linux-kernel - Re: [PATCH 1/2] Samsung SoC ADC: use regulator (VDD for ADC).

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Message-ID: <20110620101737.GA31864@opensource.wolfsonmicro.com>
Date:	Mon, 20 Jun 2011 11:17:38 +0100
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	myungjoo.ham@...il.com
Cc:	linux-arm-kernel@...ts.infradead.org,
	Kukjin Kim <kgene.kim@...sung.com>,
	Russell King <linux@....linux.org.uk>,
	linux-kernel@...r.kernel.org, dg77.kim@...sung.com,
	kyungmin.park@...sung.com, Ben Dooks <ben-linux@...ff.org>
Subject: Re: [PATCH 1/2] Samsung SoC ADC: use regulator (VDD for ADC).

On Mon, Jun 20, 2011 at 02:16:59PM +0900, MyungJoo Ham wrote:
> On Sun, Jun 19, 2011 at 12:06 AM, Mark Brown
> > On Thu, Jun 16, 2011 at 05:30:02PM +0900, MyungJoo Ham wrote:

> >> +     adc->vdd = regulator_get(dev, S3C_ADC_REGULATOR_NAME);

> > I'm not convinced that the #define for the name is terribly good style
> > here, especially given that you actually call it vdd in the code.

> Then, would it be fine to use as [ regulator_get(dev, "vdd"); ] ?

Yes.

> >> +     if (IS_ERR_OR_NULL(adc->vdd)) {
> >> +             dev_dbg(dev, "operating without regulator %s.\n", S3C_ADC_REGULATOR_NAME);
> >> +             adc->vdd = NULL; /* Do not control regulator */
> >> +     }
> >> +

> > No, don't do this.  Just unconditionally assume the regulator is present
> > if power is essential for use of the device.  The regulator API will
> > stub out correctly if it's not in use to allow things to proceed and if
> > vdd is genuinely not hooked up then the driver can't function.

> This ADC driver is for every ADC from S3C24xx series to Exynos4 (and
> its successors as well).
> The regulator (VDD for ADC) is essential for the recent chips
> (S5PC110, S5PV210, and Exynos4).
> I was just worried about the old boards using the same ADC driver
> (mach-s3c2410/mach-*.c, mach-s3c6410/mach-*.c, and so on) without
> ADC-VDD regulators defined.

If the regulator API is in use on a system it is reasonable to expect it
to be set up correctly for the system.

> However, no s3c compliance defconfigs have ever used CONFIG_REGULATOR.
> Thus, it seems that it's safe to enforce using "vdd" with regulators
> in plat-samsung's ADC driver.
> I'll proceed as you have commented.

Note that SMDK6410 and Cragganmore are both using regulators fairly
extensively.
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