PoC: Implement syscalls using PicoRV32 interrupts #305
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agren
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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: YosysHQ/picorv32@70f3c33
Add example firmware for demoing interrupts on Tkey hardware.
Instead of manually switching to app mode using the system mode register, app mode will be enabled when executing outside of firmware ROM. Co-authored-by: Mikael Ågren <[email protected]>
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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 <[email protected]>
Adds a basic example firmware that copies an app to app RAM. The app triggers syscall interrupts and tries to execute ROM code from app mode. A make target (`tb_application_fpga_irqpoc_with_app`) that simulates a Tkey running the firmware is added.
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
…ed in C App is embedded in firmware and is loaded into app RAM when firmware starts. App continuously calls SET_LED syscalls. Simulation: `make tb_application_fpga_irqpoc_c_example`
Co-authored-by: Mikael Ågren <[email protected]>
…is set 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 <[email protected]>
Removing IRQ30 since it us no longer exist
Removing IRQ30 since it us no longer exist
Removing IRQ30 since it us no longer exist
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Removing IRQ30 since it us no longer exist
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dehanj
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Dec 18, 2024
| @@ -291,7 +293,7 @@ module tk1 #( | |||
| gpio2_reg[1] <= gpio2_reg[0]; | |||
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| if (system_mode_we) begin | |||
| system_mode_reg <= 1'h1; | |||
| system_mode_reg <= system_mode_new; | |||
There was a problem hiding this comment.
I think we should keep system_mode_reg <= 1'h1;
Then we can remove system_mode_new completely. Since what I can see we never return to system_mode_reg = 0.
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Description
This is a proof of concept of using PicoRV32 interrupts to implement syscalls.
The idea is to let in app execute system calls by raising an interrupt. The
following sequence describes a syscall call:
instruction
retirq.One interrupt is added: IRQ31. An interrupt is triggered by writing
to a specific memory area. Triggering an interrupt hands over execution to the interrupt handler in firmware ROM (address 0x10).
The PicoRV32
eoisignal is used to make certain resources, which are otherwise unavailable in app mode, available to the interrupt handler.Four example firmwares are available to demonstrate interrupt handling:
Added so far:
This draft PR is part of investigating #234.