++++++++++++++----------
> > > > > > > drivers/gpu/drm/msm/disp/dpu1/dpu_hw_mdss.h | 1 +
> > > > > > > 2 files changed, 30 insertions(+), 16 deletions(-)
> > > > > > >
> > > > > > > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> > > > > > > index 81474823e6799132db71c9712046d359e3535d90..50acaf25a3ffcc94354faaa816fe74566784844c 100644
> > > > > > > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> > > > > > > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> > > > > > > @@ -401,7 +401,7 @@ static void _dpu_crtc_blend_setup_pipe(struct drm_crtc *crtc,
> > > > > > > struct dpu_hw_stage_cfg *stage_cfg
> > > > > > > )
> > > > > > > {
> > > > > > > - uint32_t lm_idx;
> > > > > > > + uint32_t lm_idx, lm_in_pair;
> > > > > > > enum dpu_sspp sspp_idx;
> > > > > > > struct drm_plane_state *state;
> > > > > > >
> > > > > > > @@ -426,7 +426,8 @@ static void _dpu_crtc_blend_setup_pipe(struct drm_crtc *crtc,
> > > > > > > stage_cfg->multirect_index[stage][stage_idx] = pipe->multirect_index;
> > > > > > >
> > > > > > > /* blend config update */
> > > > > > > - for (lm_idx = 0; lm_idx < num_mixers; lm_idx++)
> > > > > > > + lm_in_pair = num_mixers > 1 ? 2 : 1;
> > > > > > > + for (lm_idx = 0; lm_idx < lm_in_pair; lm_idx++)
> > > > > > > mixer[lm_idx].lm_ctl->ops.update_pending_flush_sspp(mixer[lm_idx].lm_ctl, sspp_idx);
> > > > > >
> > > > > > I almost missed this. Why is this necessary?
> > > > >
> > > > > It is protective code. In case there is only 1 LM, we should not
> > > > > iterate 2 LM in a stage.
> > > >
> > > > That's not what the code does.
> > >
> > > I do not get your iea. _dpu_crtc_blend_setup_pipe() is called with
> > > num_mixers set as:
> > > cstate->num_mixers - (stage * PIPES_PER_STAGE).
> > > So lm_in_pair will get the LM number in this stage to iterate.
> >
> > You have written that it is incorrect to iterate over two LMs if we have
> > one. The code does a different thing: 'don't iterate over more than two
> > LMs'. It would be more idiomatic to write it as:
> >
> > lm_in_pair = min(num_mixers, 2);
> >
> > And then it is obvious that it is not 'lm_in_pair' (note, singular), but
> > something like 'lms_in_stage'. I'd really ask you to pull this up to a
> > caller function and pass a correct num_mixers instead.
>
> Thanks for the suggestion! min() is much more readable than mine version. And
> stage is more proper than LM pair as a stage may only contain one LM. Will
> replace the term.
>
> For the pulling up to a caller, you mean the min(num_mixers, 2) here, right?

Yes, to _dpu_crtc_blend_setup_mixer(). And of course. use a proper define for 2.

>
> >
> > > >
> > > > > >
> > > > > > > }
> > > > > > >
> > > > > >
> > > > > > [...]
> > > > > >
> > > > > > > @@ -535,8 +543,13 @@ static void _dpu_crtc_blend_setup(struct drm_crtc *crtc)
> > > > > > > mixer[i].mixer_op_mode,
> > > > > > > ctl->idx - CTL_0);
> > > > > > >
> > > > > > > + /*
> > > > > > > + * call dpu_hw_ctl_setup_blendstage() to blend layers per stage cfg.
> > > > > > > + * There are 4 mixers at most. The first 2 are for the left half, and
> > > > > > > + * the later 2 are for the right half.
> > > > > > > + */
> > > > > >
> > > > > > The comment is invalid until you introduce quad pipe, currently there
> > > > > > are 2 mixers at most. However you can just say something like 'stage
> > > > > > data is shared between PIPES_PER_STAGE pipes'.
> > > > >
> > > > > Accepted.
> > > > > >
> > > > > > > ctl->ops.setup_blendstage(ctl, mixer[i].hw_lm->idx,
> > > > > > > - &stage_cfg);
> > > > > > > + &stage_cfg[i / PIPES_PER_STAGE]);
> > > > > > > }
> > > > > > > }
> > > > > > >
> > > > > > > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_mdss.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_mdss.h
> > > > > > > index 5f010d36672cc6440c69779908b315aab285eaf0..64e220987be5682f26d02074505c5474a547a814 100644
> > > > > > > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_mdss.h
> > > > > > > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_mdss.h
> > > > > > > @@ -34,6 +34,7 @@
> > > > > > > #define DPU_MAX_PLANES 4
> > > > > > > #endif
> > > > > > >
> > > > > > > +#define STAGES_PER_PLANE 2
> > > >
> > > > BTW, This should be 1 for now.
> > >
> > > Yeah, it can be added in the last patch.
> > > >
> > > > > > > #define PIPES_PER_PLANE 2
> > > > > > > #define PIPES_PER_STAGE 2
> > > > > > > #ifndef DPU_MAX_DE_CURVES
> > > > > > >
> > > > > > > --
> > > > > > > 2.34.1
> > > > > > >
> > > > > >
> > > > > > --
> > > > > > With best wishes
> > > > > > Dmitry
> > > >
> > > > --
> > > > With best wishes
> > > > Dmitry
> >
> > --
> > With best wishes
> > Dmitry



--
With best wishes
Dmitry