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

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Message-ID: <4dc8a6bd-4072-ccbf-513b-221d286bd6d5@gmail.com>
Date:   Fri, 29 Oct 2021 19:29:05 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        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 Mailing List <linux-kernel@...r.kernel.org>,
        linux-tegra <linux-tegra@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux PWM List <linux-pwm@...r.kernel.org>,
        linux-mmc <linux-mmc@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        David Heidelberg <david@...t.cz>
Subject: Re: [PATCH v14 20/39] pwm: tegra: Add runtime PM and OPP support

29.10.2021 18:56, Rafael J. Wysocki пишет:
> On Fri, Oct 29, 2021 at 5:20 PM 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.
> 
> Well, for the record, IMV using pm_runtime_force_suspend() is
> generally a questionable idea.
> 

Please clarify why it's a questionable idea.