linux-kernel - Re: [PATCH v14 20/39] pwm: tegra: Add runtime PM and OPP support

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Message-ID: <CAPDyKFoa5eQTrNxyiFevUCWitUecX=hi=y7qv1dC2mqk0+0XBA@mail.gmail.com>
Date:   Fri, 29 Oct 2021 17:28:55 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Viresh Kumar <vireshk@...nel.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        Mikko Perttunen <mperttunen@...dia.com>,
        Lee Jones <lee.jones@...aro.org>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, Nishanth Menon <nm@...com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Michael Turquette <mturquette@...libre.com>,
        linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-pwm@...r.kernel.org,
        linux-mmc@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-clk@...r.kernel.org, David Heidelberg <david@...t.cz>
Subject: Re: [PATCH v14 20/39] pwm: tegra: Add runtime PM and OPP support

On Fri, 29 Oct 2021 at 17:20, Dmitry Osipenko <digetx@...il.com> wrote:
>
> 26.10.2021 01:40, Dmitry Osipenko пишет:
> > +     ret = devm_pm_runtime_enable(&pdev->dev);
> > +     if (ret)
> > +             return ret;
> > +
> > +     ret = devm_tegra_core_dev_init_opp_table_common(&pdev->dev);
> > +     if (ret)
> > +             return ret;
> > +
> > +     ret = pm_runtime_resume_and_get(&pdev->dev);
> > +     if (ret)
> > +             return ret;
> > +
> >       /* Set maximum frequency of the IP */
> > -     ret = clk_set_rate(pwm->clk, pwm->soc->max_frequency);
> > +     ret = dev_pm_opp_set_rate(pwm->dev, pwm->soc->max_frequency);
> >       if (ret < 0) {
> >               dev_err(&pdev->dev, "Failed to set max frequency: %d\n", ret);
> > -             return ret;
> > +             goto put_pm;
> >       }
> >
> >       /*
> > @@ -278,7 +294,7 @@ static int tegra_pwm_probe(struct platform_device *pdev)
> >       if (IS_ERR(pwm->rst)) {
> >               ret = PTR_ERR(pwm->rst);
> >               dev_err(&pdev->dev, "Reset control is not found: %d\n", ret);
> > -             return ret;
> > +             goto put_pm;
> >       }
> >
> >       reset_control_deassert(pwm->rst);
> > @@ -291,10 +307,15 @@ static int tegra_pwm_probe(struct platform_device *pdev)
> >       if (ret < 0) {
> >               dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
> >               reset_control_assert(pwm->rst);
> > -             return ret;
> > +             goto put_pm;
> >       }
> >
> > +     pm_runtime_put(&pdev->dev);
> > +
> >       return 0;
> > +put_pm:
> > +     pm_runtime_put_sync_suspend(&pdev->dev);
> > +     return ret;
> >  }
> >
> >  static int tegra_pwm_remove(struct platform_device *pdev)
> > @@ -305,20 +326,44 @@ static int tegra_pwm_remove(struct platform_device *pdev)
> >
> >       reset_control_assert(pc->rst);
> >
> > +     pm_runtime_force_suspend(&pdev->dev);
>
> I just noticed that RPM core doesn't reset RPM-enable count of a device
> on driver's unbind (pm_runtime_reinit). It was a bad idea to use
> devm_pm_runtime_enable() + pm_runtime_force_suspend() here, since RPM is
> disabled twice on driver's removal, and thus, RPM will never be enabled
> again.
>
> I'll fix it for PWM and other drivers in this series, in v15.

Good catch - and sorry for not spotting it while reviewing!

Maybe devm_pm_runtime_enable() isn't that useful after all? Should we
suggest to remove it so others don't fall into the same trap?

Kind regards
Uffe