c44f117331
- fix tx_await() condition to consider both control and tx channels - make tx_async more efficient for the common case that the buffer fits in a single transaction by appending the CS de-assert as part of the initial command stream - make trait for the udma global clock setting The high bit in this exploration is that there seems to be no way to actually confirm when a UDMA transaction has fully completed on the hardware interface. All the completion signals tell you when the software-side UDMA resources are freed up. However, in this case, the hardware-side resources may still be transmitting/receiving data. This is a problem for the case of a '4-wire SPI' display where you need to set an extra line to control command/data mode addressing. In this case, the current work-around is to read back the state of the chip select pin as a GPIO to determine when the hardware has finished. I suspect that if we can figure out how to use UDMA in a full duplex mode that we could do something more essentially linked to the hardware, but this would also require having a dummy Rx buffer allocated that is the same depth as the hardware Tx buffer if all you cared about is the hardware conclusion of a Tx. |
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|---|---|---|
| .. | ||
| bin | ||
| curve25519-dalek-loader | ||
| ed25519-dalek-loader | ||
| sha2-loader | ||
| src | ||
| test | ||
| .gitignore | ||
| build.rs | ||
| Cargo.toml | ||
| LICENSE | ||
| link.x | ||
| README.md | ||
Xous Stage 1 Loader
This contains the stage1 for Xous. This program is responsible for parsing the initial boot arguments, setting up memory maps, and preparing the kernel and its initial programs to run.
This program runs in Machine mode and has access to the entire system. When it jumps to the kernel, the system will be in Supervisor mode with no way to return to Machine mode.
Building
To build the stage-1 module, you will need a riscv32i-unknown-none-elf
or riscv32imac-unknown-none-elf target for Rust.
- Decide what target you want. For simple, embedded systems this could
be
riscv32i-unknown-none-elf, and for more complex systems with compressed instructions you could useriscv32imac-unknown-none-elf. - Get Rust. Go to https://rustup.rs/ and follow its instructions.
- Install the proper toolchain:
rustup target add ${target_arch} - Build the stage-1 loader:
cargo build --release --target ${target_arch} - Get an executable binary:
riscv64-unknown-elf-gcc -O binary target/${target}/xous-stage1 xous-stage1.bin
If you have made changes to the assembly trampoline which sets up
the loader, you will need to manually rebuild this, by running assemble.sh.
This will replace a set of objects in the bin directory.
Using
This requires additional components in order to function:
- A kernel to run, and optionally additional init processes
- A kernel arguments structure to indicate memory regions
- A stage-0 bootloader to set up the arguments
The stage-0 bootloader needs to load the kernel arguments structure into
memory at some address, then set register $a0 (also known as $x10 or
R10 in RISC-V) to point there. It then needs to jump to that address.
For example, in Renode, this is accomplished with the following commands:
sysbus LoadELF @../stage1/target/riscv32i-unknown-none-elf/debug/xous-stage1
sysbus LoadBinary @../tools/args.bin 0x40800000
# Set $a0 to point at the args binary
cpu SetRegisterUnsafe 10 0x40800000
cpu PC 0x20500000
There is no additional setup required.
Testing
Because xous-stage1 spends much of its time setting up pagetables for
RV32, it depends on a system with 32-bit pointers. If you attempt to
run it on a system with 64-bit pointers, it will panic.
The easy solution is to install a 32-bit toolchain and test with that.
To get a list of possible toolchains, run rustc --print target-list
and pick one that starts with i686-, armv7-, or some other 32-bit
arch.
$ rustup target add i686-unknown-linux-musl
15:26:39 info: downloading component 'rust-std' for 'i686-unknown-linux-musl'
15:26:41 info: installing component 'rust-std' for 'i686-unknown-linux-musl'
$
To run tests, use cargo --test. For example:
❯ cargo test --target i686-pc-windows-msvc
Compiling lazy_static v1.4.0
Compiling xous-stage1 v0.1.0 (D:\\Code\\Xous\\stage1)
Finished test [unoptimized + debuginfo] target(s) in 6.32s
Running target\\i686-pc-windows-msvc\\debug\\deps\\xous_stage1-4e16f995c7c21520.exe
running 6 tests
test test::copy_processes ... ok
test test::full_boot ... ok
test test::allocate_regions ... ok
test test::parse_args_bin ... ok
test test::read_initial_config ... ok
test test::tracker_sane ... ok
test result: ok. 6 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out
❯
Contribution Guidelines
Please see CONTRIBUTING for details on how to make a contribution.
Please note that this project is released with a Contributor Code of Conduct. By participating in this project you agree to abide its terms.
License
Copyright © 2020
Licensed under the Apache License 2.0 LICENSE