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Date: Thu, 19 May 2011 22:02:33 -0500
From: Kazutomo Yoshii <kazutomo@mcs.anl.gov>
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To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [bg-linux] [PATCH 5/7] [RFC] force 32-byte aligned kmallocs
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On 05/19/2011 09:13 PM, Benjamin Herrenschmidt wrote:
> On Fri, 2011-05-20 at 12:08 +1000, Benjamin Herrenschmidt wrote:
>    
>> On Thu, 2011-05-19 at 20:32 -0500, Kazutomo Yoshii wrote:
>>      
>>> Actually DMA sends invalidate requests to the snoop unit(L2 level).
>>> BGP SoC is a bit different from other 4xx base.
>>>        
>> Well, some other 44x also have a snooping L2 (more or less), but L1 is
>> usually the problem.
>>      
> Hrm... looking at the doco you pointed me to, it looks like the L1 -is-
> coherent, it gets snoop kills from the L2.
>    
Right, L1D is coherent if write throug is set.
L1I(virtually tagged) is not coherent, btw.

> Ok so we do need to make this non-coherent cache stuff a runtime option
> (well, we need that for 440+476 too anyways so may as well do it now).
>    
What sort of runtime option do you mean?

- kaz
> As for the alignment of kmalloc, it looks like a hack that should be
> done in the torus code itself.
>
> Cheers,
> Ben.
>
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