linux-kernel - Re: [RFC] cpuidle - remove the power

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Message-ID: <1720382.g37yj6OOdX@vostro.rjw.lan>
Date:	Mon, 10 Dec 2012 23:41:55 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Julius Werner <jwerner@...omium.org>
Cc:	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Francesco Lavra <francescolavra.fl@...il.com>,
	linux-pm@...r.kernel.org, Kevin Hilman <khilman@...com>,
	Deepthi Dharwar <deepthi@...ux.vnet.ibm.com>,
	Trinabh Gupta <g.trinabh@...il.com>,
	Lists Linaro-dev <linaro-dev@...ts.linaro.org>,
	len.brown@...el.com, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Sameer Nanda <snanda@...omium.org>, Len Brown <lenb@...nel.org>
Subject: Re: [RFC] cpuidle - remove the power_specified field in the driver

On Monday, December 10, 2012 11:09:58 AM Julius Werner wrote:
> Hi,
> 
> What is the current status of this? Daniel, do you think you have got
> enough feedback to submit a definitive patch for this? Rafael, would
> you approve of such a change?

I need to talk to Len about that before I give you a reliable answer.

Thanks,
Rafael


> The bug with dynamically added C-states that is tied to this still
> hurts the battery life for some users across all distros every day, so
> I think it would be valuable to get a consistent solution into the
> mainline soon before everyone has to roll their own.
> 
> On 11/12/2012 09:26 PM, Daniel Lezcano wrote:
> > This patch follows the discussion about reinitializing the power usage
> > when a C-state is added/removed.
> >
> >  https://lkml.org/lkml/2012/10/16/518
> >
> > We realized the power usage field is never filled and when it is
> > filled for tegra, the power_specified flag is not set making all these
> > values to be resetted when the driver is initialized with the set_power_state
> > function.
> >
> > Julius and I feel this is over-engineered and the power_specified
> > flag could be simply removed and continue assuming the states are
> > backward sorted.
> >
> > The menu governor select function is simplified as the power is ordered.
> > Actually the condition is always true with the current code.
> >
> > The cpuidle_play_dead function is also simplified by doing a reverse lookup
> > on the array.
> >
> > The set_power_states function is removed as it does no make sense anymore.
> >
> > Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> > ---
> >  drivers/cpuidle/cpuidle.c        |   17 ++++-------------
> >  drivers/cpuidle/driver.c         |   25 -------------------------
> >  drivers/cpuidle/governors/menu.c |    8 ++------
> >  include/linux/cpuidle.h          |    2 +-
> >  4 files changed, 7 insertions(+), 45 deletions(-)
> >
-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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