RE: [patch 09/11] PAT x86: Add ioremap_wc support

[Pallipadi, Venkatesh]

>-----Original Message-----
>From: Andi Kleen [mailto:andi@xxxxxxxxxxxxxx] 
>Sent: Thursday, January 10, 2008 11:09 AM
>To: Pallipadi, Venkatesh
>Cc: ebiederm@xxxxxxxxxxxx; rdreier@xxxxxxxxx; 
>torvalds@xxxxxxxxxxxxxxxxxxxx; gregkh@xxxxxxx; 
>airlied@xxxxxxxxx; davej@xxxxxxxxxx; mingo@xxxxxxx; 
>tglx@xxxxxxxxxxxxx; hpa@xxxxxxxx; 
>linux-kernel@xxxxxxxxxxxxxxx; Siddha, Suresh B
>Subject: Re: [patch 09/11] PAT x86: Add ioremap_wc support
>
>venkatesh.pallipadi@xxxxxxxxx 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@xxxxxxxxx] 
>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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/