7 files changed, 98 insertions, 5 deletions

diff --git a/embassy-stm32/build.rs b/embassy-stm32/build.rs
index 6c364f7bb..aef0668a2 100644
--- a/embassy-stm32/build.rs
+++ b/embassy-stm32/build.rs
@@ -308,6 +308,10 @@ fn main() {
     // ========
     // Generate RccPeripheral impls
 
+    // TODO: maybe get this from peripheral kind? Not sure
+    let refcounted_peripherals = HashSet::from(["USART"]);
+    let mut refcount_statics = HashSet::new();
+
     for p in METADATA.peripherals {
         // generating RccPeripheral impl for H7 ADC3 would result in bad frequency
         if !singletons.contains(&p.name.to_string())
@@ -344,11 +348,36 @@ fn main() {
                 TokenStream::new()
             };
 
+            let ptype = (if let Some(reg) = &p.registers { reg.kind } else { "" }).to_ascii_uppercase();
             let pname = format_ident!("{}", p.name);
             let clk = format_ident!("{}", rcc.clock.to_ascii_lowercase());
             let en_reg = format_ident!("{}", en.register.to_ascii_lowercase());
             let set_en_field = format_ident!("set_{}", en.field.to_ascii_lowercase());
 
+            let (before_enable, before_disable) = if refcounted_peripherals.contains(ptype.as_str()) {
+                let refcount_static =
+                    format_ident!("{}_{}", en.register.to_ascii_uppercase(), en.field.to_ascii_uppercase());
+
+                refcount_statics.insert(refcount_static.clone());
+
+                (
+                    quote! {
+                        unsafe { refcount_statics::#refcount_static += 1 };
+                        if unsafe { refcount_statics::#refcount_static } > 1 {
+                            return;
+                        }
+                    },
+                    quote! {
+                        unsafe { refcount_statics::#refcount_static -= 1 };
+                        if unsafe { refcount_statics::#refcount_static } > 0  {
+                            return;
+                        }
+                    },
+                )
+            } else {
+                (TokenStream::new(), TokenStream::new())
+            };
+
             g.extend(quote! {
                 impl crate::rcc::sealed::RccPeripheral for peripherals::#pname {
                     fn frequency() -> crate::time::Hertz {
@@ -356,6 +385,7 @@ fn main() {
                     }
                     fn enable() {
                         critical_section::with(|_| {
+                            #before_enable
                             #[cfg(feature = "low-power")]
                             crate::rcc::clock_refcount_add();
                             crate::pac::RCC.#en_reg().modify(|w| w.#set_en_field(true));
@@ -364,6 +394,7 @@ fn main() {
                     }
                     fn disable() {
                         critical_section::with(|_| {
+                            #before_disable
                             crate::pac::RCC.#en_reg().modify(|w| w.#set_en_field(false));
                             #[cfg(feature = "low-power")]
                             crate::rcc::clock_refcount_sub();
@@ -379,6 +410,19 @@ fn main() {
         }
     }
 
+    let mut refcount_mod = TokenStream::new();
+    for refcount_static in refcount_statics {
+        refcount_mod.extend(quote! {
+            pub(crate) static mut #refcount_static: u8 = 0;
+        });
+    }
+
+    g.extend(quote! {
+        mod refcount_statics {
+            #refcount_mod
+        }
+    });
+
     // ========
     // Generate fns to enable GPIO, DMA in RCC
 
diff --git a/embassy-stm32/src/i2c/v1.rs b/embassy-stm32/src/i2c/v1.rs
index 618d85af2..f32dd0f0c 100644
--- a/embassy-stm32/src/i2c/v1.rs
+++ b/embassy-stm32/src/i2c/v1.rs
@@ -339,6 +339,12 @@ impl<'d, T: Instance, TXDMA, RXDMA> I2c<'d, T, TXDMA, RXDMA> {
     }
 }
 
+impl<'d, T: Instance, TXDMA, RXDMA> Drop for I2c<'d, T, TXDMA, RXDMA> {
+    fn drop(&mut self) {
+        T::disable();
+    }
+}
+
 impl<'d, T: Instance> embedded_hal_02::blocking::i2c::Read for I2c<'d, T> {
     type Error = Error;
 
diff --git a/embassy-stm32/src/i2c/v2.rs b/embassy-stm32/src/i2c/v2.rs
index 4327899bb..36f70e32e 100644
--- a/embassy-stm32/src/i2c/v2.rs
+++ b/embassy-stm32/src/i2c/v2.rs
@@ -838,6 +838,12 @@ impl<'d, T: Instance, TXDMA, RXDMA> I2c<'d, T, TXDMA, RXDMA> {
     }
 }
 
+impl<'d, T: Instance, TXDMA, RXDMA> Drop for I2c<'d, T, TXDMA, RXDMA> {
+    fn drop(&mut self) {
+        T::disable();
+    }
+}
+
 mod eh02 {
     use super::*;
 
diff --git a/embassy-stm32/src/spi/mod.rs b/embassy-stm32/src/spi/mod.rs
index e2bc8d7f2..853de98f9 100644
--- a/embassy-stm32/src/spi/mod.rs
+++ b/embassy-stm32/src/spi/mod.rs
@@ -646,6 +646,8 @@ impl<'d, T: Instance, Tx, Rx> Drop for Spi<'d, T, Tx, Rx> {
         self.sck.as_ref().map(|x| x.set_as_disconnected());
         self.mosi.as_ref().map(|x| x.set_as_disconnected());
         self.miso.as_ref().map(|x| x.set_as_disconnected());
+
+        T::disable();
     }
 }
 
diff --git a/embassy-stm32/src/usart/buffered.rs b/embassy-stm32/src/usart/buffered.rs
index 596d40bf9..989c88205 100644
--- a/embassy-stm32/src/usart/buffered.rs
+++ b/embassy-stm32/src/usart/buffered.rs
@@ -124,6 +124,8 @@ impl<'d, T: BasicInstance> BufferedUart<'d, T> {
         rx_buffer: &'d mut [u8],
         config: Config,
     ) -> BufferedUart<'d, T> {
+        // UartRx and UartTx have one refcount ea.
+        T::enable();
         T::enable();
         T::reset();
 
