linux-kernel - Re: [PULL] Add support for Texas Instruments C6X architecture

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Date:	Sun, 06 Nov 2011 15:05:27 -0500
From:	Mark Salter <msalter@...hat.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	Arnd Bergmann <arnd@...db.de>
Subject: Re: [PULL] Add support for Texas Instruments C6X architecture

On Sun, 2011-11-06 at 11:07 -0800, Linus Torvalds wrote:
> >
> > I think the best counter argument is that it leads to paddr != vaddr
> > in the case of NOMMU with a non-zero memory base. My view is that in
> > all NOMMU cases, physical and virtual addresses should be the same.
> > Otherwise, you end up breaking drivers which need to pass physical
> > addresses to devices.
> 
> That's a totally insane argument.

Not *totally* insane. Forget the last sentence. You're right that its a
driver problem. Creating a physical address space separate from the
"virtual" space on a NOMMU arch where the hw uses a one-to-one mapping
seems a long way to go. My point here is that the simplest NOMMU case is
paddr == vaddr. Right now, the generic headers are broken in that regard
for hardware that maps RAM at a non-zero address.

So, okay. Let's have some more discussion among more people. There is
certainly more than one approach to fix the currently broken bits and I
sure don't claim to have the one true way. I just want to do what needs
to be done to make the port acceptable for upstream inclusion.

--Mark

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