Date: Fri, 05 Jun 2009 17:56:56 -0700 (PDT)
Message-Id: <20090605.175656.95336229.davem@davemloft.net>
To: benh@kernel.crashing.org
Cc: subrata@linux.vnet.ibm.com, sachinp@linux.vnet.ibm.com,
       sfr@canb.auug.org.au, greg@kroah.com, linux-kernel@vger.kernel.org,
       Linuxppc-dev@ozlabs.org, linux-next@vger.kernel.org, paulus@samba.org,
       Geert.Uytterhoeven@sonycom.com, geert@linux-m68k.org
Subject: Re: [BUILD FAILURE 01/04] Next June 04:PPC64 randconfig
 [drivers/staging/comedi/drivers.o]
From: David Miller <davem@davemloft.net>
In-Reply-To: <1244244749.31984.16.camel@pasglop>
References: <20090605182625.24093.7808.sendpatchset@elm3a191.beaverton.ibm.com>
	<1244244749.31984.16.camel@pasglop>
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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Sat, 06 Jun 2009 09:32:29 +1000

> 
>> I tried this. But, with some catch. ‘PAGE_KERNEL_NOCACHE’ seems to be the
>> choice for majority of architectures like frv, m32r, sh, x86, etc, as Geert
>> mentions below. However, i believe POWERPC defines it as ‘PAGE_KERNEL_NC‘
>> found at arch/powerpc/include/asm/pte-common.h.
>> 
>> Paul/Banjamin,
>> Can you please confirm this ?
> 
> Read my reply to Greg. Why the heck are you trying to map memory
> non-cacheable in the first place ?

I agree, this is extremely fishy.

I guess the issue is that the driver wants consistent DMA memory
but wants to allocate a huge area vmap() style.
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