linux-kernel - Re: pci_fixup_video change blows up on sparc64

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Message-Id: <20061019.161749.08321831.davem@davemloft.net>
Date:	Thu, 19 Oct 2006 16:17:49 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	jesse.barnes@...el.com
Cc:	eiichiro.oiwa.nm@...achi.com, alan@...hat.com, greg@...ah.com,
	linux-kernel@...r.kernel.org
Subject: Re: pci_fixup_video change blows up on sparc64

From: Jesse Barnes <jesse.barnes@...el.com>
Date: Thu, 19 Oct 2006 15:58:05 -0700

> On Thursday, October 19, 2006 3:38 pm, David Miller wrote:
> > > Right, I guess we should have been a bit more careful in making
> > > this code generic.  At least ia64, i386 and x86_64 systems often
> > > have video BIOSes in system memory at 0xc0000 (note that this isn't
> > > in PCI space).
> >
> > Even if it is in system memory there, accessing physical RAM using
> > ioremap() and asm/io.h accessors is not exactly legal.  On sparc64,
> > for example, accessing physical RAM as if it were I/O memory will
> > result in a BUS ERROR and in fact that's how the bootup crashes
> > on sparc64 due to this changeset.
> 
> Good point, we shouldn't use ioremap for the system memory case at all.  
> Should be __va or something I guess.

That's one part, but this won't update all the pci_map_rom() callers
who use asm/io.h accessors on the mapping they get back.  Even
pci_read_rom() in the sysfs code this change was aimed at uses
memcpy_fromio().

Also, as an aside, if we're on a system where the x86 BIOS is unlikely
to be executed anyways, we should always use the PCI ROM bar mapping
to access the video card's ROM.
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