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From:   =?UTF-8?B?Q2zDqW1lbnQgUMOpcm9u?= <peron.clem@gmail.com>
Date:   Fri, 29 May 2020 14:45:05 +0200
Message-ID: <CAJiuCcfJnBxh6McsNLKJ=HegS6dCVNVOChCOrcPGWobU3G8KKg@mail.gmail.com>
Subject: Re: [PATCH 07/15] drm/panfrost: use device_property_present to check
 for OPP
To:     Steven Price <steven.price@arm.com>
Cc:     Rob Herring <robh@kernel.org>,
        Tomeu Vizoso <tomeu.vizoso@collabora.com>,
        Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>,
        Viresh Kumar <vireshk@kernel.org>, Nishanth Menon <nm@ti.com>,
        Stephen Boyd <sboyd@kernel.org>,
        Maxime Ripard <mripard@kernel.org>,
        Chen-Yu Tsai <wens@csie.org>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        linux-kernel <linux-kernel@vger.kernel.org>
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Hi Steven,

On Thu, 28 May 2020 at 15:22, Steven Price <steven.price@arm.com> wrote:
>
> On 10/05/2020 17:55, Cl=C3=A9ment P=C3=A9ron wrote:
> > Instead of expecting an error from dev_pm_opp_of_add_table()
> > do a simple device_property_present() check.
> >
> > Signed-off-by: Cl=C3=A9ment P=C3=A9ron <peron.clem@gmail.com>
>
> I'm not sure I understand why this is better. We seem to have more code
> to do roughly the same thing just with the hard-coded
> "operating-points-v2" name (if there's ever a 'v3' we'll then have to
> update this).
>
> Is the desire just to get an error on probe if the table is malformed?
> Have you hit this situation? If so this sounds like something which
> would be better fixed in the generic OPP code rather than Panfrost itself=
.

The idea was to avoid calling devfreq if there is no opp table.
But I think you're right we don't have to check for malformed
device-tree in the driver.

I will drop this patch,

Regards,
Clement


>
> Steve
>
> > ---
> >   drivers/gpu/drm/panfrost/panfrost_devfreq.c | 14 +++++++++-----
> >   1 file changed, 9 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.c b/drivers/gpu/=
drm/panfrost/panfrost_devfreq.c
> > index d9007f44b772..fce21c682414 100644
> > --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> > +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> > @@ -96,15 +96,19 @@ int panfrost_devfreq_init(struct panfrost_device *p=
fdev)
> >       struct thermal_cooling_device *cooling;
> >       struct panfrost_devfreq *pfdevfreq =3D &pfdev->pfdevfreq;
> >
> > -     ret =3D dev_pm_opp_of_add_table(dev);
> > -     if (ret =3D=3D -ENODEV) /* Optional, continue without devfreq */
> > +     if (!device_property_present(dev, "operating-points-v2"))
> > +             /* Optional, continue without devfreq */
> >               return 0;
> > -     else if (ret)
> > -             return ret;
> > -     pfdevfreq->opp_of_table_added =3D true;
> >
> >       spin_lock_init(&pfdevfreq->lock);
> >
> > +     ret =3D dev_pm_opp_of_add_table(dev);
> > +     if (ret) {
> > +             DRM_DEV_ERROR(dev, "Couldn't add OPP table\n");
> > +             goto err_fini;
> > +     }
> > +     pfdevfreq->opp_of_table_added =3D true;
> > +
> >       panfrost_devfreq_reset(pfdevfreq);
> >
> >       cur_freq =3D clk_get_rate(pfdev->clock);
> >
>