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Re: mmap KSEG1

To: Ed Okerson <>
Subject: Re: mmap KSEG1
From: David Daney <>
Date: Fri, 04 Dec 2009 10:12:18 -0800
In-reply-to: <>
Original-recipient: rfc822;
References: <>
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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

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