From: Dan Malek <dan@mvista.com>
To: Goddeeris Frederic <Frederic.Goddeeris@siemens.atea.be>
Cc: "'ashish anand'" <ashisha@india.infogain.com>,
linuxppc-embedded@lists.linuxppc.org
Subject: Re: "Kernel logical address" vs "Physical"
Date: Fri, 14 Sep 2001 14:26:01 -0400 [thread overview]
Message-ID: <3BA24BB9.3039BD7C@mvista.com> (raw)
In-Reply-To: 6B546A602AD2D211BFF00008C7A42889041D6BE4@hrtades2.atea.be
Goddeeris Frederic wrote:
>
> So the key is that by address is above ioremap_base. That I initially got
> away with not using ioremap is a coincidence? Right?
No, it's not a coincidence. I've written sufficiently about virtual
space mapping on the embedded processors in the past and if you just
search the mailing list archives you will find all of the answers.
The short answer.....on some processors, like the 8xx, there is a
common address space used by many device drivers and functions
unique to this processor. The granularity of mapping required is
very small, resulting in many overlapped maps if you constantly use
ioremap() in all of these cases. For this processor, a common area
is ioremap()'ed by the memory management early in the kernel initialization
for all of these uses. The side effect of mapping this early is you
get a 1:1 virtual to physical mapping because the kernel VM is not
yet fully initialized.
-- Dan
** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
next prev parent reply other threads:[~2001-09-14 18:26 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-09-14 11:47 "Kernel logical address" vs "Physical" Goddeeris Frederic
2001-09-14 6:49 ` ashish anand
2001-09-14 18:26 ` Dan Malek [this message]
-- strict thread matches above, loose matches on Subject: below --
2001-09-14 12:13 Goddeeris Frederic
2001-09-14 10:52 Goddeeris Frederic
2001-09-14 6:06 ` ashish anand
2001-09-14 8:44 Goddeeris Frederic
2001-09-14 4:50 ` ashish anand
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