[U-Boot] Wrong RAM Size on Devkit8000

[Maxime Ripard <maxime.ripard@free-electrons.com>]

Hi Andreas,

Le 15/05/2013 09:44, Andreas Bie?mann a ?crit :
> Dear Maxime Ripard,
> 
> (CCing Board Maintainer)
> 
> On 05/14/2013 04:25 PM, Maxime Ripard wrote:
>> Hi,
>>
>> I'm currently testing u-boot 2013.04 with SPL on a Devkit8000 with 256MB
>> of RAM.
>>
>> Trouble is, it only detects 128MB of RAM. The x-loader found on the NAND
>> detects 256MB and works perfectly with it.
>>
>> I obviously tried to change the mcfg field of the timings structure to
>> be at MICRON_V_MCFG_165(256 << 20), however, while it obviously detects
>> 256MB of RAM, it then crashes quite badly when booting to a userspace
>> (and actually using that much RAM I guess). It works perfectly fine
>> though with only 128MB of RAM, so I think the timings are ok.
> 
> I guess this is linux related. We have the same problem with tricorder
> board here. Please have a look at linux kernel
> a/a/mach-omap2/board-devkit8000.c and check the following line:
> 
> ---8<---
> 	omap_sdrc_init(mt46h32m32lf6_sdrc_params,
> 				  mt46h32m32lf6_sdrc_params);
> --->8---
> 
> The mt64h32m32 is a 1Gb device which is 128MiB. I think is an leftover
> from the very beginning of these bords in linux. Maybe in former days
> the boot-loader did not initialize SDRAM correctly so it was required to
> re-write the timing registers in linux. Nowadays this should be removed.

Ouch, yes, I didn't think to look in Linux to see if it was doing some
timings configurations. Thanks for the pointer.

Now, both by changing the mentioned line in U-boot and by removing these
settings, and it seems to be working fine now.

>> Any ideas on how to solve this?
> 
> Patch u-boot to detect whether it needs to initialize 256MiB or 128MiB.
> Initialize timings correctly and remove the mentioned kernel re-timing.
> Patches are welcome (I havn't fixed the tricorder issue til now ... ;).

I'm not familiar enough yet with this board and the OMAP so that I know
how to do this right know, but I'll figure out.

Thanks,
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com