Re: [Ksummit-discuss] [TECH(CORE?) TOPIC] Energy conservation bias interfaces

[Mark Brown <broonie@kernel.org>]

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On Mon, May 12, 2014 at 05:23:11PM +0530, Amit Kucheria wrote:
> On Tue, May 6, 2014 at 6:24 PM, Rafael J. Wysocki <rjw@rjwysocki.net> wrote:

> > First of all, it would be good to have a place where subsystems and device
> > drivers can go and check what the current "energy conservation bias" is in
> > case they need to make a decision between delivering more performance and
> > using less energy.  Second, it would be good to provide user space with

> Drivers are always designed to go as fast as possible until there is
> nothing to do and runtime PM kicks in. Do we really want drivers that
> slow down file copy to the USB stick because we are on battery? Or
> degrade audio/video quality to save power? The only usecase I can come
> up with where this makes sense is the wifi connection where the driver
> should perhaps throttle bitrates if the network isn't being used
> actively. But that is a driver-internal decision.

There's some tradeoffs around audio as well actually - typically there
is a lot of room for degrading performance without much impact on real
world users.  That said of course hardware manufacturers are constantly
working to eliminate the need for such tradeoffs so the longer we leave
this stuff the less relevant it becomes.  I'd guess this is fairly
common for analogue circuits, a similar thing used to be the case with
PMICs though for modern devices the need for explict tuning has been
mostly eliminated and the hardware can do it autonomously (at least for
the bits that burn most power).

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