Re: [RFC PATCH 1/2] regulator: core: Add regulator_set_voltage_min()

[Taras Kondratiuk]

On 04/23/2013 04:45 PM, Mark Brown wrote:
> On Tue, Apr 23, 2013 at 02:44:58PM +0300, Taras Kondratiuk wrote:
>
> > GPU voltage is regulated by some devfreq driver.
> > CPU voltage is regulated by generic cpufreq-cpu0 driver.
> > Both drivers know only about their operational points.
> > They don't know anything about chip limits.
> Clearly at least the lower bound is known to the drivers...
Do you mean a voltage of the lowest operation point?

> > I see two options here:
> > 1. Pass somehow chip limits to drivers so they can limit their request.
> >     Pros: No need for regulator_set_voltage_min()
> >     Cons: a) Need to pass info about chip limits to driver. New API?
> Why on earth would this need a new API?
I think I'm missing something.
How can I pass chip limits to a driver in some generic way?
> >           b) CPU and GPU may have different limits,
> >              so after very first request voltage may violate
> >              CPU or GPU range.
> If the CPU and GPU drivers are trying to select incompatible
> configurations then we really ought to be detecting that, ignoring it
> seems like an obvious failure.  There's a bootstrapping problem but
> that's also an issue with specifying only the minimum voltage...
>
> > 2. Define chip limits in Reg X constraints.
> >     Pros: Limits will be applied to driver's request transparently.
> >           No need to pass info about limits to driver.
> >           Limits are set before the first request, so no violation.
> >     Cons: regulator_set_voltage_min() is needed.
> > IMHO option #2 is better.
> > Do you see other ways?
> Above you clearly say that this is all modelling operating points.  If
> you're doing that then I would expect the drivers to be talking
> operating points to an operating point abstraction.
I went through several SoC datasheets and found that min approach
won't work for some of them (like AM335x).
The only safe way is to send max OPP voltage as a max_uV.
So please skip this series.

--
BR
Taras Kondratiuk | GlobalLogic

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