j820, the saga

Oleg Gusev oleg@usm.uni-muenchen.de
Sun Mar 28 01:15:22 CET 2004

>(though, if the RAM bank 1 has 2MB of VRAM, couldn't RAM bank 2 or 3
>hold something else than 16MB of RAM?

The VRAM is _physically_ on sa1101, and is visible "logically"
only for writing as a bank 1. Done with a hardware wizardry.
It can be probably seen as a 16MB RAM too, while the writes 
above 2MB are trapped by the kernel ? What really happens
when you read/write the nonexistent memory? Should cause
a bus fault, that should be handled by the kernel. This is
too lowlevel for me right now.

>* we need know the size of the initrd, which must be quite separate
> from the zImage.
>* we need know the size and location of memory and initrd,
> which the booting.php clearly tells us is a task for the boot loader.
>* this j820/init.S can be construed as the last part of the bootloader.

Ok, then we need to move all this code into the bootloader.

> if you know how to reset all internal IO registers, go ahead!

I will try to write these things down in a half-human-readable form.


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