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

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Date:	Fri, 13 Jun 2014 17:24:20 +0530
From:	Chander Kashyap <k.chander@...sung.com>
To:	Kukjin Kim <kgene.kim@...sung.com>
Cc:	Doug Anderson <dianders@...omium.org>,
	Chander Kashyap <k.chander@...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 Wed, Jun 11, 2014 at 8:58 PM, Kukjin Kim <kgene.kim@...sung.com> wrote:
> 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?
>>

This patch is effectively changing the mcpm_entry_point address from
nsbase + 0x1c to nsbase + 0x8

Hence while integrating with mainline u-boot we need to take care for
new mcpm_entry_point address.

With Chromebook it works straightforward.


> Sure, I will ;-)
>
> Thanks,
> Kukjin
>
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