linux-kernel - Re: [PATCH v4 00/79] Address some issues with PM runtime at media subsystem

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Message-ID: <de636a0a-3fd7-d61e-c361-fa50a6d34f17@gmail.com>
Date:   Thu, 29 Apr 2021 15:33:59 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Johan Hovold <johan@...nel.org>
Cc:     Shawn Tu <shawnx.tu@...el.com>,
        Ricardo Ribalda <ribalda@...nel.org>,
        Dafna Hirschfeld <dafna.hirschfeld@...labora.com>,
        Heiko Stuebner <heiko@...ech.de>, linuxarm@...wei.com,
        Todor Tomov <todor.too@...il.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
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        Thierry Reding <thierry.reding@...il.com>,
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        Leon Luo <leonl@...pardimaging.com>,
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Subject: Re: [PATCH v4 00/79] Address some issues with PM runtime at media
 subsystem

29.04.2021 13:18, Mauro Carvalho Chehab пишет:
>> This is perfectly alright. Take a look at ov7740_remove() for example:
>>
>> 	pm_runtime_get_sync(&client->dev);
>> 	pm_runtime_disable(&client->dev);
>> 	pm_runtime_set_suspended(&client->dev);
>> 	pm_runtime_put_noidle(&client->dev);
>> 	
>> 	ov7740_set_power(ov7740, 0);
>>
>> There's an explicit power-off after balancing the PM count and this will
>> work regardless of the power state when entering this function.
> Ok, but this should equally work:
> 
>  	pm_runtime_disable(&client->dev);
>  	pm_runtime_set_suspended(&client->dev);
>  	
>  	ov7740_set_power(ov7740, 0);
> 
> as there's no additional cleanup made on this particular driver
> between pm_runtime_get_sync() and pm_runtime_put_noidle().
> 

The pm_runtime_get_sync() turns hardware ON by invoking
ov7740_set_power(ov7740, 1), and thus, the ON->OFF is kept balanced in
both RPM-available and RPM-unavailable cases. The RPM state of device
should be reset after driver removal.

It doesn't look like any additional cleanups are needed by that ov7740
driver. The driver removal is opposite to the probe, hence it should be
correct as-is.