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Re: address translation with TLB

To: Ralf Baechle <ralf@oss.sgi.com>
Subject: Re: address translation with TLB
From: Tom Appermont <tea@sonycom.com>
Date: Thu, 19 Apr 2001 10:01:47 +0200
Cc: linux-mips@oss.sgi.com
In-reply-to: <20010417141122.D7177@bacchus.dhis.org>; from ralf@oss.sgi.com on Tue, Apr 17, 2001 at 02:11:22PM -0300
References: <20010414102901.A13595@ginger.sonytel.be> <20010417141122.D7177@bacchus.dhis.org>
Sender: owner-linux-mips@oss.sgi.com
On Tue, Apr 17, 2001 at 02:11:22PM -0300, Ralf Baechle wrote:
> 
> Sane designs make sure that peripherals are at physical addresses of 512mb
> or less so can be addressed through KSEG1 without using TLB entries.  So
> far the only violation of this rule are the Jazz systems.
> 

In the setup.c file for the jazz board, is written:

        add_wired_entry (0x02000017, 0x03c00017, 0xe0000000, PM_64K);
        add_wired_entry (0x02400017, 0x02440017, 0xe2000000, PM_16M);
        add_wired_entry (0x01800017, 0x01000017, 0xe4000000, PM_4M);


Why do these physical addresses which are all below 512MB need TLB entries? 


Greetz,

Tom


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