linux-kernel - Re: [PATCH 9/9] ASoC: cs35l41: Use devm_pm_runtime

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Date:   Tue, 5 Sep 2023 22:15:46 +0300
From:   Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
To:     Charles Keepax <ckeepax@...nsource.cirrus.com>
Cc:     James Schulman <james.schulman@...rus.com>,
        David Rhodes <david.rhodes@...rus.com>,
        Richard Fitzgerald <rf@...nsource.cirrus.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Stefan Binding <sbinding@...nsource.cirrus.com>,
        alsa-devel@...a-project.org, patches@...nsource.cirrus.com,
        linux-kernel@...r.kernel.org, kernel@...labora.com
Subject: Re: [PATCH 9/9] ASoC: cs35l41: Use devm_pm_runtime_enable()

On 9/5/23 12:45, Charles Keepax wrote:
> On Sun, Sep 03, 2023 at 12:06:21AM +0300, Cristian Ciocaltea wrote:
>> Simplify runtime PM during probe by converting pm_runtime_enable() to
>> the managed version.
>>
>> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
>> ---
>> @@ -1376,7 +1379,6 @@ void cs35l41_remove(struct cs35l41_private *cs35l41)
>>  	cancel_work_sync(&cs35l41->mdsync_up_work);
>>  
>>  	pm_runtime_get_sync(cs35l41->dev);
>> -	pm_runtime_disable(cs35l41->dev);
>>  
>>  	regmap_write(cs35l41->regmap, CS35L41_IRQ1_MASK1, 0xFFFFFFFF);
>>  	if (cs35l41->hw_cfg.bst_type == CS35L41_SHD_BOOST_PASS ||
> 
> Are we sure this is safe? The remove handler appears to be
> written to disable pm_runtime at the start presumably to stop the
> resume/suspend handler running during the remove callback.
> Whereas after this change the pm_runtime isn't disabled until
> after the remove callback has run. Does this open a window were
> we could get an erroneous pm_runtime suspend after the
> pm_runtime_put_noidle?

I've just made a test adding a 6s sleep before returning from the remove 
handler: 

[14444.894316] cs35l41 spi-VLV1776:00: Runtime resume
[14444.894469] cs35l41 spi-VLV1776:00: sleep 6s before return of cs35l41_remove()
[14448.338994] cs35l41 spi-VLV1776:00: Runtime suspend
[14451.079649] cs35l41 spi-VLV1776:00: return from cs35l41_remove()
[14451.080129] cs35l41 spi-VLV1776:00: Runtime resume
[14451.080165] cs35l41 spi-VLV1776:00: ASoC: Unregistered DAI 'cs35l41-pcm'
[14451.080181] cs35l41 spi-VLV1776:00: Runtime suspend
[14451.813639] acp5x_i2s_playcap acp5x_i2s_playcap.0: ASoC: Unregistered DAI 'acp5x_i2s_playcap.0'

As expected, suspend triggered, but a resume was issued later, before DAI
got unregistered.

I didn't notice any issues while repeating the test several times, hence 
I wonder what would be the reason to prevent getting suspend/resume events 
at this point?

Thanks,
Cristian