linux-kernel - Re: [PATCH] regulator: arizona-ldo1: Only enable status change if we have LDOENA

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Message-ID: <571A536A.9000509@opensource.wolfsonmicro.com>
Date:	Fri, 22 Apr 2016 17:38:02 +0100
From:	Richard Fitzgerald <rf@...nsource.wolfsonmicro.com>
To:	Mark Brown <broonie@...nel.org>
CC:	<lgirdwood@...il.com>, <patches@...nsource.wolfsonmicro.com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] regulator: arizona-ldo1: Only enable status change if
 we have LDOENA

On 22/04/16 16:04, Mark Brown wrote:
> On Fri, Apr 22, 2016 at 02:43:28PM +0100, Richard Fitzgerald wrote:
>> The driver was hardcoding REGULATOR_CHANGE_STATUS on the regulator
>> which made the regulator core assume that it can be powered off.
>>
>> The power state of the regulator is controlled by the LDOENA pin so
>> this patch changes to only setting the REGULATOR_CHANGE_STATUS flag
>> if we have a valid gpio for LDOENA.
> What's the difference between this and the previous version of the patch
> and what problem is this aiming to solve?  If we want to disable the
> regulator why would we not be happy to do that by removing the supply?
The background to all this is that runtime suspend and resume needs to 
know whether the DCVDD turned off. If it definitely turned off a regmap 
cache sync is safe - if not or I can't be sure then I need the overhead 
of a forced reset to restore register defaults before the sync.

What I'm trying to achieve here is to stop the regulator core sending 
false notifications that LDO1 has been turned off. The way that the 
regulator core code handles the disable notifier has no dependency on 
what happens to the parent supply. The REGULATOR_CHANGE_STATUS flag is 
used to indicate whether the status of _this_ regulator can be changed 
(it doesn't affect whether the parent is disabled).

So if LDO1 is disabled without an LDOENA and without this patch, it 
looks like the current core behaviour of the functions 
regulator_disable(), _regulator_disable() and _regulator_do_disable() is:

1) Are we the last user? - Yes
2) _regulator_can_change_status()? - Yes because REGULATOR_CHANGE_STATUS 
is set
3) Send PRE_DISABLE notification
4) call _regulator_do_disable(), no GPIO pin and no disable callback so 
return 0 (claims success even though there was no way to disable it)
5) Send REGULATOR_EVENT_DISABLE
6) Return to regulator_disable() and then disable the parent supply

The result will be that we got a disable notification though LDO1 wasn't 
disabled.

I think it's a bug that LDO1 claimed to be able to turn off when it 
couldn't, and fixing that prevents bogus disable notifications.