linux-kernel - Re: [PATCH v7 2/3] drm/msm/dpu: allow using two SSPP blocks for a single plane

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Message-ID: <CAA8EJpoLwOVN3MB70UkiPe-dRhFMBigpTYc2PMn+tXnD=LhoBg@mail.gmail.com>
Date: Thu, 12 Dec 2024 00:40:51 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Abhinav Kumar <quic_abhinavk@...cinc.com>
Cc: Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>, 
	Marijn Suijten <marijn.suijten@...ainline.org>, David Airlie <airlied@...il.com>, 
	Simona Vetter <simona@...ll.ch>, linux-arm-msm@...r.kernel.org, 
	dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 2/3] drm/msm/dpu: allow using two SSPP blocks for a
 single plane

On Thu, 12 Dec 2024 at 00:38, Abhinav Kumar <quic_abhinavk@...cinc.com> wrote:
>
>
>
> On 12/11/2024 2:24 PM, Dmitry Baryshkov wrote:
> > On Wed, Dec 11, 2024 at 01:51:51PM -0800, Abhinav Kumar wrote:
> >>
> >>
> >> On 11/29/2024 5:55 PM, Dmitry Baryshkov wrote:
> >>> Virtual wide planes give high amount of flexibility, but it is not
> >>> always enough:
> >>>
> >>> In parallel multirect case only the half of the usual width is supported
> >>> for tiled formats. Thus the whole width of two tiled multirect
> >>> rectangles can not be greater than max_linewidth, which is not enough
> >>> for some platforms/compositors.
> >>>
> >>> Another example is as simple as wide YUV plane. YUV planes can not use
> >>> multirect, so currently they are limited to max_linewidth too.
> >>>
> >>> Now that the planes are fully virtualized, add support for allocating
> >>> two SSPP blocks to drive a single DRM plane. This fixes both mentioned
> >>> cases and allows all planes to go up to 2*max_linewidth (at the cost of
> >>> making some of the planes unavailable to the user).
> >>>
> >>
> >> Overall looks so much cleaner after unification!
> >>
> >> One small nit below,
> >>
> >>
> >> You can still have,
> >>
> >> Reviewed-by: Abhinav Kumar <quic_abhinavk@...cinc.com>
> >>
> >> Note: we have started testing this series with sc7180 CrOS, and will report
> >> our findings/ give tested-by this week.
> >>
> >>
> >> <snip>
> >>
> >>> +static bool dpu_plane_try_multirect_parallel(struct dpu_sw_pipe *pipe, struct dpu_sw_pipe_cfg *pipe_cfg,
> >>> +                                        struct dpu_sw_pipe *r_pipe, struct dpu_sw_pipe_cfg *r_pipe_cfg,
> >>> +                                        struct dpu_hw_sspp *sspp, const struct msm_format *fmt,
> >>> +                                        uint32_t max_linewidth)
> >>> +{
> >>> +   r_pipe->sspp = NULL;
> >>> +
> >>> +   pipe->multirect_index = DPU_SSPP_RECT_SOLO;
> >>> +   pipe->multirect_mode = DPU_SSPP_MULTIRECT_NONE;
> >>> +
> >>> +   r_pipe->multirect_index = DPU_SSPP_RECT_SOLO;
> >>> +   r_pipe->multirect_mode = DPU_SSPP_MULTIRECT_NONE;
> >>> +
> >>
> >>
> >> There are two places where the multirect_index and multirect_mode are reset.
> >> Would it be better to just have a small api dpu_plane_reset_multirect() and
> >> do this there?
> >
> > I'm not sure, what's the benefit. We can add an API to reset one pipe
> > (to also be able to use it in _dpu_plane_atomic_disable()), but then
> > it's just deduplication for the sake of deduplication.
> >
>
> Yeah I was thinking something like
>
> dpu_plane_reset_multirect(pipe);
> dpu_plane_reset_multirect(r_pipe);
>
> But its only a minor benefit, hence as I wrote it as a nit. We can keep
> things as it is, if its unnecessary in your opinion.

Well, granted that I hope to be able to drop non-virtual planes after
a few releases, I don't think it makes real sense.


-- 
With best wishes
Dmitry