linux-kernel - Re: [PATCH 1/2] regulator: anatop: Add power gating support to digital LDOs

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Message-ID: <1392038875.6687.17.camel@pizza.hi.pengutronix.de>
Date:	Mon, 10 Feb 2014 14:27:55 +0100
From:	Philipp Zabel <p.zabel@...gutronix.de>
To:	Mark Brown <broonie@...nel.org>
Cc:	linux-kernel@...r.kernel.org, Liam Girdwood <lgirdwood@...il.com>,
	Shawn Guo <shawn.guo@...aro.org>,
	Anson Huang <b20788@...escale.com>, kernel@...gutronix.de
Subject: Re: [PATCH 1/2] regulator: anatop: Add power gating support to
 digital LDOs

Hi Mark,

Am Montag, den 10.02.2014, 13:15 +0000 schrieb Mark Brown:
> On Thu, Feb 06, 2014 at 03:43:32PM +0100, Philipp Zabel wrote:
> > The ARM, PU, and SOC LDOs in the i.MX6 PMU can completely gate
> > their power output. Since power gating is configured by writing
> > zero to the voltage target bitfield,, store a copy of the
> > voltage selector to be restored when reenabling the regulator.
> 
> This is mostly good but...
>
> >  static int anatop_regmap_set_voltage_sel(struct regulator_dev *reg,
> >  					unsigned selector)
> >  {
> >  	struct anatop_regulator *anatop_reg = rdev_get_drvdata(reg);
> > +	int ret;
> >  
> >  	if (!anatop_reg->control_reg)
> >  		return -ENOTSUPP;
> >  
> > -	return regulator_set_voltage_sel_regmap(reg, selector);
> > +	ret = regulator_set_voltage_sel_regmap(reg, selector);
> > +	if (!ret)
> > +		anatop_reg->sel = selector;
> > +	return ret;
> >  }
> 
> ...I don't understand this.  If the regulator is disabled won't this
> cause it to be reenabled since we just write the stored selector in to
> do that?  What I'd expect to see happening is the data being written to
> the cache always and only written to the hardware if it's enabled.

yes, thanks. I'll fix this. What should happen if the
regulator_set_voltage_sel_regmap fails? Is it ok to still
set the cache in this case?

> > +static int anatop_regmap_disable(struct regulator_dev *reg)
> > +{
> > +	struct anatop_regulator *anatop_reg = rdev_get_drvdata(reg);
> > +
> > +	if (!anatop_is_core_reg(anatop_reg))
> > +		return -ENOTSUPP;
> > +
> > +	return regulator_set_voltage_sel_regmap(reg, LDO_POWER_GATE);
> > +}
> 
> It's starting to seem like it's worth having separate ops for the core
> regulator rather than all these conditionals.

Will do.

regards
Philipp

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