[U-Boot-Users] post memory test

[Detlev Zundel <dzu@denx.de>]

Hi Dongy,

> I have a question about post memory test. According to the following code, even
> if memory size is greater than 256M, only 256M memory will be tested.  Is it
> true or I missed something.  Thanks a lot.

No, this is true.  As I did not write that code, my interpretation
uses some speculation, but what is very likely the case here is that
U-Boot potentially does not map all physical available memory and thus
we cannot even access it.  As we do not have explicit variables
representing those facts, I guess the 256MB are kind of a least
common denominator.

As an example look at initdram() in board/Marvell/db64460/sdram_init.c
where the platform uses Block Address Translations (BATs) to map RAM
but exhausts these pretty scarce ressources and limits itself to
mapping only the first 256MB (a usual limit for a BAT).

> In U-BOOT-1.2.0
> u-boot\post\drivers\memory.c,

A word to version 1.2.0, if you have a platform with 256MB+ memory,
please be sure to check the fix from Aug 25 by Yuri Tikhonov "POST:
limit memory test area to not touch global data anymore" (9c02defc) in
the current code as the code in 1.2.0 caused problems on such systems.

Cheers
  Detlev

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