[U-Boot] Issues with memory mapping for AT91SAM9G25-EK

[Vasi Vilvoiu]

Hello,

I'm trying to use AT91SAM9G25-EK board for machine learning. One of the
reasons I chose this board, besides it targeting ARM9 which was my focus,
is that is has 1GB of RAM.

I've used the following guide to setup a Debian installation:
https://eewiki.net/display/linuxonarm/AT91SAM9x5

The gist of it is, I'm using AT91Bootstrap as a first stage bootloader and
u-boot as a second stage.

I'm compiling from github (branch v2016.07-rc2) and patching it with the
following:
https://rcn-ee.com/repos/git/u-boot-patches/v2016.07-rc2/0001-at91sam9x5ek-uEnv.txt-bootz-n-fixes.patch

Everything works well, but linux cannot see more than 128MB of the memory.

I'm (almost) a complete noob when it comes to embedded programming, but
what I understood so far is that u-boot defines the memory layout in the
configuration files. Sure enough, I found the definitions that limit the
memory being used:
https://github.com/u-boot/u-boot/blob/master/include/configs/at91sam9x5ek.h

Could I please get some help adjusting it in order to use all available
memory? I tried changing CONFIG_SYS_SDRAM_SIZE to 512MB (0x20000000) and it
won't boot. Also changing "fdtaddr" (which I have no idea what it does) in
CONFIG_EXTRA_ENV_SETTINGS to "fdtaddr=0x39FF0000" yields the same result.

For the moment I lack a RS232 port on my dev machine, so I can't give you
more insight into what fails. But I'm obviously doing something horribly
wrong here, so if you could give me some tips or point me to some relevant
documentation, I would be grateful.

Thank you!
Vasile Vilvoiu




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*Vasile Vilvoiu*
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