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Date: Thu, 23 Apr 2009 10:59:15 -0400
From: Josh Boyer <jwboyer@linux.vnet.ibm.com>
To: Valentine Barshak <vbarshak@ru.mvista.com>
Subject: Re: [PATCH] PPC440EPx SDRAM width
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Cc: linuxppc-dev@ozlabs.org, Stefan Roese <sr@denx.de>
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On Thu, Apr 23, 2009 at 06:40:48PM +0400, Valentine Barshak wrote:
> Stefan Roese wrote:
>> On Thursday 23 April 2009, Josh Boyer wrote:
>>> On Thu, Apr 23, 2009 at 09:36:12AM -0400, Steven A. Falco wrote:
>>>> There is an error in the way ibm4xx_denali_fixup_memsize calculates
>>>> memory size.  When testing the DDR_REDUC bit, the polarity is
>>>> backwards.  A "1" implies 32-bit wide memory while a "0" implies
>>>> 64-bit wide memory.
>>>>
>>>> For a 32-bit wide system, this bug causes twice the memory to be
>>>> reported, leading to boot failure.
>>>>
>>>> Signed-off-by: Steven A. Falco <sfalco@harris.com>
>>> So we had a previous patch for this, and a very long discussion on what the
>>> right solution was.  Either we never came to a resolution, or I have just
>>> forgotten what it was.
>>>
>>> Stefan, Valentine, do either of you remember?
>>
>
> The patch will break sequia/rainier since u-boot doesn't set the number  
> of chipselects correctly for them. IIRC, the last conversation didn't  
> come to any conclusion. We sort of wanted to fix that regardless of  
> whether we had corrected u-boot or not.
>
> Could we use a "model" property to distinguish between the "real"  
> sequoia/rainier and other custom boards?
> If yes, we could add a workaround the ibm4xx_denali_fixup_memsize to  
> hardcode the chipselect number to 1 for sequoia/rainier.

We could do that perhaps, yes.  In cases where the board has a newer U-Boot
with the fix already, it shouldn't really cause any harm, correct?

josh