Merge #1404

1404: feat(stm32): Add DMA based, ring-buffer based rx uart, v3 r=Dirbaio a=rmja

This PR replaces #1150. Comparing to that PR, this one has the following changes:

* The implementation now aligns with the new stm32 dma module, thanks `@Dirbaio!`
* Calls to `read()` now returns on either 1) idle line, or 2) ring buffer is at most half full. This is different from the previous pr, which would return a lot of 1 byte reads. Thank you `@chemicstry` for making me realize that it was actually not what I wanted. This is accomplished using half-transfer completed and full-transfer completed interrupts. Both seems to be supported on both dma and bdma.

The implementation still have the issue mentioned here: https://github.com/embassy-rs/embassy/pull/1150#discussion_r1094627035

Regarding the todos here: https://github.com/embassy-rs/embassy/pull/1150#issuecomment-1513905925. I have removed the exposure of ndtr from `dma::RingBuffer` to the uart so that the uart now simply calls `ringbuf::reload_position()` to align the position within the ring buffer to that of the actual running dma controller. BDMA and GPDMA is not implemented. I do not have any chips with those dma controllers, so maybe someone else should to this so that it can be tested.

The `saturate_serial` test utility inside `tests/utils` has an `--idles` switch which can be used to saturate the uart from a pc, but with random idles.

Because embassy-stm32 now can have tests, we should probably run them in ci. I do this locally to test the DmaRingBuffer:  `cargo test --no-default-features --features stm32f429ig`.

cc `@chemicstry` `@Dirbaio` 


Co-authored-by: Rasmus Melchior Jacobsen <[email protected]>
Co-authored-by: Dario Nieuwenhuis <[email protected]>

2 files changed, 63 insertions, 0 deletions

diff --git a/tests/utils/Cargo.toml b/tests/utils/Cargo.toml
new file mode 100644
index 000000000..7d66fd586
--- /dev/null
+++ b/tests/utils/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "test-utils"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+rand = "0.8"
+serial = "0.4"
diff --git a/tests/utils/src/bin/saturate_serial.rs b/tests/utils/src/bin/saturate_serial.rs
new file mode 100644
index 000000000..18ca12fb7
--- /dev/null
+++ b/tests/utils/src/bin/saturate_serial.rs
@@ -0,0 +1,53 @@
+use std::path::Path;
+use std::time::Duration;
+use std::{env, io, process, thread};
+
+use rand::random;
+use serial::SerialPort;
+
+pub fn main() {
+    if let Some(port_name) = env::args().nth(1) {
+        let idles = env::args().position(|x| x == "--idles").is_some();
+
+        println!("Saturating port {:?} with 115200 8N1", port_name);
+        println!("Idles: {}", idles);
+        println!("Process ID: {}", process::id());
+        let mut port = serial::open(&port_name).unwrap();
+        if saturate(&mut port, idles).is_err() {
+            eprintln!("Unable to saturate port");
+        }
+    } else {
+        let path = env::args().next().unwrap();
+        let basepath = Path::new(&path).with_extension("");
+        let basename = basepath.file_name().unwrap();
+        eprintln!("USAGE: {} <port-name>", basename.to_string_lossy());
+    }
+}
+
+fn saturate<T: SerialPort>(port: &mut T, idles: bool) -> io::Result<()> {
+    port.reconfigure(&|settings| {
+        settings.set_baud_rate(serial::Baud115200)?;
+        settings.set_char_size(serial::Bits8);
+        settings.set_parity(serial::ParityNone);
+        settings.set_stop_bits(serial::Stop1);
+        Ok(())
+    })?;
+
+    let mut written = 0;
+    loop {
+        let len = random::<usize>() % 0x1000;
+        let buf: Vec<u8> = (written..written + len).map(|x| x as u8).collect();
+
+        port.write_all(&buf)?;
+
+        if idles {
+            let micros = (random::<usize>() % 1000) as u64;
+            println!("Sleeping {}us", micros);
+            port.flush().unwrap();
+            thread::sleep(Duration::from_micros(micros));
+        }
+
+        written += len;
+        println!("Written: {}", written);
+    }
+}