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
Add incoming and outgoing CTS (Clear To Send) signals for the FPGA to
let the CH552 and FPGA signal each other that it is OK to send UART
data. The CTS signals indicate "OK to send" if high. If an incoming
CTS signal goes low, the receiver of that signal should immediatly
stop sending UART data.
- Extend hardware checks for invalid memory accesses to include
checking more address space.
- In fw include file: fix two typos for memory ranges that relates to
above that fortunately have no impact on functionality.
