linux-kernel - Re: [PATCH 2/2] drm/panfrost: add devfreq regulator support

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Message-ID: <CAJiuCcegkNGQ7j4jcT1rBpSLqG1c-nb8g0wq+Nbvt-dGj7am2Q@mail.gmail.com>
Date:   Mon, 13 Apr 2020 16:18:32 +0200
From:   Clément Péron <peron.clem@...il.com>
To:     Steven Price <steven.price@....com>
Cc:     Rob Herring <robh@...nel.org>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Alyssa Rosenzweig <alyssa.rosenzweig@...labora.com>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] drm/panfrost: add devfreq regulator support

Hi Steven,

On Mon, 13 Apr 2020 at 15:18, Steven Price <steven.price@....com> wrote:
>
> On 11/04/2020 21:06, Clément Péron wrote:
> > OPP table can defined both frequency and voltage.
> >
> > Register the mali regulator if it exist.
> >
> > Signed-off-by: Clément Péron <peron.clem@...il.com>
> > ---
> >   drivers/gpu/drm/panfrost/panfrost_devfreq.c | 34 ++++++++++++++++++---
> >   drivers/gpu/drm/panfrost/panfrost_device.h  |  1 +
> >   2 files changed, 31 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.c b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> > index 62541f4edd81..2dc8e2355358 100644
> > --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> > +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> > @@ -78,12 +78,26 @@ int panfrost_devfreq_init(struct panfrost_device *pfdev)
> >       struct device *dev = &pfdev->pdev->dev;
> >       struct devfreq *devfreq;
> >       struct thermal_cooling_device *cooling;
> > +     const char *mali = "mali";
> > +     struct opp_table *opp_table = NULL;
> > +
> > +     /* Regulator is optional */
> > +     opp_table = dev_pm_opp_set_regulators(dev, &mali, 1);
>
> This looks like it applies before 3e1399bccf51 ("drm/panfrost: Add
> support for multiple regulators") which is currently in drm-misc-next
> (and linux-next). You want something more like:

Thanks for you review, indeed I didn't see that multiple regulators
support has been added.
Will update in v2.

>
>      opp_table = dev_pm_opp_set_regulators(dev,
>                                            pfdev->comp->supply_names,
>                                            pfdev->comp->num_supplies);
>
> Otherwise a platform with multiple regulators won't work correctly.
>
> Also running on my firefly (RK3288) board I get the following warning:
>
>     debugfs: Directory 'ffa30000.gpu-mali' with parent 'vdd_gpu' already
> present!
>
> This is due to the regulator debugfs entries getting created twice (once
> in panfrost_regulator_init() and once here).

Is it a warning that should be consider as an error? Look's more an info no?
What should be the correct behavior if a device want to register two
times the same regulator?

Link to original discussion:
https://lore.kernel.org/patchwork/patch/1176717/

Thanks,
Clement

>
> I have been taking a look at doing the same thing (I picked up Martin
> Blumenstingl's patch series[1]), but haven't had much time to focus on
> this recently.
>
> Thanks,
>
> Steve
>
> [1]
> https://lore.kernel.org/dri-devel/20200112001623.2121227-1-martin.blumenstingl@googlemail.com/
>
>
> > +     if (IS_ERR(opp_table)) {
> > +             ret = PTR_ERR(opp_table);
> > +             if (ret != -ENODEV) {
> > +                     DRM_DEV_ERROR(dev, "Failed to set regulator: %d\n", ret);
> > +                     return ret;
> > +             }
> > +     }
> > +     pfdev->devfreq.opp_table = opp_table;
> >
> >       ret = dev_pm_opp_of_add_table(dev);
> > -     if (ret == -ENODEV) /* Optional, continue without devfreq */
> > -             return 0;
> > -     else if (ret)
> > -             return ret;
> > +     if (ret) {
> > +             if (ret == -ENODEV) /* Optional, continue without devfreq */
> > +                     ret = 0;
> > +             goto err_opp_reg;
> > +     }
> >
> >       panfrost_devfreq_reset(pfdev);
> >
> > @@ -119,6 +133,12 @@ int panfrost_devfreq_init(struct panfrost_device *pfdev)
> >   err_opp:
> >       dev_pm_opp_of_remove_table(dev);
> >
> > +err_opp_reg:
> > +     if (pfdev->devfreq.opp_table) {
> > +             dev_pm_opp_put_regulators(pfdev->devfreq.opp_table);
> > +             pfdev->devfreq.opp_table = NULL;
> > +     }
> > +
> >       return ret;
> >   }
> >
> > @@ -126,7 +146,13 @@ void panfrost_devfreq_fini(struct panfrost_device *pfdev)
> >   {
> >       if (pfdev->devfreq.cooling)
> >               devfreq_cooling_unregister(pfdev->devfreq.cooling);
> > +
> >       dev_pm_opp_of_remove_table(&pfdev->pdev->dev);
> > +
> > +     if (pfdev->devfreq.opp_table) {
> > +             dev_pm_opp_put_regulators(pfdev->devfreq.opp_table);
> > +             pfdev->devfreq.opp_table = NULL;
> > +     }
> >   }
> >
> >   void panfrost_devfreq_resume(struct panfrost_device *pfdev)
> > diff --git a/drivers/gpu/drm/panfrost/panfrost_device.h b/drivers/gpu/drm/panfrost/panfrost_device.h
> > index 06713811b92c..f6b0c779dfe5 100644
> > --- a/drivers/gpu/drm/panfrost/panfrost_device.h
> > +++ b/drivers/gpu/drm/panfrost/panfrost_device.h
> > @@ -86,6 +86,7 @@ struct panfrost_device {
> >       struct {
> >               struct devfreq *devfreq;
> >               struct thermal_cooling_device *cooling;
> > +             struct opp_table *opp_table;
> >               ktime_t busy_time;
> >               ktime_t idle_time;
> >               ktime_t time_last_update;
> >
>