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

[Stefan Roese <sr@denx.de>]

Sun,

On Wednesday 15 April 2009, SunNeo wrote:
> I tried to add auto-calibration related configuration to my configuation
> file, but Linux still hangs at the same location. It seems error happened
> when threads of Linux Kernel tried to access the high 512m memory.

I suggest you debug this further, either by adding some printk's or using a 
debugger to see where exactly the crash happens.

> Just like the Kilauea evb, there is no ECC on my board, and I use the same
> regisger setting for DDR Controller as Kilauea. Maybe you know, Kilauea
> uses the "MT47H64M16HR" DDRII SDRAM and only one rank. My board uses the
> "MT47H256M8THN" and two ranks. So, I changed setting of MB0CF & MB1CF.

When using the 2nd rank you need to change the termination settings as well 
(SDRAM0_MODT0, SDRAM_MODT1, SDRAM0_CODT). Using the original values from 
Kilauea is definitely a problem which could lead to all kind of problems.

> I think I can confirm all 1024M memory can work well at U-Boot.

Again, you don't really know if the whole memory is working correctly just 
because you are able to boot to the U-Boot prompt. Intensive memory tests 
(with and without burst access) are necessary here.

> And if I 
> add the parameter "mem=512M" to bootargs, and set "initrd_high" to
> "20000000", Linux can boot normally.

Understood. I still think that this is a problem with incorrect SDRAM 
configuration. Take a look at the termination registers mentioned above and 
configure them correctly. 

Best regards,
Stefan

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