linux-kernel - Re: [PATCH] ARM: EXYNOS: mcpm: Don't rely on firmware's secondary_cpu

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Message-ID: <alpine.LFD.2.11.1406101146140.25775@knanqh.ubzr>
Date:	Tue, 10 Jun 2014 11:49:27 -0400 (EDT)
From:	Nicolas Pitre <nicolas.pitre@...aro.org>
To:	Doug Anderson <dianders@...omium.org>
cc:	Chander Kashyap <chander.kashyap@...aro.org>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Abhilash Kesavan <a.kesavan@...sung.com>,
	Andrew Bresticker <abrestic@...omium.org>,
	Inderpal Singh <inderpal.s@...sung.com>,
	Thomas Abraham <thomas.ab@...sung.com>,
	"olof@...om.net" <olof@...om.net>,
	Tushar Behera <trblinux@...il.com>,
	Kevin Hilman <khilman@...aro.org>,
	Javier Martinez Canillas <javier.martinez@...labora.co.uk>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARM: EXYNOS: mcpm: Don't rely on firmware's
 secondary_cpu_start

On Tue, 10 Jun 2014, Doug Anderson wrote:

> My S-state knowledge is not strong, but I believe that Lorenzo's
> questions matter if we're using S2 for CPUidle (where we actually turn
> off power and hot unplug CPUs) but not when we're using S1 for CPUidle
> (where we just enter WFI/WFE).
> 
> I believe that in ChromeOS we use S1 CPUidle and that it works fine.
> We've never implemented S2 that I'm aware of.

You'll have to rely on MCPM for that.  That's probably why it hasn't 
been implemented before.


Nicolas
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