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Message-ID: <924EFEDD5F540B4284297C4DC59F3DEE5A281A@orsmsx423.amr.corp.intel.com>
Date: Thu, 10 Jan 2008 11:25:25 -0800
From: "Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>
To: "Andi Kleen" <andi@...stfloor.org>
Cc: <ebiederm@...ssion.com>, <rdreier@...co.com>,
<torvalds@...ux-foundation.org>, <gregkh@...e.de>,
<airlied@...net.ie>, <davej@...hat.com>, <mingo@...e.hu>,
<tglx@...utronix.de>, <hpa@...or.co>,
<linux-kernel@...r.kernel.org>,
"Siddha, Suresh B" <suresh.b.siddha@...el.com>
Subject: RE: [patch 09/11] PAT x86: Add ioremap_wc support
>-----Original Message-----
>From: Andi Kleen [mailto:andi@...stfloor.org]
>Sent: Thursday, January 10, 2008 11:09 AM
>To: Pallipadi, Venkatesh
>Cc: ebiederm@...ssion.com; rdreier@...co.com;
>torvalds@...ux-foundation.org; gregkh@...e.de;
>airlied@...net.ie; davej@...hat.com; mingo@...e.hu;
>tglx@...utronix.de; hpa@...or.co;
>linux-kernel@...r.kernel.org; Siddha, Suresh B
>Subject: Re: [patch 09/11] PAT x86: Add ioremap_wc support
>
>venkatesh.pallipadi@...el.com writes:
>> Index: linux-2.6.git/include/asm-generic/iomap.h
>> ===================================================================
>> --- linux-2.6.git.orig/include/asm-generic/iomap.h
>2008-01-08 03:31:37.000000000 -0800
>> +++ linux-2.6.git/include/asm-generic/iomap.h
>2008-01-08 05:15:56.000000000 -0800
>> @@ -65,4 +65,8 @@
>> extern void __iomem *pci_iomap(struct pci_dev *dev, int
>bar, unsigned long max);
>> extern void pci_iounmap(struct pci_dev *dev, void __iomem *);
>>
>> +#ifndef ioremap_wc
>> +#define ioremap_wc ioremap_nocache
>> +#endif
>
>I don't think that's a good idea. Drivers should be able to
>detect this somehow.
>Handling UC mappings as WC will probably give very poor results.
>
It is the other way. ioremap_wc aliases to ioremap_nocache.
This was based on earlier feedback from Roland.
>From: Roland Dreier [mailto:rdreier@...co.com]
>I think ioremap_wc() needs to be available on all archs for this to be
>really useful to drivers. It can be a fallback to ioremap_nocache()
>everywhere except 64-bit x86, but it's not nice for every driver that
>wants to use this to need an "#ifdef X86" or whatever.
Thanks,
Venki
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