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Re: early_ioremap for MIPS

To: "M. Warner Losh" <imp@bsdimp.com>
Subject: Re: early_ioremap for MIPS
From: "Maciej W. Rozycki" <macro@linux-mips.org>
Date: Mon, 11 Feb 2008 10:27:41 +0000 (GMT)
Cc: florian.fainelli@telecomint.eu, linux-mips@linux-mips.org
In-reply-to: <20080210.154401.1655407815.imp@bsdimp.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <200802071932.23965.florian.fainelli@telecomint.eu> <Pine.LNX.4.64N.0802081058350.7017@blysk.ds.pg.gda.pl> <20080210.154401.1655407815.imp@bsdimp.com>
Sender: linux-mips-bounce@linux-mips.org
On Sun, 10 Feb 2008, M. Warner Losh wrote:

> :  There is hardly any need as generally KSEG0/KSEG1 and XPHYS mappings 
> : fulfil the need and are always available, even before paging has been 
> : initialised.  Some 32-bit systems with devices outside low 512MB of 
> : physical address space could potentially benefit though.  I recall some 
> : Alchemy systems may fall into this category.
> 
> The Acer Pica machines, as well as the Deskstation Tynes, had devices
> mapped outside of this range...  Of course Ralf will be able to say
> more, if he chooses to jump into the way-back machine...

 Please note that it is not the sole existence of some hardware in the 
physical address range inaccessible through the mapped space that matters 
here.  It is the need to use such a piece of hardware before paging has 
been initialised that is of concern for early ioremap() and for most 
devices it means there is no issue.

  Maciej

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