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RE: mmap'ed memory cacheable or uncheable

To: "Jun Sun" <jsun@mvista.com>, "Teresa Tao" <Teresat@tridentmicro.com>
Subject: RE: mmap'ed memory cacheable or uncheable
From: "Teresa Tao" <Teresat@tridentmicro.com>
Date: Fri, 25 Jul 2003 15:52:33 -0700
Cc: <linux-mips@linux-mips.org>
Original-recipient: rfc822;linux-mips@linux-mips.org
Sender: linux-mips-bounce@linux-mips.org
Thread-index: AcNS+GFAtXxthcdyRB2ywR1T0NJ4DAABsVlA
Thread-topic: mmap'ed memory cacheable or uncheable
How about if I specify the following flags in my mmap routine just like what 
the pgprot_noncached micro did.
        pgprot_val(vma->vm_page_prot) &= ~_CACHE_MASK;
        pgprot_val(vma->vm_page_prot) |= _CACHE_UNCACHED;

Will this have kernel make the mmap'd memory non-cacheable? Or is there a mmap 
non-cacheable patch?

Thanks in advance!

Teresa



-----Original Message-----
From: Jun Sun [mailto:jsun@mvista.com]
Sent: Friday, July 25, 2003 3:02 PM
To: Teresa Tao
Cc: linux-mips@linux-mips.org; jsun@mvista.com
Subject: Re: mmap'ed memory cacheable or uncheable


On Thu, Jul 24, 2003 at 08:26:59PM -0700, Teresa Tao wrote:
> Hi there,
> 
> I got a question regarding the mmap'ed memory. Is the mmap'ed memory 
> cacheable or uncheable? My driver just use the remap_page_range to map a 
> reserved physical memory.
>

I am pretty much sure it is cached, although I can't pin down exactly
where in the mm subsystem it does so - I have had cache bugs related
to mmap().

Jun

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