With this bootcode.bin running on the VPU, after the ARM starts up and Linux is loaded, does the VPU halt and remain unreachable, or does the "normal" VC4 RTOS execute such that stuff from the ARM can be mailboxed to it?
Currently it sleeps and waits for a mailbox interrupt after which it acks it and goes back to sleep. We're planning on using the interface to load a second stage firmware that would emulate the closed source firmware's power/clock management interfaces (but not framebuffer/PV/HVS/HDMI related stuff since there are Linux drivers for that now).