linux-kernel - Re: [Freedreno] [PATCH 5/6] drm: msm: a6xx: use dev_pm_opp_set_bw to set DDR bandwidth

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Message-ID: <CAF6AEGtoNwUGX-r7QytGn5hSU-VD4RJZyhcb3WdgAgAFR5BK4A@mail.gmail.com>
Date:   Mon, 18 May 2020 09:25:41 -0700
From:   Rob Clark <robdclark@...il.com>
To:     Sharat Masetty <smasetty@...eaurora.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, dri-devel@...edesktop.org,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Georgi Djakov <georgi.djakov@...aro.org>,
        Matthias Kaehlcke <mka@...omium.org>
Subject: Re: [Freedreno] [PATCH 5/6] drm: msm: a6xx: use dev_pm_opp_set_bw to
 set DDR bandwidth

On Mon, May 18, 2020 at 7:23 AM Jordan Crouse <jcrouse@...eaurora.org> wrote:
>
> On Thu, May 14, 2020 at 04:24:18PM +0530, Sharat Masetty wrote:
> > This patches replaces the previously used static DDR vote and uses
> > dev_pm_opp_set_bw() to scale GPU->DDR bandwidth along with scaling
> > GPU frequency.
> >
> > Signed-off-by: Sharat Masetty <smasetty@...eaurora.org>
> > ---
> >  drivers/gpu/drm/msm/adreno/a6xx_gmu.c | 6 +-----
> >  1 file changed, 1 insertion(+), 5 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> > index 2d8124b..79433d3 100644
> > --- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> > +++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> > @@ -141,11 +141,7 @@ void a6xx_gmu_set_freq(struct msm_gpu *gpu, struct dev_pm_opp *opp)
> >
> >       gmu->freq = gmu->gpu_freqs[perf_index];
> >
> > -     /*
> > -      * Eventually we will want to scale the path vote with the frequency but
> > -      * for now leave it at max so that the performance is nominal.
> > -      */
> > -     icc_set_bw(gpu->icc_path, 0, MBps_to_icc(7216));
> > +     dev_pm_opp_set_bw(&gpu->pdev->dev, opp);
> >  }
>
> This adds an implicit requirement that all targets need bandwidth settings
> defined in the OPP or they won't get a bus vote at all. I would prefer that
> there be an default escape valve but if not you'll need to add
> bandwidth values for the sdm845 OPP that target doesn't regress.
>

it looks like we could maybe do something like:

  ret = dev_pm_opp_set_bw(...);
  if (ret) {
      dev_warn_once(dev, "no bandwidth settings");
      icc_set_bw(...);
  }

?

BR,
-R

> Jordan
>
> >  unsigned long a6xx_gmu_get_freq(struct msm_gpu *gpu)
> > --
> > 2.7.4
> >
>
> --
> The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
> a Linux Foundation Collaborative Project
> _______________________________________________
> Freedreno mailing list
> Freedreno@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/freedreno

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