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

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Date:	Sat, 2 Jun 2012 18:23:40 +0200
From:	Sam Ravnborg <sam@...nborg.org>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
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

> 
> As I mentioned in my other mail, I am thinking of changing them to
> arch_cpu_pre_starting(), arch_cpu_pre_online() and arch_cpu_post_online().
> Let me know what you think of those names.
Much better than "__" - so if none of the guys that excel in core
code objects go for that.

> Would you kindly add a changelog and your sign-off to this patch?
Will do in next revision.

...

Thanks for the throughfull review.
I will address all points - including passing the pointer down,
as I assume you have some future plans with that pointer.

> 
> I still didn't get how this solves the original problem of
> not having sparc_cpu_model set to sparc_leon. You mentioned
> that by the time we reach leon_smp_cpu_startup, that variable
> is not set. Even inside leon_smp_cpu_startup, I don't immediately
> see where it is set. Am I missing something?

After looking more closely at the code it is my understanding
that a leon CPU when started will actually jump to the reset
vector and start from there.
So the secondary CPU's will run long time after
sparc_cpu_model is set so we can safely use it.

The sun based cpu will in comparsion jump to
an address supplied to a prom call - so they do not
jump to the reset vector.
But they also have sparc_cpu_model set so no problem there
either.

All this are my deductions from reading the code - but this
is not an area I have looked at otherwise..

I may not find time today to cook up a new version of
the patch - but then you will have it tomorrow.

	Sam
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