From: Norbert van Bolhuis <nvbolhuis@aimvalley•nl>
To: Frank Prepelica <Frank.Prepelica@ubidyne•com>
Cc: linuxppc-dev@lists•ozlabs.org
Subject: Re: How to set DDR data bus width to 16Bit
Date: Thu, 02 Jul 2009 11:04:18 +0200 [thread overview]
Message-ID: <4A4C7812.7040301@aimvalley.nl> (raw)
In-Reply-To: <29DC34A6B43468409F5A371CFE34E849D7F173@ex01.ads.ubidyne.de>
you have to do it via your bootloader (u-boot) which sets up
the DDR memory controller.
Linux (already) assumes memory is available.
Are you sure linux kernel is changing DDR_SDRAM_CFG ?
When our linux-2.6.28 kernel is up, it's still 0xc3080000 when I read
physical address 0xe0002110.
Btw. We did some performance tests with 16 bit bus-width (DDR2 memory)
and surprisingly performance was almost as good as 32 bit bus-width
---
N. van Bolhuis.
Frank Prepelica wrote:
> Hi all,
>
> Does anyone knows how to set the DDR data bus width to 16Bit in linux?
> I've found that
> option in U-Boot in the MPC8313ERDB_config file. (verfied with a memory
> dump of the
> CPU register (DDR_SDRAM_CFG) - the 16Bit DBW is set(10b) ). But after
> starting
> linux the value is set to 00b (=reseverd).
>
> We are using a customized MPC8313ERDB board.
>
> Thanks in advance
>
>
> Kind regards
>
> Frank Prepelica
> Software Design Engineer
>
> Ubidyne GmbH
> Lise-Meitner-Str.-14
> 89081 Ulm - Germany
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev@lists•ozlabs.org
> https://lists.ozlabs.org/listinfo/linuxppc-dev
>
prev parent reply other threads:[~2009-07-02 9:10 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-07-02 8:17 How to set DDR data bus width to 16Bit Frank Prepelica
2009-07-02 9:04 ` Norbert van Bolhuis [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4A4C7812.7040301@aimvalley.nl \
--to=nvbolhuis@aimvalley$(echo .)nl \
--cc=Frank.Prepelica@ubidyne$(echo .)com \
--cc=linuxppc-dev@lists$(echo .)ozlabs.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox