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stm32/uart: refactor rx ringbuffer

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- remove some race conditions
- allow full use of rx buffer
This commit is contained in:
xoviat
2023-05-29 14:49:43 -05:00
parent 0a136c308e
commit aba0f8fd6c
7 changed files with 422 additions and 424 deletions
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50
embassy-stm32/src/usart/mod.rs
View File

@ -13,6 +13,12 @@ use futures::future::{select, Either};
use crate::dma::{NoDma, Transfer};
use crate::gpio::sealed::AFType;
#[cfg(not(any(usart_v1, usart_v2)))]
#[allow(unused_imports)]
use crate::pac::usart::regs::Isr as Sr;
#[cfg(any(usart_v1, usart_v2))]
#[allow(unused_imports)]
use crate::pac::usart::regs::Sr;
#[cfg(not(any(usart_v1, usart_v2)))]
use crate::pac::usart::Lpuart as Regs;
#[cfg(any(usart_v1, usart_v2))]
use crate::pac::usart::Usart as Regs;
@ -32,7 +38,6 @@ impl<T: BasicInstance> interrupt::Handler<T::Interrupt> for InterruptHandler<T>
let (sr, cr1, cr3) = unsafe { (sr(r).read(), r.cr1().read(), r.cr3().read()) };
let mut wake = false;
let has_errors = (sr.pe() && cr1.peie()) || ((sr.fe() || sr.ne() || sr.ore()) && cr3.eie());
if has_errors {
// clear all interrupts and DMA Rx Request
@ -52,35 +57,24 @@ impl<T: BasicInstance> interrupt::Handler<T::Interrupt> for InterruptHandler<T>
w.set_dmar(false);
});
}
} else if cr1.idleie() && sr.idle() {
// IDLE detected: no more data will come
unsafe {
r.cr1().modify(|w| {
// disable idle line detection
w.set_idleie(false);
});
}
} else if cr1.rxneie() {
// We cannot check the RXNE flag as it is auto-cleared by the DMA controller
wake = true;
// It is up to the listener to determine if this in fact was a RX event and disable the RXNE detection
} else {
if cr1.idleie() && sr.idle() {
// IDLE detected: no more data will come
unsafe {
r.cr1().modify(|w| {
// disable idle line detection
w.set_idleie(false);
});
}
wake = true;
}
if cr1.rxneie() {
// We cannot check the RXNE flag as it is auto-cleared by the DMA controller
// It is up to the listener to determine if this in fact was a RX event and disable the RXNE detection
wake = true;
}
return;
}
if wake {
compiler_fence(Ordering::SeqCst);
s.rx_waker.wake();
}
compiler_fence(Ordering::SeqCst);
s.rx_waker.wake();
}
}
@ -1109,9 +1103,9 @@ pub use crate::usart::buffered::InterruptHandler as BufferedInterruptHandler;
mod buffered;
#[cfg(not(gpdma))]
mod rx_ringbuffered;
mod ringbuffered;
#[cfg(not(gpdma))]
pub use rx_ringbuffered::RingBufferedUartRx;
pub use ringbuffered::RingBufferedUartRx;
use self::sealed::Kind;

182
embassy-stm32/src/usart/rx_ringbuffered.rs → embassy-stm32/src/usart/ringbuffered.rs
View File

@ -2,13 +2,12 @@ use core::future::poll_fn;
use core::sync::atomic::{compiler_fence, Ordering};
use core::task::Poll;
use embassy_hal_common::drop::OnDrop;
use embassy_hal_common::PeripheralRef;
use futures::future::{select, Either};
use super::{clear_interrupt_flags, rdr, sr, BasicInstance, Error, UartRx};
use crate::dma::ringbuffer::OverrunError;
use crate::dma::RingBuffer;
use crate::usart::{Regs, Sr};
pub struct RingBufferedUartRx<'d, T: BasicInstance, RxDma: super::RxDma<T>> {
_peri: PeripheralRef<'d, T>,
@ -24,7 +23,9 @@ impl<'d, T: BasicInstance, RxDma: super::RxDma<T>> UartRx<'d, T, RxDma> {
let request = self.rx_dma.request();
let opts = Default::default();
let ring_buf = unsafe { RingBuffer::new_read(self.rx_dma, request, rdr(T::regs()), dma_buf, opts) };
RingBufferedUartRx {
_peri: self._peri,
ring_buf,
@ -42,11 +43,18 @@ impl<'d, T: BasicInstance, RxDma: super::RxDma<T>> RingBufferedUartRx<'d, T, RxD
Ok(())
}
fn stop(&mut self, err: Error) -> Result<usize, Error> {
self.teardown_uart();
Err(err)
}
/// Start uart background receive
fn setup_uart(&mut self) {
// fence before starting DMA.
