linux-kernel - Re: [PATCH 07/15] drm/panfrost: use device_property

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Date:   Fri, 29 May 2020 14:45:05 +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>,
        Maxime Ripard <mripard@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 07/15] drm/panfrost: use device_property_present to check
 for OPP

Hi Steven,

On Thu, 28 May 2020 at 15:22, Steven Price <steven.price@....com> wrote:
>
> On 10/05/2020 17:55, Clément Péron wrote:
> > Instead of expecting an error from dev_pm_opp_of_add_table()
> > do a simple device_property_present() check.
> >
> > Signed-off-by: Clément Péron <peron.clem@...il.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 *pfdev)
> >       struct thermal_cooling_device *cooling;
> >       struct panfrost_devfreq *pfdevfreq = &pfdev->pfdevfreq;
> >
> > -     ret = dev_pm_opp_of_add_table(dev);
> > -     if (ret == -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 = true;
> >
> >       spin_lock_init(&pfdevfreq->lock);
> >
> > +     ret = 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 = true;
> > +
> >       panfrost_devfreq_reset(pfdevfreq);
> >
> >       cur_freq = clk_get_rate(pfdev->clock);
> >
>