linux-kernel - Re: [PATCH] arm: add default value for PHYS

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Date:	Fri, 2 Dec 2011 14:27:04 -0500 (EST)
From:	Nicolas Pitre <nicolas.pitre@...aro.org>
To:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
cc:	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	linux-arm-kernel@...ts.infradead.org,
	Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm: add default value for PHYS_OFFSET Kconfig setting

On Fri, 2 Dec 2011, Uwe Kleine-König wrote:

> Hello,
> 
> On Fri, Dec 02, 2011 at 11:31:50AM -0500, Paul Gortmaker wrote:
> > On 11-12-02 04:21 AM, Uwe Kleine-König wrote:
> > > Hello Nicolas,
> > > 
> > > On Fri, Dec 02, 2011 at 12:33:26AM -0500, Nicolas Pitre wrote:
> > 
> > [...]
> > 
> > >> And it seems that at91x40 is the only defconfig with MMU=n, so the only 
> > >> option is really to provide a default CONFIG_PHYS_OFFSET.  So what about 
> > >> this:
> > >>
> > >> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> > >> index e084b7e981..a24672924f 100644
> > >> --- a/arch/arm/Kconfig
> > >> +++ b/arch/arm/Kconfig
> > >> @@ -222,6 +222,7 @@ config NEED_MACH_MEMORY_H
> > >>  config PHYS_OFFSET
> > >>  	hex "Physical address of main memory"
> > >>  	depends on !ARM_PATCH_PHYS_VIRT && !NEED_MACH_MEMORY_H
> > >> +	default DRAM_BASE if !MMU
> > >>  	help
> > >>  	  Please provide the physical address corresponding to the
> > >>  	  location of main memory in your system.
> > >>
> > >> Eventually the DRAM_BASE config option could simply be replaced by 
> > >> PHYS_OFFSET directly, but that's a larger change.
> > > I'm working on a MMU-less machine, too and had that change already in my
> > > working copy. I was about to commit and it send out later today.
> > > 
> > > So: Acked-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> > 
> > Looks fine to me as well; I had no particular attachment to the
> > original patch, and you guys have a much better understanding of
> > the specifics of the system.
> A post-ack comment: would it make sense to make this:
> 
> 	config PHYS_OFFSET
> 		hex "Physical address of main memory" if MMU
> 	...
> 
> such that !MMU build don't get a chance to misconfigure it?

Sure.


Nicolas