After the first time system_mode is set to one, the assets will no
longer be read- or writeable, even if system_mode is set to zero at a
later syscall. This is to make sure syscalls does not have the same
privilege as the firmware has at first boot.
We need to monitor when system_mode is set to one, otherwise we might
accedentially lock the assets before actually leaving firmware, for
example if firmware would use a function set in any of the registers
used in system_mode_ctrl.
Co-authored-by: Mikael Ågren <mikael@tillitis.se>
Allow FW RAM access only in the following execution contexts:
- Firmware mode
- IRQ_SYSCALL_HI
Input port `system_mode` of the `fw_ram` module is replaced with an
enable port. Since access to FW RAM not longer depend only on
system_mode
Only allow executing from ROM when in one of the following execution
contexts:
- Firmware mode
- IRQ_SYSCALL_LO
- IRQ_SYSCALL_HI
Co-authored-by: Daniel Jobson <jobson@tillitis.se>
A proof-of-concept of enabling PicoRV32 interrupts. Two interrupt
sources, which can be triggered by writes to memory addresses, are
added. The design has only been simulated, not run on hardware.
Synthesis:
Ice40 LC utilization is 93% (4934/5280) when built using tkey-builder:4
Simulation:
A `tb_application_fpga_irqpoc` target is added. Running `make
tb_application_fpga_irqpoc` creates `tb_application_fpga_sim.fst` which
can be inspected in GTKWave or Surfer.
Firmware:
A simple firmware is added in `fw/irqpoc`. It enables both interrupts
and triggers each interrupt once.
Custom PicoRV32 instructions are located in `custom_ops.S`. It is
imported from upstream PicoRV32 commit:
70f3c33ac8
