linux-kernel - Re: [v6 PATCH 0/7]: cpuidle/x86/POWER: Cleanup idle power management code in x86, cleanup drivers/cpuidle/cpuidle.c and introduce cpuidle to POWER.

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Message-ID: <20090924051238.GA5963@linux.vnet.ibm.com>
Date:	Thu, 24 Sep 2009 10:42:41 +0530
From:	Arun R Bharadwaj <arun@...ux.vnet.ibm.com>
To:	Len Brown <lenb@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Joel Schopp <jschopp@...tin.ibm.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>, Ingo Molnar <mingo@...e.hu>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Dipankar Sarma <dipankar@...ibm.com>,
	Balbir Singh <balbir@...ibm.com>,
	Gautham R Shenoy <ego@...ibm.com>,
	Shaohua Li <shaohua.li@...el.com>,
	Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>,
	Arun Bharadwaj <arun@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-acpi@...r.kernel.org
Subject: Re: [v6 PATCH 0/7]: cpuidle/x86/POWER: Cleanup idle power
	management code in x86, cleanup drivers/cpuidle/cpuidle.c and
	introduce cpuidle to POWER.

* Arun R Bharadwaj <arun@...ux.vnet.ibm.com> [2009-09-22 16:55:27]:

Hi Len, (or other acpi folks),

I had a question regarding ACPI-cpuidle interaction in the current
implementation.

Currently, every cpu (i.e. acpi_processor) registers to cpuidle as
a cpuidle_device. So every cpu has to go through the process of
setting up the idle states and then registering as a cpuidle device.

What exactly is the reason behind this?

Is this really necessary or can we have a system-wide one-time registering
to cpuidle by ACPI?

I'm currently in the process of enabling cpuidle for POWER systems and
find that having a system-wide registering mechanism to be a cleaner
design.

--arun
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