linux-kernel - Re: [PATCH v3 2/4] powerpc/powernv: Enable Offline CPUs to enter deep idle states

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Date:	Mon, 8 Dec 2014 14:33:51 +1100
From:	Paul Mackerras <paulus@...ba.org>
To:	"Shreyas B. Prabhu" <shreyas@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org,
	"Preeti U. Murthy" <preeti@...ux.vnet.ibm.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>, linux-pm@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v3 2/4] powerpc/powernv: Enable Offline CPUs to enter
 deep idle states

On Thu, Dec 04, 2014 at 12:58:21PM +0530, Shreyas B. Prabhu wrote:
> From: "Preeti U. Murthy" <preeti@...ux.vnet.ibm.com>
> 
> The secondary threads should enter deep idle states so as to gain maximum
> powersavings when the entire core is offline. To do so the offline path
> must be made aware of the available deepest idle state. Hence probe the
> device tree for the possible idle states in powernv core code and
> expose the deepest idle state through flags.
> 
> Since the  device tree is probed by the cpuidle driver as well, move
> the parameters required to discover the idle states into an appropriate
> common place to both the driver and the powernv core code.
> 
> Another point is that fastsleep idle state may require workarounds in
> the kernel to function properly. This workaround is introduced in the
> subsequent patches. However neither the cpuidle driver or the hotplug
> path need be bothered about this workaround.
> 
> They will be taken care of by the core powernv code.
> 
> Originally-by: Srivatsa S. Bhat <srivatsa@....edu>
> Signed-off-by: Preeti U. Murthy <preeti@...ux.vnet.ibm.com>
> Signed-off-by: Shreyas B. Prabhu <shreyas@...ux.vnet.ibm.com>

Reviewed-by: Paul Mackerras <paulus@...ba.org>
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