linux-kernel - Re: [PATCH] regulator: core: Keep boot

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Date:	Wed, 25 Apr 2012 11:37:36 +0200
From:	Ulf Hansson <ulf.hansson@...ricsson.com>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Cc:	Liam Girdwood <lrg@...mlogic.co.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Mattias WALLIN <mattias.wallin@...ricsson.com>,
	Jonas ABERG <jonas.aberg@...ricsson.com>,
	Lee Jones <lee.jones@...aro.org>
Subject: Re: [PATCH] regulator: core: Keep boot_on regulators powered during
 init

On 04/25/2012 10:02 AM, Mark Brown wrote:
> On Tue, Apr 24, 2012 at 02:43:20PM +0200, Ulf Hansson wrote:
>
>> So if grabbing a reference, there is no good point in the code were
>> I can drop it. Moreover _every_ host driver needs to handle this. It
>> will likely become a "hack" is my first impression.
>
> If it's something that every host driver needs to do then just factor it
> into the framework and we're done...  The stuff you're trying to put in
> the regulator API feels equally like it's a bodge and it seems to me
> like we've just not thought of the best way for the MMC stack to figure
> out and keep track of if it needs a regulator or not.
>
>>> This just seems awfully fragile and very much dependant on things like
>>> having the driver actually enabled to clean up later.
>
>> Setting this constraint is not done be "default", it could be
>> clearly be stated that the consumer must handle the enable/disable,
>> otherwise the regulator will be left in the state it was when the
>> kernel booted.
>
> Right, but the whole point in having full constraints is to avoid that.
> Users are supposed to set constraints to grant permissions for things,
> not to work around internal problems in the rest of the stack.  If I
> could see a general use case for the feature...  but I'm having trouble
> doing that.

Maybe you have convinced me now :-) I will therefore start thinking of a 
patch on the mmc framework instead. I will include you if/when I send 
out the patch to the mmc-list, just for reference if that is ok with you?

Some final thoughts (please comment if you like):
We already have the boot_on constraint, which to me is similar to what a 
new kind of "boot keep state" constraint would be. I think it would be 
no more odd than what boot_on already is. Maybe not a good argument, but 
still..


Kind regards
Ulf Hansson
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