[U-Boot] Help!Some memory doesn't work on PPC405Ex based board!

[Grant Erickson <gerickson@nuovations.com>]

On 4/22/09 10:00 PM, SunNeo wrote:
> I got a new board with 1GB DDRII memory and only 1 Rank, but the problem still
> exist. 
>  
> The following is a summary of my job:
>
> 4. Have performed memory test with "mtest" command at U-Boot, no error
>    happened.

Sun:

It's been awhile since I looked at the code for mtest; however, it may not
be entirely comprehensive or exhaustive depending on how you configured your
u-boot build and the arguments you invoked it with. Do verify that it is
operating over the largest range of RAM possible and that it is doing an
array of tests (walking 1s, alternating bit patterns, etc.).

Also, AMCC has available (perhaps available through your FAE if not on
MyAMCC or AMCC.com itself) a DDR planning spreadsheet. While the last
revision I used had a few bugs, it certainly was useful to validate our DDR
configuration against. I'd recommend obtaining it and reviewing your
settings.

Beyond that, does the same kernel work on Kilauea? Have you set up a build
environment where you can make small, incremental changes and verify those
on Kilauea and then on your board and have confidence that only those things
you changed are changing?

Once the wrinkles got worked out of the DDR settings in the PPC405EX[r]
boards I've worked with in the last year, they all worked as well as Kilauea
without notable changes to the Linux kernel, version 2.6.25 up through
2.6.28 (all from the Denx GIT repository).

> 9. Add the parameter "mem=516M" to bootargs, Linux can boot up normally. But
> if add "mem=517M" to bootargs, Linux hangs.

That should be instructive. Start tweaking mtest or writing your own memory
tests to tease out a pattern from that. Failing that, what other values work
here? What values fail?

Regards,

Grant Erickson 
Principal
Nuovations