linux-mips
[Top] [All Lists]

Re: mmap KSEG1

To: Ed Okerson <ed.okerson@gmail.com>
Subject: Re: mmap KSEG1
From: David Daney <ddaney@caviumnetworks.com>
Date: Fri, 04 Dec 2009 10:12:18 -0800
Cc: linux-mips@linux-mips.org
In-reply-to: <83f0348b0912040952h40d4d151n79ca5fc33a830ee2@mail.gmail.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <83f0348b0912040952h40d4d151n79ca5fc33a830ee2@mail.gmail.com>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Thunderbird 2.0.0.21 (X11/20090320)
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

<Prev in Thread] Current Thread [Next in Thread>