Re: [Freedreno] [PATCH 02/11] drm/msm/dpu: use the actual lm maximum width instead of a hardcoded value

[Dmitry Baryshkov]

On 20/04/2023 20:47, Jeykumar Sankaran wrote:
> On 4/19/2023 3:23 PM, Dmitry Baryshkov wrote:
> > On 19/04/2023 17:41, Arnaud Vrac wrote:
> > > This avoids using two LMs instead of one when the display width is lower
> > > than the maximum supported value. For example on MSM8996/MSM8998, the
> > > actual maxwidth is 2560, so we would use two LMs for 1280x720 or
> > > 1920x1080 resolutions, while one is enough.
> > >
> > > Signed-off-by: Arnaud Vrac <avrac@xxxxxxxxxx>
> >
> > While this looks correct (and following what we have in 4.4), later 
> > vendor kernels specify the topology explicitly. Probably we should 
> > check this with the hw guys, because it might be the following case: 
> > even though a single LM can supply the mode, it will spend more power 
> > compared to two LMs.
> Yes. 2 LM split will allow the HW to run in lower mdp core clock. Can 
> you maintain the split_threshold in the hw catalog until per mode 
> topology is available?

I don't think it warrants the trouble, unless we have a real usecase 
when the device is short of LMs.

Arnaud, I'll mark this patch as Rejected for now, unless it fixes an LM 
shortage for your platform.

> Jeykumar S
> > > ---
> > >   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 10 +++++-----
> > >   1 file changed, 5 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c 
> > > b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> > > index 1dc5dbe585723..dd2914726c4f6 100644
> > > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> > > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> > > @@ -53,8 +53,6 @@
> > >   #define IDLE_SHORT_TIMEOUT    1
> > > -#define MAX_HDISPLAY_SPLIT 1080
> > > -
> > >   /* timeout in frames waiting for frame done */
> > >   #define DPU_ENCODER_FRAME_DONE_TIMEOUT_FRAMES 5
> > > @@ -568,10 +566,12 @@ static struct msm_display_topology 
> > > dpu_encoder_get_topology(
> > >        */
> > >       if (intf_count == 2)
> > >           topology.num_lm = 2;
> > > -    else if (!dpu_kms->catalog->caps->has_3d_merge)
> > > -        topology.num_lm = 1;
> > > +    else if (dpu_kms->catalog->caps->has_3d_merge &&
> > > +         dpu_kms->catalog->mixer_count > 0 &&
> > > +         mode->hdisplay > dpu_kms->catalog->mixer[0].sblk->maxwidth)
> > > +        topology.num_lm = 2;
> > >       else
> > > -        topology.num_lm = (mode->hdisplay > MAX_HDISPLAY_SPLIT) ? 2 
> > > : 1;
> > > +        topology.num_lm = 1;
> > >       if (crtc_state->ctm)
> > >           topology.num_dspp = topology.num_lm;

--
With best wishes
Dmitry