linux-kernel - Re: [UPDATED PATCH 21/27] sparc32, smpboot: Use generic SMP booting infrastructure

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Date:	Sat, 02 Jun 2012 13:44:29 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	Sam Ravnborg <sam@...nborg.org>
CC:	David Miller <davem@...emloft.net>, tglx@...utronix.de,
	peterz@...radead.org, paulmck@...ux.vnet.ibm.com,
	rusty@...tcorp.com.au, mingo@...nel.org, yong.zhang0@...il.com,
	akpm@...ux-foundation.org, vatsa@...ux.vnet.ibm.com, rjw@...k.pl,
	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	nikunj@...ux.vnet.ibm.com, vapier@...too.org, konrad@...sler.com,
	tkhai@...dex.ru, sparclinux@...r.kernel.org
Subject: Re: [UPDATED PATCH 21/27] sparc32, smpboot: Use generic SMP	booting
 infrastructure

On 06/02/2012 01:31 PM, Srivatsa S. Bhat wrote:

> On 06/02/2012 01:14 PM, Sam Ravnborg wrote:
> 
>> On Sat, Jun 02, 2012 at 08:52:49AM +0200, Sam Ravnborg wrote:
>>> Hi Srivatsa.
>>>
>>> I cannot see how this would work for sparc32...
>>> [Did not notice before...]
>>>
>>>> --- a/arch/sparc/kernel/leon_smp.c
>>>> +++ b/arch/sparc/kernel/leon_smp.c
>>>
>>>> +void __cpuinit __cpu_pre_starting(void *unused)
>>>> +{
>>>> +	unsigned int cpuid = hard_smp_processor_id();
>>>>  
>>>> diff --git a/arch/sparc/kernel/sun4d_smp.c b/arch/sparc/kernel/sun4d_smp.c
>>>> index ddaea31..cd5367a 100644
>>>> --- a/arch/sparc/kernel/sun4d_smp.c
>>>> +++ b/arch/sparc/kernel/sun4d_smp.c
>>>
>>>> +void __cpuinit __cpu_pre_starting(void *unused)
>>>> +{
>>>> +	unsigned int cpuid = hard_smp_processor_id();
>>>>  
>>>> diff --git a/arch/sparc/kernel/sun4m_smp.c b/arch/sparc/kernel/sun4m_smp.c
>>>> index 128af73..ed05f54 100644
>>>> --- a/arch/sparc/kernel/sun4m_smp.c
>>>> +++ b/arch/sparc/kernel/sun4m_smp.c
>>>
>>>> +void __cpuinit __cpu_pre_starting(void *unused)
>>>> +{
>>>> +	unsigned int cpuid = hard_smp_processor_id();
>>>
>>> See how you define a function with the same name three times.
>>> On sparc32 we include all of the above files in the kernel,
>>> and uses various tricks to determine at run-time
>>> which variant to use.
>>>
>>> We need to define these general functions in smp_32.c and
>>> then take relevant action depending on sparc_cpu_model.
>>
>> I took a short look at this.
>> And it is a bit complicated :-(
>>
>> leon is the odd-one here. For reasons I do not understand
>> we have a call from head_32.S to leon_smp_cpu_startup:
>> in trampoline_32.S.
>>
>> But sun4m and sun4d uses the normal path via start_kernel() etc.
>>
>> This has the side-effect that sparc_cpu_model is not set
>> when we call leon_smp_cpu_startup.
>>
> 
> Yes, I saw that too now..
> 


But I'm wondering where will it set sparc_cpu_model to sparc_leon
then.. The only place i saw was setup_arch(), which gets called from
start_kernel(). But if leon doesn't even call start_kernel(), then....?
 
Regards,
Srivatsa S. Bhat

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