linux-kernel - Re: [PATCH AUTOSEL 5.7 055/388] ASoC: SOF: Do nothing when DSP PM callbacks are not set

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Message-ID: <1d1041f9-521b-98f5-a6ef-12d43615bc13@nxp.com>
Date:   Thu, 18 Jun 2020 14:44:18 +0300
From:   Daniel Baluta <daniel.baluta@....com>
To:     Mark Brown <broonie@...nel.org>, Sasha Levin <sashal@...nel.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        sound-open-firmware@...a-project.org, alsa-devel@...a-project.org
Subject: Re: [PATCH AUTOSEL 5.7 055/388] ASoC: SOF: Do nothing when DSP PM
 callbacks are not set

On 6/18/20 2:01 PM, Mark Brown wrote:
> On Wed, Jun 17, 2020 at 09:02:32PM -0400, Sasha Levin wrote:
>> From: Daniel Baluta <daniel.baluta@....com>
>>
>> [ Upstream commit c26fde3b15ed41f5f452f1da727795f787833287 ]
>>
>> This provides a better separation between runtime and PM sleep
>> callbacks.
>>
>> Only do nothing if given runtime flag is set and calback is not set.
>>
>> With the current implementation, if PM sleep callback is set but runtime
>> callback is not set then at runtime resume we reload the firmware even
>> if we do not support runtime resume callback.
> This doesn't look like a bugfix, just an optimization?

Indeed can be seen as an optimization, but it does unexpected things 
which can cause trouble

and weird behavior for people not familiar with the matter.

For example, as explained in the commit message if you only provide

System PM handler but not runtime PM handler, then the DSP will be resetted

even if this is not the intention.