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

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Message-ID: <CAN5H-g4zEkxrUr2_0QZfNHndVqF=L-Bx3OTbKnFjQVmoYc7FyQ@mail.gmail.com>
Date:   Mon, 22 May 2023 11:30:02 +0200
From:   Arnaud Vrac <rawoul@...il.com>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     Jeykumar Sankaran <quic_jeykumar@...cinc.com>,
        Arnaud Vrac <avrac@...ebox.fr>,
        Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>, linux-arm-msm@...r.kernel.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [Freedreno] [PATCH 02/11] drm/msm/dpu: use the actual lm maximum
 width instead of a hardcoded value

Le sam. 20 mai 2023 à 22:49, Dmitry Baryshkov
<dmitry.baryshkov@...aro.org> a écrit :
>
> 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@...ebox.fr>
> >>
> >> 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.

It's fine, if I remember correctly I wrote this patch because display
wouldn't work before I fixed the LM pairings on msm8998, but now it's
not a requirement anymore.

>
> >
> > 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
>