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

[Maciej Purski]

On 12/15/2017 04:19 PM, Mark Brown wrote:
> On Wed, Dec 13, 2017 at 10:25:00AM +0100, Maciej Purski wrote:
>
> > > 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.
>
> We only really need to lock the supplies when doing the actual mechanics
> of voltage changes so I'm not sure I see a big issue here - if we always
> go through balancing first then voltage setting it should be fine.  If
> everything is always balancing (even uncoupled regulators) then part of
> the transition should be moving some if not all of the data updates to
> balancing.

Now I can understand your point, but I still have doubts what is the advantage 
of that solution. For non-coupled regulators we end up with useless data 
structure - coupling_desc. That also might cause some confusion. We expect 
coupled regulators to be a very rare case, so in most of the cases we will have 
a pointless structure in reg_dev with a pointer to itself. Maybe you suggest 
that coupling_desc should contain something different?