Re: [PATCH v3 4/4] regulator: core: Balance coupled regulators voltages

[Maciej Purski]

On 12/12/2017 12:54 PM, Mark Brown wrote:
> On Thu, Dec 07, 2017 at 10:46:15AM +0100, Maciej Purski wrote:
>
> > @@ -2447,10 +2482,9 @@ static int _regulator_is_enabled(struct regulator_dev *rdev)
> >   	return rdev->desc->ops->is_enabled(rdev);
> >   }
> >   
> > -static int _regulator_list_voltage(struct regulator *regulator,
> > -				    unsigned selector, int lock)
> > +static int _regulator_list_voltage(struct regulator_dev *rdev,
> > +				   unsigned selector, int lock)
> >   {
>
> Please split this refactoring of _list_voltage() into a separate patch
> for ease of review.  It can go in separately which will make this change
> smaller and easier to review.
>
> > @@ -2928,6 +2961,35 @@ static int regulator_set_voltage_unlocked(struct regulator *regulator,
> >   	if (ret < 0)
> >   		goto out2;
> >   
> > +	/*
> > +	 * If the regulator is not coupled just set voltage normally, else
> > +	 * return after changing consumer demands without changing voltage.
> > +	 * This will be handled outside the function
> > +	 * by regulator_balance_coupled()
> > +	 */
> > +	if (!rdev->coupling_desc) {
> > +		ret = regulator_set_voltage_rdev(regulator->rdev,
> > +						 min_uV, max_uV);
> > +		if (ret < 0)
> > +			goto out2;
> > +	}
>
> As I think I said on the previous version I'm not enthusiastic about
> having two separate code paths for setting the voltage, it makes it much
> more likely that things will break especially given how rare coupled
> regulators are.  It would be cleaner to make uncoupled regulators just
> be a special case of coupled regulators, that way more of the code is
> shared.  To that end I'd adjust the code so that we always have a
> coupling descriptor and then handle the case where there's only one
> regulator described in there.

Do you have any suggestion, how should I implement that path? The thing which
makes it more complicated is locking, because set_voltage_unlocked is done under 
one regulator's mutex and its suppliers, while balance procedure locks every 
coupled regulator without its suppliers. The suppliers for a single regulator 
are locked when setting a single regulator's voltage takes place.