@@ -143,6 +145,8 @@ impl<'d, T: BasicInstance> BufferedUart<'d, T> {
     ) -> BufferedUart<'d, T> {
         into_ref!(cts, rts);
 
+        // UartRx and UartTx have one refcount ea.
+        T::enable();
         T::enable();
         T::reset();
 
@@ -169,6 +173,8 @@ impl<'d, T: BasicInstance> BufferedUart<'d, T> {
     ) -> BufferedUart<'d, T> {
         into_ref!(de);
 
+        // UartRx and UartTx have one refcount ea.
+        T::enable();
         T::enable();
         T::reset();
 
@@ -382,6 +388,8 @@ impl<'d, T: BasicInstance> Drop for BufferedUartRx<'d, T> {
                 T::Interrupt::disable();
             }
         }
+
+        T::disable();
     }
 }
 
@@ -397,6 +405,8 @@ impl<'d, T: BasicInstance> Drop for BufferedUartTx<'d, T> {
                 T::Interrupt::disable();
             }
         }
+
+        T::disable();
     }
 }
 
diff --git a/embassy-stm32/src/usart/mod.rs b/embassy-stm32/src/usart/mod.rs
index 255ddfd4b..bfb056718 100644
--- a/embassy-stm32/src/usart/mod.rs
+++ b/embassy-stm32/src/usart/mod.rs
@@ -618,6 +618,18 @@ impl<'d, T: BasicInstance, RxDma> UartRx<'d, T, RxDma> {
     }
 }
 
+impl<'d, T: BasicInstance, TxDma> Drop for UartTx<'d, T, TxDma> {
+    fn drop(&mut self) {
+        T::disable();
+    }
+}
+
+impl<'d, T: BasicInstance, TxDma> Drop for UartRx<'d, T, TxDma> {
+    fn drop(&mut self) {
+        T::disable();
+    }
+}
+
 impl<'d, T: BasicInstance, TxDma, RxDma> Uart<'d, T, TxDma, RxDma> {
     pub fn new(
         peri: impl Peripheral<P = T> + 'd,
@@ -628,6 +640,8 @@ impl<'d, T: BasicInstance, TxDma, RxDma> Uart<'d, T, TxDma, RxDma> {
         rx_dma: impl Peripheral<P = RxDma> + 'd,
         config: Config,
     ) -> Self {
+        // UartRx and UartTx have one refcount ea.
+        T::enable();
         T::enable();
         T::reset();
 
@@ -647,6 +661,8 @@ impl<'d, T: BasicInstance, TxDma, RxDma> Uart<'d, T, TxDma, RxDma> {
     ) -> Self {
         into_ref!(cts, rts);
 
+        // UartRx and UartTx have one refcount ea.
+        T::enable();
         T::enable();
         T::reset();
 
@@ -672,6 +688,8 @@ impl<'d, T: BasicInstance, TxDma, RxDma> Uart<'d, T, TxDma, RxDma> {
     ) -> Self {
         into_ref!(de);
 
+        // UartRx and UartTx have one refcount ea.
+        T::enable();
         T::enable();
         T::reset();
 
diff --git a/embassy-stm32/src/usart/ringbuffered.rs b/embassy-stm32/src/usart/ringbuffered.rs
index b3f570624..e990eaca8 100644
--- a/embassy-stm32/src/usart/ringbuffered.rs
+++ b/embassy-stm32/src/usart/ringbuffered.rs
@@ -1,4 +1,5 @@
 use core::future::poll_fn;
+use core::mem;
 use core::sync::atomic::{compiler_fence, Ordering};
 use core::task::Poll;
 
@@ -24,12 +25,16 @@ 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 { ReadableRingBuffer::new_read(self.rx_dma, request, rdr(T::regs()), dma_buf, opts) };
+        // Safety: we forget the struct before this function returns.
+        let rx_dma = unsafe { self.rx_dma.clone_unchecked() };
+        let _peri = unsafe { self._peri.clone_unchecked() };
 
-        RingBufferedUartRx {
-            _peri: self._peri,
-            ring_buf,
-        }
+        let ring_buf = unsafe { ReadableRingBuffer::new_read(rx_dma, request, rdr(T::regs()), dma_buf, opts) };
+
+        // Don't disable the clock
+        mem::forget(self);
+
+        RingBufferedUartRx { _peri, ring_buf }
     }
 }
 
@@ -186,6 +191,8 @@ impl<'d, T: BasicInstance, RxDma: super::RxDma<T>> RingBufferedUartRx<'d, T, RxD
 impl<T: BasicInstance, RxDma: super::RxDma<T>> Drop for RingBufferedUartRx<'_, T, RxDma> {
     fn drop(&mut self) {
         self.teardown_uart();
+
+        T::disable();
     }
 }
 /// Return an error result if the Sr register has errors