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stm32 usart: Fix RX interrupt flag handling

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* On v1 interrupts cannot be cleared individually.
  Instead they are cleared implicitly by reading or writing DR (which we do now).
* Multiple error flags can be set at the same time:
  Handle them all in one go intstead of re-entering the ISR for each one so that
  we do not lose any error flags on v1 hardware.
* Wake when the RX buffer becomes full: This allows fast running chips to pull data
  from the buffer before receiving the next byte.
This commit is contained in:
Timo Kröger
2022-02-25 13:19:51 +01:00
parent 6da4b66364
commit 48f700b35c
1 changed files with 36 additions and 58 deletions
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94
embassy-stm32/src/usart/mod.rs
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@@ -395,29 +395,39 @@ mod buffered {
let r = self.uart.inner.regs();
unsafe {
let sr = sr(r).read();
// TODO: do we want to handle interrupts the same way on v1 hardware?
if sr.pe() {
clear_interrupt_flag(r, InterruptFlag::PE);
trace!("Parity error");
} else if sr.fe() {
clear_interrupt_flag(r, InterruptFlag::FE);
trace!("Framing error");
} else if sr.ne() {
clear_interrupt_flag(r, InterruptFlag::NE);
trace!("Noise error");
} else if sr.ore() {
clear_interrupt_flag(r, InterruptFlag::ORE);
trace!("Overrun error");
} else if sr.rxne() {
let buf = self.rx.push_buf();
if buf.is_empty() {
self.rx_waker.wake();
} else {
buf[0] = rdr(r).read_volatile();
self.rx.push(1);
clear_interrupt_flags(r, sr);
// This read also clears the error and idle interrupt flags on v1.
let b = rdr(r).read_volatile();
if sr.rxne() {
if sr.pe() {
warn!("Parity error");
}
} else if sr.idle() {
clear_interrupt_flag(r, InterruptFlag::IDLE);
if sr.fe() {
warn!("Framing error");
}
if sr.ne() {
warn!("Noise error");
}
if sr.ore() {
warn!("Overrun error");
}
let buf = self.rx.push_buf();
if !buf.is_empty() {
buf[0] = b;
self.rx.push(1);
} else {
warn!("RX buffer full, discard received byte");
}
if self.rx.is_full() {
self.rx_waker.wake();
}
}
if sr.idle() {
self.rx_waker.wake();
};
}
@@ -542,28 +552,14 @@ fn rdr(r: crate::pac::usart::Usart) -> *mut u8 {
r.dr().ptr() as _
}
enum InterruptFlag {
PE,
FE,
NE,
ORE,
IDLE,
}
#[cfg(usart_v1)]
fn sr(r: crate::pac::usart::Usart) -> crate::pac::common::Reg<regs::Sr, crate::pac::common::RW> {
r.sr()
}
#[cfg(usart_v1)]
unsafe fn clear_interrupt_flag(r: crate::pac::usart::Usart, _flag: InterruptFlag) {
// This bit is set by hardware when noise is detected on a received frame. It is cleared by a
// software sequence (an read to the USART_SR register followed by a read to the
// USART_DR register).
// this is the same as what st's HAL does on v1 hardware
r.sr().read();
r.dr().read();
unsafe fn clear_interrupt_flags(_r: crate::pac::usart::Usart, _sr: regs::Sr) {
// On v1 the flags are cleared implicitly by reads and writes to DR.
}
#[cfg(usart_v2)]
@@ -582,26 +578,8 @@ fn sr(r: crate::pac::usart::Usart) -> crate::pac::common::Reg<regs::Ixr, crate::
}
#[cfg(usart_v2)]
#[inline]
unsafe fn clear_interrupt_flag(r: crate::pac::usart::Usart, flag: InterruptFlag) {
// v2 has a separate register for clearing flags (nice)
match flag {
InterruptFlag::PE => r.icr().write(|w| {
w.set_pe(true);
}),
InterruptFlag::FE => r.icr().write(|w| {
w.set_fe(true);
}),
InterruptFlag::NE => r.icr().write(|w| {
w.set_ne(true);
}),
InterruptFlag::ORE => r.icr().write(|w| {
w.set_ore(true);
}),
InterruptFlag::IDLE => r.icr().write(|w| {
w.set_idle(true);
}),
}
unsafe fn clear_interrupt_flags(r: crate::pac::usart::Usart, sr: regs::Ixr) {
r.icr().write(|w| *w = sr);
}
pub(crate) mod sealed {