[RFC V2] OPP: Redefine bindings to overcome shortcomings
broonie at kernel.org
Fri Jan 23 03:52:06 PST 2015
On Fri, Jan 23, 2015 at 12:39:14PM +0100, Lucas Stach wrote:
> > + Required properties:
> > + - opp-khz: Frequency in kHz
> > + - opp-microvolt: voltage in micro Volts
> Each OPP voltage should be defined by the triplet of minimum,
> nominal/typical, maximum. This lets you specify exact tolerances in each
> direction and should cover most use-cases.
> IMHO it would make sense to just define opp-microvolt as an array of
> those 3 values, so the DT doesn't get bloated with a lot more
> A typical value for a CPU could then look like this:
> opp-microvolt = <800000 850000 1100000>
I tend to agree that this is clearer. It might be nice to have variants
for specifying directly as a percentage but I don't think it's really
worth the complexity.
> For devices without any tolerance you can just specify the same value
> three times and be done with it:
> opp-microvolt = <900000 900000 900000>
If we change the binding to be typ/min/max rather than min/typ/max then
we could also do this by allowing either one or three values to be
specified. That might be more worth the complexity especially given...
> > + Optional properties:
> > + - turbo-mode: Marks the volt-freq pair as turbo pair.
> > + - status: Marks the node enabled/disabled.
> > + - voltage-tolerance: Specify the CPU voltage tolerance in percentage.
> Please let's drop this.
DT bindings are supposed to be stable, this means the code should accept
old bindings and they should be documented as deprecated.
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