compiler_fence(Ordering::SeqCst);
// start the dma controller
self.ring_buf.start();
let r = T::regs();
@ -58,8 +66,8 @@ impl<'d, T: BasicInstance, RxDma: super::RxDma<T>> RingBufferedUartRx<'d, T, RxD
w.set_rxneie(false);
// enable parity interrupt if not ParityNone
w.set_peie(w.pce());
// disable idle line interrupt
w.set_idleie(false);
// enable idle line interrupt
w.set_idleie(true);
});
r.cr3().modify(|w| {
// enable Error Interrupt: (Frame error, Noise error, Overrun error)
@ -72,6 +80,8 @@ impl<'d, T: BasicInstance, RxDma: super::RxDma<T>> RingBufferedUartRx<'d, T, RxD
/// Stop uart background receive
fn teardown_uart(&mut self) {
self.ring_buf.request_stop();
let r = T::regs();
// clear all interrupts and DMA Rx Request
// SAFETY: only clears Rx related flags
@ -93,9 +103,6 @@ impl<'d, T: BasicInstance, RxDma: super::RxDma<T>> RingBufferedUartRx<'d, T, RxD
}
compiler_fence(Ordering::SeqCst);
self.ring_buf.request_stop();
while self.ring_buf.is_running() {}
}
/// Read bytes that are readily available in the ring buffer.
@ -111,96 +118,49 @@ impl<'d, T: BasicInstance, RxDma: super::RxDma<T>> RingBufferedUartRx<'d, T, RxD
// Start background receive if it was not already started
// SAFETY: read only
let is_started = unsafe { r.cr3().read().dmar() };
if !is_started {
self.start()?;
}
match unsafe { r.cr3().read().dmar() } {
false => self.start()?,
_ => {}
};
// SAFETY: read only and we only use Rx related flags
let s = unsafe { sr(r).read() };
let has_errors = s.pe() || s.fe() || s.ne() || s.ore();
if has_errors {
self.teardown_uart();
if s.pe() {
return Err(Error::Parity);
} else if s.fe() {
return Err(Error::Framing);
} else if s.ne() {
return Err(Error::Noise);
} else {
return Err(Error::Overrun);
}
}
self.ring_buf.reload_position();
match self.ring_buf.read(buf) {
Ok(len) if len == 0 => {}
Ok(len) => {
assert!(len > 0);
return Ok(len);
}
Err(OverrunError) => {
// Stop any transfer from now on
// The user must re-start to receive any more data
self.teardown_uart();
return Err(Error::Overrun);
}
}
check_for_errors(clear_idle_flag(T::regs()))?;
loop {
self.wait_for_data_or_idle().await?;
match self.ring_buf.read(buf) {
Ok((0, _)) => {}
Ok((len, _)) => {
return Ok(len);
}
Err(_) => {
return self.stop(Error::Overrun);
}
}
self.ring_buf.reload_position();
if !self.ring_buf.is_empty() {
break;
match self.wait_for_data_or_idle().await {
Ok(_) => {}
Err(err) => {
return self.stop(err);
}
}
}
let len = self.ring_buf.read(buf).map_err(|_err| Error::Overrun)?;
assert!(len > 0);
Ok(len)
}
/// Wait for uart idle or dma half-full or full
async fn wait_for_data_or_idle(&mut self) -> Result<(), Error> {
let r = T::regs();
// make sure USART state is restored to neutral state
let _on_drop = OnDrop::new(move || {
// SAFETY: only clears Rx related flags
