linux-kernel - Re: [PATCH v13 13/35] drm/tegra: gr2d: Support generic power domain and runtime PM

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Date:   Fri, 1 Oct 2021 17:29:00 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
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>,
        Peter Chen <peter.chen@...nel.org>,
        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 USB List <linux-usb@...r.kernel.org>,
        linux-staging@...ts.linux.dev, linux-pwm@...r.kernel.org,
        linux-mmc <linux-mmc@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        DTML <devicetree@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        Mark Brown <broonie@...nel.org>,
        Vignesh Raghavendra <vigneshr@...com>,
        Richard Weinberger <richard@....at>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Lucas Stach <dev@...xeye.de>, Stefan Agner <stefan@...er.ch>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        David Heidelberg <david@...t.cz>
Subject: Re: [PATCH v13 13/35] drm/tegra: gr2d: Support generic power domain
 and runtime PM

01.10.2021 16:39, Ulf Hansson пишет:
> On Mon, 27 Sept 2021 at 00:42, Dmitry Osipenko <digetx@...il.com> wrote:
>>
>> Add runtime power management and support generic power domains.
>>
>> Tested-by: Peter Geis <pgwipeout@...il.com> # Ouya T30
>> Tested-by: Paul Fertser <fercerpav@...il.com> # PAZ00 T20
>> Tested-by: Nicolas Chauvet <kwizart@...il.com> # PAZ00 T20 and TK1 T124
>> Tested-by: Matt Merhar <mattmerhar@...tonmail.com> # Ouya T30
>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>> ---
>>  drivers/gpu/drm/tegra/gr2d.c | 155 +++++++++++++++++++++++++++++++++--
> 
> [...]
> 
>>  static int gr2d_remove(struct platform_device *pdev)
>> @@ -259,15 +312,101 @@ static int gr2d_remove(struct platform_device *pdev)
>>                 return err;
>>         }
>>
>> +       pm_runtime_dont_use_autosuspend(&pdev->dev);
>> +       pm_runtime_disable(&pdev->dev);
> 
> There is no guarantee that the ->runtime_suspend() has been invoked
> here, which means that clock may be left prepared/enabled beyond this
> point.
> 
> I suggest you call pm_runtime_force_suspend(), instead of
> pm_runtime_disable(), to make sure that gets done.

The pm_runtime_disable() performs the final synchronization, please see [1].

[1]
https://elixir.bootlin.com/linux/v5.15-rc3/source/drivers/base/power/runtime.c#L1412

Calling pm_runtime_force_suspend() isn't correct because each 'enable'
must have the corresponding 'disable'. Hence there is no problem here.