rp: Fix BufferedUart drop code

Only unregister the interrupt handler when both parts are inactive

embassy-hal-common/src/atomic_ring_buffer.rs

@@ -81,6 +81,10 @@ impl RingBuffer {
         Writer(self)
     }
 
+    pub fn len(&self) -> usize {
+        self.len.load(Ordering::Relaxed)
+    }
+
     pub fn is_full(&self) -> bool {
         let len = self.len.load(Ordering::Relaxed);
         let start = self.start.load(Ordering::Relaxed);

embassy-rp/src/uart/buffered.rs

@@ -27,7 +27,8 @@ impl State {
 }
 
 pub struct BufferedUart<'d, T: Instance> {
-    phantom: PhantomData<&'d mut T>,
+    rx: BufferedUartRx<'d, T>,
+    tx: BufferedUartTx<'d, T>,
 }
 
 pub struct BufferedUartRx<'d, T: Instance> {
@@ -91,7 +92,10 @@ impl<'d, T: Instance> BufferedUart<'d, T> {
             rx_buffer,
             config,
         );
-        Self { phantom: PhantomData }
+        Self {
+            rx: BufferedUartRx { phantom: PhantomData },
+            tx: BufferedUartTx { phantom: PhantomData },
+        }
     }
 
     pub fn new_with_rtscts(
@@ -116,14 +120,14 @@ impl<'d, T: Instance> BufferedUart<'d, T> {
             rx_buffer,
             config,
         );
-        Self { phantom: PhantomData }
+        Self {
+            rx: BufferedUartRx { phantom: PhantomData },
+            tx: BufferedUartTx { phantom: PhantomData },
+        }
     }
 
-    pub fn split(&mut self) -> (BufferedUartRx<'d, T>, BufferedUartTx<'d, T>) {
-        (
-            BufferedUartRx { phantom: PhantomData },
-            BufferedUartTx { phantom: PhantomData },
-        )
+    pub fn split(self) -> (BufferedUartRx<'d, T>, BufferedUartTx<'d, T>) {
+        (self.rx, self.tx)
     }
 }
 
@@ -269,35 +273,32 @@ impl<'d, T: Instance> BufferedUartTx<'d, T> {
     }
 }
 
-impl<'d, T: Instance> Drop for BufferedUart<'d, T> {
-    fn drop(&mut self) {
-        unsafe {
-            T::Interrupt::steal().disable();
-            let state = T::state();
-            state.tx_buf.deinit();
-            state.rx_buf.deinit();
-        }
-    }
-}
-
 impl<'d, T: Instance> Drop for BufferedUartRx<'d, T> {
     fn drop(&mut self) {
-        unsafe {
-            T::Interrupt::steal().disable();
         let state = T::state();
-            state.tx_buf.deinit();
+        unsafe {
             state.rx_buf.deinit();
+
+            // TX is inactive if the the buffer is not available.
+            // We can now unregister the interrupt handler
+            if state.tx_buf.len() == 0 {
+                T::Interrupt::steal().disable();
+            }
         }
     }
 }
 
 impl<'d, T: Instance> Drop for BufferedUartTx<'d, T> {
     fn drop(&mut self) {
-        unsafe {
-            T::Interrupt::steal().disable();
         let state = T::state();
+        unsafe {
             state.tx_buf.deinit();
-            state.rx_buf.deinit();
+
+            // RX is inactive if the the buffer is not available.
+            // We can now unregister the interrupt handler
+            if state.rx_buf.len() == 0 {
+                T::Interrupt::steal().disable();
+            }
         }
     }
 }

examples/rp/src/bin/uart_buffered_split.rs

@@ -29,7 +29,7 @@ async fn main(spawner: Spawner) {
     let irq = interrupt::take!(UART0_IRQ);
     let tx_buf = &mut singleton!([0u8; 16])[..];
     let rx_buf = &mut singleton!([0u8; 16])[..];
-    let mut uart = BufferedUart::new(uart, irq, tx_pin, rx_pin, tx_buf, rx_buf, Config::default());
+    let uart = BufferedUart::new(uart, irq, tx_pin, rx_pin, tx_buf, rx_buf, Config::default());
     let (rx, mut tx) = uart.split();
 
     unwrap!(spawner.spawn(reader(rx)));