am335x evm RAM memory

Check the bootargs "mem=" field.

I saw that, but this value was manually write. If I change the value to 512MB, will the SDRAM driver be able to use all memory correctly? In u-boot happens the same thing, the value is manually write in a config file, just change it? I know that in u-boot this value isn't important, my doubt is mainly in kernel.

Thanks,

Leonardo

Prates,

If not 512MB can you try at least mem=400M and see whether it works for you or not.