From: Clemens Koller <clemens.koller@anagramm.de>
To: u-boot@lists.denx.de
Subject: [U-Boot-Users] 85xx - DDR with ECC: Why DMA ?
Date: Thu, 11 Aug 2005 18:20:03 +0200 [thread overview]
Message-ID: <42FB7AB3.4000705@anagramm.de> (raw)
In-Reply-To: <E1E3ELh-000614-Gn@mail.sourceforge.net>
Hi, Charles!
Charles J Gillan wrote:
> Most of the work in the routine seems to concern programming the
> DMA registers rather than setting the DDR "enable" flag.
>
> Why is this DMA configuration an essential step when ECC is used and
> apparently not necessary when it is not used? I can?t see the link
> between the two.
A simple thing:
After power on, the memory content is undefined.
If you enable ECC before cleaning the whole memory and start reading
data from the memory, you will run into ECC errors over and over...
Pls. take care when you want to use the DMA on mpc85xx after u-boot
touched it for cleaning the DDR. I ran into a problem described in:
http://ozlabs.org/pipermail/linuxppc-embedded/2005-July/019196.html
Greets,
Clemens Koller
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prev parent reply other threads:[~2005-08-11 16:20 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-08-11 14:45 [U-Boot-Users] 85xx - DDR with ECC: Why DMA ? Charles J Gillan
2005-08-11 16:20 ` Clemens Koller [this message]
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