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Date:   Fri, 04 Dec 2009 10:12:18 -0800
From:   David Daney <ddaney@caviumnetworks.com>
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To:     Ed Okerson <ed.okerson@gmail.com>
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Subject: Re: mmap KSEG1
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Ed Okerson wrote:
> Is it possible to mmap an address in KSEG1 so a user space app can
> read/write to an IO device uncached?
> 

It depends on your definition of 'possible'.  The mips32/64 architecture 
specification has a 'C' field in the EntryLo register that controls 
cachability, so given an appropriate device driver it should be doable.

Calling  __ioremap() with the appropriate flags should allow you to set 
the 'C' bits.

Depending on your requirements, you might be able to get by using 
/dev/mem and some 'sync' instructions, instead of establishing an 
uncached mapping.


David Daney