linux-kernel - Re: [PATCH] drm/msm/dpu: filter out too wide modes if no 3dmux is present

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Message-ID: <CAA8EJpojwG+_Q_9GYBFzQ_ReDbnO=+GbTPZscWgS1f=fkU0Anw@mail.gmail.com>
Date: Tue, 10 Dec 2024 00:16:43 +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] drm/msm/dpu: filter out too wide modes if no 3dmux is present

Hi Abhinav,

On Mon, 9 Dec 2024 at 22:07, Abhinav Kumar <quic_abhinavk@...cinc.com> wrote:
>
>
>
> On 12/7/2024 9:29 PM, Dmitry Baryshkov wrote:
> > On Fri, Dec 06, 2024 at 12:00:53PM -0800, Abhinav Kumar wrote:
> >> On chipsets such as QCS615, there is no 3dmux present. In such
> >> a case, a layer exceeding the max_mixer_width cannot be split,
> >> hence cannot be supported.
> >>
> >> Filter out the modes which exceed the max_mixer_width when there
> >> is no 3dmux present. Also, add a check in the dpu_crtc_atomic_check()
> >> to return failure for such modes.
> >>
> >> Signed-off-by: Abhinav Kumar <quic_abhinavk@...cinc.com>
> >> ---
> >> Note: this was only compile tested, so its pending validation on QCS615
> >> ---
> >>   drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 13 +++++++++++++
> >>   1 file changed, 13 insertions(+)
> >>
> >> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> >> index 9f6ffd344693ecfb633095772a31ada5613345dc..e6e5540aae83be7c20d8ae29115b8fdd42056e55 100644
> >> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> >> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> >> @@ -732,6 +732,13 @@ static int _dpu_crtc_check_and_setup_lm_bounds(struct drm_crtc *crtc,
> >>      struct dpu_kms *dpu_kms = _dpu_crtc_get_kms(crtc);
> >>      int i;
> >>
> >> +    /* if we cannot merge 2 LMs (no 3d mux) better to fail earlier
> >> +     * before even checking the width after the split
> >> +     */
> >> +    if (!dpu_kms->catalog->caps->has_3d_merge
> >> +        && adj_mode->hdisplay > dpu_kms->catalog->caps->max_mixer_width)
> >> +            return -E2BIG;
> >
> > Is it the same as checking that there are LMs which support
> > DPU_MIXER_SOURCESPLIT ?
> >
>
> DPU_MIXER_SOURCESPLIT tells whether we can have more than one SSPP in
> the same blend stage.

Do we have a feature bit that corresponds to the ability to use 2 LMs?
I mean, there are other *split topologies, not necessarily the 3DMux
ones. E.g. PPSPLIT.

>
> 494     if (test_bit(DPU_MIXER_SOURCESPLIT,
> 495             &ctx->mixer_hw_caps->features))
> 496             pipes_per_stage = PIPES_PER_STAGE;
> 497     else
> 498             pipes_per_stage = 1;
>
> That is different from this one. Here we are checking if we can actually
> blend two LM outputs using the 3dmux (so its post blend).
>
> >> +
> >>      for (i = 0; i < cstate->num_mixers; i++) {
> >>              struct drm_rect *r = &cstate->lm_bounds[i];
> >>              r->x1 = crtc_split_width * i;
> >> @@ -1251,6 +1258,12 @@ static enum drm_mode_status dpu_crtc_mode_valid(struct drm_crtc *crtc,
> >>   {
> >>      struct dpu_kms *dpu_kms = _dpu_crtc_get_kms(crtc);
> >>
> >> +    /* if there is no 3d_mux block we cannot merge LMs so we cannot
> >> +     * split the large layer into 2 LMs, filter out such modes
> >> +     */
> >> +    if (!dpu_kms->catalog->caps->has_3d_merge
> >> +        && mode->hdisplay > dpu_kms->catalog->caps->max_mixer_width)
> >> +            return MODE_BAD;
> >
> > This can be more specific, like MODE_BAD_HVALUE.
> >
>
> Yes for sure, will fix this up.
>
> >>      /*
> >>       * max crtc width is equal to the max mixer width * 2 and max height is 4K
> >>       */
> >>
> >> ---
> >> base-commit: af2ea8ab7a546b430726183458da0a173d331272
> >> change-id: 20241206-no_3dmux-521a55ea0669
> >>
> >> Best regards,
> >> --
> >> Abhinav Kumar <quic_abhinavk@...cinc.com>
> >>
> >



-- 
With best wishes
Dmitry