linux-kernel - Re: [PATCH] ASoC: tlv320aic31xx: Remove regulator notification handling

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Date:   Tue, 4 Sep 2018 10:55:05 -0500
From:   "Andrew F. Davis" <afd@...com>
To:     Mark Brown <broonie@...nel.org>
CC:     Liam Girdwood <lgirdwood@...il.com>, <alsa-devel@...a-project.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ASoC: tlv320aic31xx: Remove regulator notification
 handling

On 09/04/2018 10:49 AM, Mark Brown wrote:
> On Tue, Sep 04, 2018 at 10:03:40AM -0500, Andrew F. Davis wrote:
>> On 09/04/2018 09:57 AM, Mark Brown wrote:
> 
>>> It's there to save us having to rewrite the register cache if we asked
>>> for the device to be powered down but that didn't actually happen due to
>>> other constraints, we know all the registers are still as we left them.
> 
>> I don't see that happening for any other user of this, we will still
>> have to re-write the cache when the device goes from OFF->STANDBY, and
> 
> You will?  All the power_off() code seems to do is mark the regmap as
> cache only and turn off the regulators.
> 

OFF->STANDBY will call power_on(). That is what is needed to start back
up after a regulator notification event.

>> if it stays in standby and never went off, then we are still broken as
>> we switched to using the register cache only, but never turned on real
>> writes again.
> 
> regmap can remember which registers were written to while in cache only
> mode and only sync the ones that are actually dirty, or you can
> invalidate the entire cache.
> 

If we never turn off cache only after a regulator notification then that
doesn't matter.