Zynq on-chip memory use

[Chris Johns]

On 22/04/2015 12:15 am, Jonathan Brandmeyer wrote:
> How does RTEMS use the On-Chip-Memory (OCM) for the Zynq? I see that
> the different BSP's map this memory differently, and that the linker
> command file for the BSP defines regions RAM_INT_0 and RAM_INT_1 for
> it.  But what goes into those regions?  Does RTEMS actually use it for
> anything?

No the OCM is not used by RTEMS. It is too specialised to be used in a
generic way.

OCM is used by the BootROM in the Zynq to load the FSBL for a couple of
reasons, first because it is the only available memory the BootROM knows
exists, and second the PL AES/HMAC decryption must always be written
back into OCM (so not externally visible on the bus). I use the OCM on a
project to decrypt user data using the PL AES/HMAC hardware (the size
limit is a pain and I have a bootgen hack to do this).

Chris