FSBL 192KB limit

Question

According to the documentation, there is a 192 KB limit on the size of the FSBL (or at least the size which can be loaded into on-chip memor, "The size of the FSBL loaded into OCM is limited to 192 kilobyte").

Unfortunately we need to add some code into the FSBL which pushes the size beyond this limit.

What is the proper workaround so you can utilize the full 256 KB in the FSBL?

Has anyone done this?

I can think of a few hypothetical solutions, but none are very appealing:

1. Make a relocatable library which gets loaded into RAM by the FSBL. (This would have a lot of nasty details, including that entry points would keep changing on each compile. There's no DLL infrastructure to help.)

2. Make a really tiny FSBL that loads our full FSBL.

Is it possible to exceed the 192 KB with code which is not critical to the inital startup tasks?

Thanks for all help!

Stuart

Former Member · Accepted Answer

There is another option, if you have QSPI or NOR bootable Flash in your system. Zynq supports a feature call "Execute-In-Place", which allows the FSBL code to be directly executed from the QSPI or NOR Flash without copying the code into the on-chip RAM. This will remove the 192KB code size limitation. The following link might be useful in implementing/using the Execute-In-Place feature.

http://www.wiki.xilinx.com/Zynq-7000+AP+SoC+DDRLess+System+Tech+Tip