linux-kernel - Re: pxa300

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Message-Id: <201006072143.16136.marek.vasut@gmail.com>
Date:	Mon, 7 Jun 2010 21:43:16 +0200
From:	Marek Vasut <marek.vasut@...il.com>
To:	Mike Rapoport <mike.rapoport@...il.com>
Cc:	balakrishnan <balakrishnan@...onsystems.com>,
	Maharajan <maharajan@...onsystems.com>,
	Eric Miao <eric.y.miao@...il.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: pxa300 - DDRAM base value

Dne Po 7. června 2010 21:37:16 Mike Rapoport napsal(a):
> > hi,
> >       Now, I can able to boot after editing following files
> > arch/arm/mach-pxa/Makefile.boot and
> > arch/arm/mach/pxa/include/mach/memory.h (0x80000000 changed to
> > 0xa0000000). My doubt is
> > 1.why 0x80000000 (DDR phy address) is aliased to 0xa0000000 in pxa
> > architecture?
> > 2.In my development board two DDRAMs mapped at 0x80000000-0x88000000 and
> > 0xc0000000-0xc8000000, how can I inform to kernel about this different
> > bank and size?.
> 
> enable CONFIG_HIGHMEM

Mike, that wont help him as he has PHYS_OFFSET=0xa0000000 . Selecting 
CONFIG_HIGHMEM will only cause the pages for RAM below 0xa0000000 to have 
incorrectly computated descriptor addresses (or maybe will be ignored).

The page descriptors for RAM at PA 0xa0000000 are at VA 0xc0000000 + some offset 
(there's an easy linear formula to compute their offset). Now if you feed that 
formula with 0x80000000, the page descriptors will end below 0xc0000000, which 
isn't a valid VA, therefore the descriptors will not be valid either (in the 
better case, but it will hang the kernel at early stage anyway).

Therefore there are two ways -- either use what I suggested earlier or wait 
until the PHYS_OFFSET is dynamically computated (check Eric's patchset).

Cheers
> 
> > My Boot loader details,
> > ------------------------------
> > =>bdi
> > arch_number = 0x00000B04
> > env_t       = 0x00000000
> > boot_params = 0x80000100
> > DRAM bank   = 0x00000000
> > -> start    = 0x80000000
> > -> size     = 0x08000000
> > DRAM bank   = 0x00000001
> > -> start    = 0xC0000000
> > -> size     = 0x08000000
> > ethaddr     = 08:00:3e:26:0a:5b
> > ip_addr     = 192.168.0.21
> > baudrate    = 115200 bps
> > =>ver
> > U-Boot 2010.03 (Jun 01 2010 - 14:27:43)
> > 
> > 
> > With Thanks
> > J.Balakrishnan
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel@...ts.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
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