linux-kernel - Re: [PATCH v16 21/40] pwm: tegra: Add runtime PM and OPP support

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Date:   Mon, 21 Feb 2022 14:37:24 +0100
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Dmitry Osipenko <digetx@...il.com>
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>, 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 v16 21/40] pwm: tegra: Add runtime PM and OPP support

Hello,

On Mon, Feb 21, 2022 at 12:53:58PM +0300, Dmitry Osipenko wrote:
> 21.02.2022 11:17, Uwe Kleine-König пишет:
> >> @@ -344,7 +387,10 @@ static const struct of_device_id tegra_pwm_of_match[] = {
> >>  MODULE_DEVICE_TABLE(of, tegra_pwm_of_match);
> >>  
> >>  static const struct dev_pm_ops tegra_pwm_pm_ops = {
> >> -	SET_SYSTEM_SLEEP_PM_OPS(tegra_pwm_suspend, tegra_pwm_resume)
> >> +	SET_RUNTIME_PM_OPS(tegra_pwm_runtime_suspend, tegra_pwm_runtime_resume,
> >> +			   NULL)
> >> +	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
> >> +				pm_runtime_force_resume)
> >>  };
> >>  
> >>  static struct platform_driver tegra_pwm_driver = {
> > I admit to not completely understand the effects of this patch, but I
> > don't see a problem either. So for me this patch is OK:
> > 
> > Acked-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> > 
> > I spot a problem, it's not introduced by this patch however: If the
> > consumer of the PWM didn't stop the hardware, the suspend should IMHO be
> > prevented.
> 
> Why? The PWM driver itself will stop the h/w on suspend.

Stopping the PWM might be bad. Only the consumer can know if it's ok to
stop the PWM on suspend. If so the consumer should stop the PWM in their
suspend callback and the PWM should prevent suspend if it wasn't
stopped.

> > I wonder if the patches in this series go in in one go via an ARM or
> > Tegra tree, or each patch via its respective maintainer tree.
> 
> This series, including this patch, was already applied to 5.17 via the
> tegra/soc tree. No action is needed anymore.

Ah, I missed that, thanks.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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