linux-kernel - Re: [PATCH 58/78] media: exynos-gsc: use pm_runtime_resume_and

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Message-ID: <5f6088c7-c839-f097-737f-b4234c413eac@samsung.com>
Date:   Tue, 27 Apr 2021 13:50:44 +0200
From:   Sylwester Nawrocki <s.nawrocki@...sung.com>
To:     Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
Cc:     linuxarm@...wei.com, mauro.chehab@...wei.com,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-media@...r.kernel.org, linux-samsung-soc@...r.kernel.org
Subject: Re: [PATCH 58/78] media: exynos-gsc: use
 pm_runtime_resume_and_get()

On 27.04.2021 11:42, Mauro Carvalho Chehab wrote:
> Em Tue, 27 Apr 2021 11:30:55 +0200
> Mauro Carvalho Chehab <mchehab+huawei@...nel.org> escreveu:
> 
>> Em Tue, 27 Apr 2021 10:18:12 +0200
>> Sylwester Nawrocki <s.nawrocki@...sung.com> escreveu:
>>
>>> On 24.04.2021 08:45, Mauro Carvalho Chehab wrote:  
>>>> Commit dd8088d5a896 ("PM: runtime: Add pm_runtime_resume_and_get to deal with usage counter")
>>>> added pm_runtime_resume_and_get() in order to automatically handle
>>>> dev->power.usage_count decrement on errors.
>>>>
>>>> Use the new API, in order to cleanup the error check logic.
>>>>
>>>> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
>>>> ---
>>>>  drivers/media/platform/exynos-gsc/gsc-core.c | 3 +--
>>>>  drivers/media/platform/exynos-gsc/gsc-m2m.c  | 2 +-
>>>>  2 files changed, 2 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/media/platform/exynos-gsc/gsc-core.c b/drivers/media/platform/exynos-gsc/gsc-core.c
>>>> index 9f41c2e7097a..9d5841194f6b 100644
>>>> --- a/drivers/media/platform/exynos-gsc/gsc-core.c
>>>> +++ b/drivers/media/platform/exynos-gsc/gsc-core.c
>>>> @@ -1210,7 +1210,7 @@ static int gsc_remove(struct platform_device *pdev)
>>>>  	struct gsc_dev *gsc = platform_get_drvdata(pdev);
>>>>  	int i;
>>>>  
>>>> -	pm_runtime_get_sync(&pdev->dev);
>>>> +	pm_runtime_resume_and_get(&pdev->dev);
>>>>  
>>>>  	gsc_unregister_m2m_device(gsc);
>>>>  	v4l2_device_unregister(&gsc->v4l2_dev);
>>>> @@ -1219,7 +1219,6 @@ static int gsc_remove(struct platform_device *pdev)
>>>>  	for (i = 0; i < gsc->num_clocks; i++)
>>>>  		clk_disable_unprepare(gsc->clock[i]);
>>>>  
>>>> -	pm_runtime_put_noidle(&pdev->dev);    
>>>
>>> If we do this then the device usage count will not get decremented
>>> after the pm_runtime_resume_and_get() call above and after driver
>>> unload/load cycle it will not be possible to suspend the device.
>>> I wouldn't be changing anything in gsc_remove(), pm_runtime_get_sync()
>>> works better in that case.  
>>
>> Good point.
>>
>> Actually, I don't see any reason why to call a PM resume
>> function - either being pm_runtime_get_sync() or
>> pm_runtime_resume_and_get().
>>
>> The code there could simply be:
>>
>>     static int gsc_remove(struct platform_device *pdev)
>>     {
>>         struct gsc_dev *gsc = platform_get_drvdata(pdev);
>>         int i;
>>
>>         gsc_unregister_m2m_device(gsc);
>>         v4l2_device_unregister(&gsc->v4l2_dev);
>>
>>         vb2_dma_contig_clear_max_seg_size(&pdev->dev);
>>         for (i = 0; i < gsc->num_clocks; i++)
>>                 clk_disable_unprepare(gsc->clock[i]);
>>
>>         pm_runtime_disable(&pdev->dev);
>>
>>         dev_dbg(&pdev->dev, "%s driver unloaded\n", pdev->name);
>>         return 0;
>>     }
>>
>> Eventually also adding:
>> 	pm_runtime_suspended(&pdev->dev);
> 
> In time: I actually meant:
> 
> 	pm_runtime_set_suspended(&pdev->dev);
> 
> but after double-checking the PM runtime code, it sounds to me that
> just calling pm_runtime_disable() would be enough. Not 100% sure
> here. Btw, some media drivers call it after pm_runtime_disable(),
> while others don't do.

I think if the device is brought into suspended state (e.g. by
disabling clocks as above) the pm_runtime_set_suspended() call
should be there. IOW a following sequence: 

	pm_runtime_disable(dev);
	if (!pm_runtime_status_suspended(dev))
		/* put device into suspended state (disable clocks, 
		  voltage regulators, assert GPIOs, etc. */
	pm_runtime_set_suspended(dev);

--
Regards,
Sylwester