linux-kernel - Re: [PATCH] leds: lm3530: fix handling of already enabled regulators

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Message-ID: <CAF+7xWkzy5e0rcpwprEE3VWTikOu2+qtsgfdhTN12-yonDxadA@mail.gmail.com>
Date:	Tue, 24 Apr 2012 10:09:00 +0800
From:	Axel Lin <axel.lin@...il.com>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Cc:	linux-kernel@...r.kernel.org,
	Shreshtha Kumar Sahu <shreshthakumar.sahu@...ricsson.com>,
	"Milo(Woogyom) Kim" <milo.kim@...com>,
	Richard Purdie <rpurdie@...ys.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Liam Girdwood <lrg@...com>
Subject: Re: [PATCH] leds: lm3530: fix handling of already enabled regulators

2012/4/23 Mark Brown <broonie@...nsource.wolfsonmicro.com>:
> On Sun, Apr 22, 2012 at 11:11:48PM +0800, Axel Lin wrote:
>
>>               drvdata->regulator = NULL;
>>               goto err_regulator_get;
>>       }
>> +     drvdata->enable = regulator_is_enabled(drvdata->regulator);
>>
>
> This isn't sufficient for what the driver is doing - it also needs to
> enable the regulator.  Regulator enables are reference counted (since
> the regulator can be shared by many device supplies) so if this driver
> doesn't reference the regulator when it's needed then it could get
> powered off.

The regulator_enable() is called in lm3530_init_registers().

>
> If this regulator is the actual LED then the current default of assuming
> the regulator is off on boot isn't ideal either as it means that if the
> regulator is enabled on boot then the LED may be left on even though the
> driver thinks it's off.

Hi Shreshtha,
I think without this patch you can see the symptom Mark mentioned if the
regulator is enabled on boot.
Any chance to test if this patch works or not?

Regards,
Axel
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