linux-kernel - Re: [PATCH] mach-shmobile: Emma Mobile EV2 SMP prototype code

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Date:	Wed, 9 May 2012 23:52:47 +0900
From:	Magnus Damm <magnus.damm@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Marc Zyngier <marc.zyngier@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"horms@...ge.net.au" <horms@...ge.net.au>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"linux-sh@...r.kernel.org" <linux-sh@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"rjw@...k.pl" <rjw@...k.pl>,
	"lethal@...ux-sh.org" <lethal@...ux-sh.org>,
	"olof@...om.net" <olof@...om.net>
Subject: Re: [PATCH] mach-shmobile: Emma Mobile EV2 SMP prototype code

On Wed, May 9, 2012 at 10:45 PM, Arnd Bergmann <arnd@...db.de> wrote:
> On Wednesday 09 May 2012, Marc Zyngier wrote:
>> On 09/05/12 13:12, Arnd Bergmann wrote:
>> > On Wednesday 09 May 2012, Magnus Damm wrote:
>> >>  static unsigned int __init shmobile_smp_get_core_count(void)
>> >>  {
>> >> @@ -31,6 +32,9 @@ static unsigned int __init shmobile_smp_
>> >>    if (is_r8a7779())
>> >>            return r8a7779_get_core_count();
>> >>
>> >> +  if (is_emev2())
>> >> +          return emev2_get_core_count();
>> >> +
>> >>    return 1;
>> >>  }
>> >>
>> >> @@ -41,6 +45,9 @@ static void __init shmobile_smp_prepare_
>> >>
>> >>    if (is_r8a7779())
>> >>            r8a7779_smp_prepare_cpus();
>> >> +
>> >> +  if (is_emev2())
>> >> +          emev2_smp_prepare_cpus();
>> >>  }
>> >>
>> >>  int shmobile_platform_cpu_kill(unsigned int cpu)
>> >> ...
>> >
>> > This shows that we really want an abstraction for soc-specific SMP ops
>> > even within one platform, and we'll need the same thing for multiplatform.
>> >
>> > Marc Zyngier already proposed a solution for this last year, but I
>> > think we couldn't agree on the details back then before he lost interest.
>> > I think we should pick that up again and get it into 3.6 so the code above
>> > can be simplified and we can do the multiplatform solution. We'll probably
>> > discuss the details in Hong Kong in a couple of weeks, so there is no
>> > point in changing it now, but I'd hope that you can migrate this to
>> > whatever we come up with in the following merge window.
>>
>> I'm happy to revive the series if there is an interest.
>
> Ok, good. I think we were almost there the last time, but I don't
> know if Russell still had any objections. Magnus, can you comment on
> the "[PATCH v6 09/15] ARM: SoC: convert shmobile SMP to SoC descriptor"
> patch from February to see if it fits your needs?

I took the liberty to give some comments here instead. I've gone
through the patch and it looks good in general. I have not tested it
but I'd be happy to fix whatever fallout that may happen.

The patch is pretty close to be a perfect fit from my point of view.
This is definitely a step in the right direction. I am however a bit
hesitant with how the CPU hotplug code ended up, but at the same time
I don't really have any better suggestions. I think I simply need to
convert it to be a full per-soc implementation.

Thanks!

/ magnus
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