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From: Shawn Jin <shawnxjin@gmail.com>
To: ppcembed <linuxppc-embedded@ozlabs.org>
Subject: Question on fixup_bigphys_addr() in syslib/ibm44x_common.c
Date: Fri, 15 Apr 2005 17:16:32 -0700	[thread overview]
Message-ID: <c3d0340b05041517167c0cfa5c@mail.gmail.com> (raw)

Hi,

When looking into ppc440 support, I'm confused on the functionality of
fixup_bigphys_addr() in syslib/ibm44x_common.c. It's called by
ioremap() in arch/ppc/mm/pgtable.c. The prototype is as follows.
     phys_addr_t fixup_bigphys_addr(phys_addr_t addr, phys_addr_t size)

Why do we need this fixup? ioremap() takes a physical address as an
argument and maps the physical address space to virtual address space
with the specified size. Since it's already a physical address, which
is 36-bit address in the case of 440, why do we need to fix up the
ERPN? I must be missing something here.

Thanks,
-Shawn.

             reply	other threads:[~2005-04-16  0:16 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2005-04-16  0:16 Shawn Jin [this message]
2005-04-16  0:36 ` Question on fixup_bigphys_addr() in syslib/ibm44x_common.c Eugene Surovegin

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