unsafe {
r.cr1().modify(|w| {
// disable idle line interrupt
w.set_idleie(false);
});
}
});
// SAFETY: only sets Rx related flags
unsafe {
r.cr1().modify(|w| {
// enable idle line interrupt
w.set_idleie(true);
});
}
compiler_fence(Ordering::SeqCst);
let mut dma_init = false;
// Future which completes when there is dma is half full or full
let dma = poll_fn(|cx| {
self.ring_buf.set_waker(cx.waker());
compiler_fence(Ordering::SeqCst);
let status = match dma_init {
false => Poll::Pending,
true => Poll::Ready(()),
};
self.ring_buf.reload_position();
if !self.ring_buf.is_empty() {
// Some data is now available
Poll::Ready(())
} else {
Poll::Pending
}
dma_init = true;
status
});
// Future which completes when idle line is detected
@ -210,28 +170,11 @@ impl<'d, T: BasicInstance, RxDma: super::RxDma<T>> RingBufferedUartRx<'d, T, RxD
compiler_fence(Ordering::SeqCst);
// SAFETY: read only and we only use Rx related flags
let sr = unsafe { sr(r).read() };
// Critical section is needed so that IDLE isn't set after
// our read but before we clear it.
let sr = critical_section::with(|_| clear_idle_flag(T::regs()));
// SAFETY: only clears Rx related flags
unsafe {
// This read also clears the error and idle interrupt flags on v1.
rdr(r).read_volatile();
clear_interrupt_flags(r, sr);
}
let has_errors = sr.pe() || sr.fe() || sr.ne() || sr.ore();
if has_errors {
if sr.pe() {
return Poll::Ready(Err(Error::Parity));
} else if sr.fe() {
return Poll::Ready(Err(Error::Framing));
} else if sr.ne() {
return Poll::Ready(Err(Error::Noise));
} else {
return Poll::Ready(Err(Error::Overrun));
}
}
check_for_errors(sr)?;
if sr.idle() {
// Idle line is detected
@ -243,11 +186,7 @@ impl<'d, T: BasicInstance, RxDma: super::RxDma<T>> RingBufferedUartRx<'d, T, RxD
match select(dma, uart).await {
Either::Left(((), _)) => Ok(()),
Either::Right((Ok(()), _)) => Ok(()),
Either::Right((Err(e), _)) => {
self.teardown_uart();
Err(e)
}
Either::Right((result, _)) => result,
}
}
}
@ -257,6 +196,37 @@ impl<T: BasicInstance, RxDma: super::RxDma<T>> Drop for RingBufferedUartRx<'_, T
self.teardown_uart();
}
}
/// Return an error result if the Sr register has errors
fn check_for_errors(s: Sr) -> Result<(), Error> {
if s.pe() {
Err(Error::Parity)
} else if s.fe() {
Err(Error::Framing)
} else if s.ne() {
Err(Error::Noise)
} else if s.ore() {
Err(Error::Overrun)
} else {
Ok(())
}
}
/// Clear IDLE and return the Sr register
fn clear_idle_flag(r: Regs) -> Sr {
unsafe {
// SAFETY: read only and we only use Rx related flags
let sr = sr(r).read();
// This read also clears the error and idle interrupt flags on v1.
rdr(r).read_volatile();
clear_interrupt_flags(r, sr);
r.cr1().modify(|w| w.set_idleie(true));
sr
}
}
#[cfg(all(feature = "unstable-traits", feature = "nightly"))]
mod eio {