Restrict bus crossbar access by region mode

[jdavidberger]

I'm working with a vexrisc design and I want to restrict the instruction bus to only look at regions which can contain executable code. This isn't so much for security reasons as it is for routing reasons -- I'll never need to execute out of RTL registers(or RAM, really) set up for this application and want to snip those logic paths out.

Is there existing support to do this or plans to add it? I hacked something into my branch but I don't think it's mergable -- I had to change how crossbar instantiations were called to filter out regions I didn't want.

[enjoy-digital]

Hi @jdavidberger,

there is not current support for this but could indeed be an interesting feature. Currently, the Bus Master are only limited by the address width but we could see how to restrict access to a specific location. Maybe the recent Wishbone/AXIRemapper module could help or be reused for this. Feel free to share your changes.