linux-kernel - Re: [PATCH] regulator: Lookup unresolved parent supplies before regulators cleanup

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Date:	Mon, 21 Mar 2016 09:25:26 -0300
From:	Javier Martinez Canillas <javier@....samsung.com>
To:	Mark Brown <broonie@...nel.org>
Cc:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Liam Girdwood <lgirdwood@...il.com>,
	Bjorn Andersson <bjorn.andersson@...aro.org>
Subject: Re: [PATCH] regulator: Lookup unresolved parent supplies before
 regulators cleanup


On 03/21/2016 09:13 AM, Javier Martinez Canillas wrote:
> [adding Bjorn Andersson who is the author of commit 6261b06de565]
>

I got a user invalid error when sending to the email address that Bjorn used
in that commit, so I'm re-sending to his latest address. Sorry for the spam.

Bjorn, here is the email archive in case you need more context:

https://lkml.org/lkml/2016/3/20/277
 
> Hello Mark,
> 
> Thanks a lot for your feedback.
> 
> On 03/21/2016 08:11 AM, Mark Brown wrote:
>> On Sun, Mar 20, 2016 at 11:39:46PM -0300, Javier Martinez Canillas wrote:
>>
>>> Unfortunately, that changed the behavior of the regulator core since now a
>>> parent supply with a child regulator marked as always-on, won't be enabled
>>> unless a client driver attempts to get the child regulator during boot.
>>
>>> This patch makes the unresolved parent supplies to be looked up before the
>>> regulators late cleanup, so those with a child marked as always on will be
>>> enabled regardless if a driver attempted to get the child regulator or not.
>>
>> This doesn't make much sense to me as a fix - it feels like we're doing
>> a fragile hack.  Surely it's better to do this as we register the
>> devices, that way we're also protected against any similar issues with
> 
> Sorry, not sure if I understood correctly. You mean to do it when the
> drivers register the regulators, so at regulator_register() ?
> 
> That's basically what was done before Bjorn's patch but that doesn't
> handle the case of out of order registration when having circular
> dependencies between regulators.
> 
>> this that might occur after late probe if things are built modular?  Or
> 
> Someone told me once that modules are always a special case :)
> 
>> is there a strong reason for doing this only at late_initcall?
>>
> 
> The reason why I did in late_initcall / regulator_init_complete is that
> the problem for me is that unused regulators are disabled on cleanup but
> parents whose childrens are marked as always on should be keep enabled.
> 
> But these are disabled anyways just because the regulator core didn't know
> about that dependency. So doing it before the late cleanup sounded like a
> good solution for me.
> 
> Now if you think that's a hack and have another approach in mind, then I'll
> gladly try to implement it instead, if you could please elaborate on that.
> 

Best regards,
-- 
Javier Martinez Canillas
Open Source Group
Samsung Research America