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

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Date:	Thu, 12 Jun 2014 00:28:15 +0900
From:	Kukjin Kim <kgene.kim@...sung.com>
To:	Doug Anderson <dianders@...omium.org>
CC:	Chander Kashyap <k.chander@...sung.com>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	Kevin Hilman <khilman@...aro.org>,
	Andrew Bresticker <abrestic@...omium.org>,
	Inderpal Singh <inderpal.s@...sung.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Chander Kashyap <chander.kashyap@...aro.org>,
	"olof@...om.net" <olof@...om.net>,
	Tushar Behera <trblinux@...il.com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Thomas Abraham <thomas.ab@...sung.com>,
	Abhilash Kesavan <a.kesavan@...sung.com>,
	Javier Martinez Canillas <javier.martinez@...labora.co.uk>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>
Subject: Re: [PATCH] ARM: EXYNOS: mcpm: Don't rely on firmware's secondary_cpu_start

On 06/12/14 00:19, Doug Anderson wrote:
> Chander,
>
> On Tue, Jun 10, 2014 at 9:52 PM, Chander Kashyap<k.chander@...sung.com>  wrote:
>> Hi Doug,
>>
>> On Tue, Jun 10, 2014 at 9:19 PM, Nicolas Pitre<nicolas.pitre@...aro.org>  wrote:
>>> 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).
>>>>
>>
>> No Its not plain WFI.
>>
>> All cores in Exynos5420 can be powered off independently.
>> This functionality has been tested.
>>
>> Below is the link for the posted patches.
>>
>> https://lkml.org/lkml/2014/6/10/194
>>
>> And as Nicolas wrote, these patches need MCPM for that.
>
> Most excellent!  I should have been more clear that I only knew about
> how CPUidle worked in our local production kernel.  There I'm pretty
> sure CPUidle is just WFI/WFE.  If you've got patches to do better then
> that's great!
>
> ...can you confirm that my patch doesn't interfere with your improved
> CPUidle?  It's been Acked by Nicolas (thanks!) so I'd imagine it will
> land shortly.  Kukjin: I assume you'll be taking this?
>
Sure, I will ;-)

Thanks,
Kukjin
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