linux-kernel - Re: [PATCH] [PowerPC] MPC8272ADS: fix device tree for 8 MB flash, size

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Date:	Fri, 15 May 2009 07:54:51 +0200
From:	Heiko Schocher <hs@...x.de>
To:	Scott Wood <scottwood@...escale.com>
CC:	Wolfgang Denk <wd@...x.de>, linuxppc-dev@...abs.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [PowerPC] MPC8272ADS: fix device tree for 8 MB flash,
 size

Hello Scott,

Scott Wood wrote:
> On Wed, May 13, 2009 at 08:27:07AM +0200, Heiko Schocher wrote:
>> Hello Wolfgang,
>>
>>> The current device tree for the MPC8272ADS assumes a mapping of 32 MB
>>> of NOR flash at 0xFE00.0000, while there are actually only 8 MB on
>>> the boards, mapped at 0xFF80.0000. When booting an uImage with such a
>>> device tree, the kernel crashes because 0xFE00.0000 is not mapped.
>> Wouldn;t it be better, if u-boot fixes the device tree entries?
> 
> We should proabbly leave out the ranges altogether, and have u-boot
> populate it from the mappings it establishes.

No, I vote for manipulating just the entries, which u-boot dynamically
detect, and let the other entries untouched. It is possible that
there is a device which u-boot didn;t use/know, and there is in the DTS
an ranges entry for it (Maybe not on the MPC8727ADS, but we should
define a rule, how a bootloader has to manipulate entries). So if
u-boot build the complete ranges entry, it maybe miss something.

>> I think, u-boot should know, where the flash begins and ends, and
>> because this is maybe a dynamic variable for this board, it should
>> be better, if u-boot fixes this, so no need for adding a device tree
>> for every board variant.
> 
> Flash is on a SIMM on this board, and the board manual says it's
> expandable to 32 MiB.  However, I suspect that the current DTS was just
> an error as I based it on a board that had not had its flash SIMM
> modified.  That specific flash SIMM is no longer working (or perhaps just
> got its contents corrupted -- one of these days I may hook up a BDI and
> try to reflash), so I can't go back and check.
> 
> I don't see how current u-boot would accomodate more than 8MiB flash on
> this board (there's some detection in board/freescale/mpc8260ads/flash.c,

Didn;t this board uses the CFI driver? :-(

> but I don't see any setting of BR0 besides the preliminary value at
> 0xff800000).

OK, then the patch from Wolfgang should be sufficient.

bye
Heiko
-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
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