timer: clamp compare value before dma

Author: xoviat

embassy-stm32/src/dma/word.rs

@@ -31,6 +31,10 @@ pub trait Word: SealedWord + Default + Copy + 'static {
     fn size() -> WordSize;
     /// Amount of bits of this word size.
     fn bits() -> usize;
+    /// Maximum value of this type.
+    fn max() -> usize {
+        (1 << Self::bits()) - 1
+    }
 }
 
 macro_rules! impl_word {

embassy-stm32/src/timer/complementary_pwm.rs

@@ -228,7 +228,7 @@ impl<'d, T: AdvancedInstance4Channel> ComplementaryPwm<'d, T> {
         duty: &[W],
     ) {
         self.inner.enable_channel(channel, true);
-        self.inner.set_compare_value(channel, 0.into());
+        self.inner.clamp_compare_value::<W>(channel);
         self.inner.enable_update_dma(true);
         self.inner.setup_update_dma(dma, channel, duty).await;
         self.inner.enable_update_dma(false);
@@ -276,7 +276,7 @@ impl<'d, T: AdvancedInstance4Channel> ComplementaryPwm<'d, T> {
             .filter(|ch| ch.index() <= ending_channel.index())
             .for_each(|ch| {
                 self.inner.enable_channel(*ch, true);
-                self.inner.set_compare_value(*ch, 0.into());
+                self.inner.clamp_compare_value::<W>(*ch);
             });
         self.inner.enable_update_dma(true);
         self.inner

embassy-stm32/src/timer/low_level.rs

@@ -627,6 +627,18 @@ impl<'d, T: GeneralInstance4Channel> Timer<'d, T> {
         return unwrap!(self.regs_gp32_unchecked().ccr(channel.index()).read().ccr().try_into());
     }
 
+    pub(crate) fn clamp_compare_value<W: Word>(&mut self, channel: Channel) {
+        self.set_compare_value(
+            channel,
+            unwrap!(
+                self.get_compare_value(channel)
+                    .into()
+                    .clamp(0, W::max() as u32)
+                    .try_into()
+            ),
+        );
+    }
+
     /// Setup a ring buffer for the channel
     pub fn setup_ring_buffer<'a, W: Word + Into<T::Word>>(
         &mut self,

embassy-stm32/src/timer/simple_pwm.rs

@@ -179,6 +179,7 @@ impl<'d, T: GeneralInstance4Channel> SimplePwmChannel<'d, T> {
     ) -> RingBufferedPwmChannel<'d, T, W> {
         assert!(!dma_buf.is_empty() && dma_buf.len() <= 0xFFFF);
 
+        self.timer.clamp_compare_value::<W>(self.channel);
         self.timer.enable_update_dma(true);
 
         RingBufferedPwmChannel::new(
@@ -352,7 +353,7 @@ impl<'d, T: GeneralInstance4Channel> SimplePwm<'d, T> {
         duty: &[W],
     ) {
         self.inner.enable_channel(channel, true);
-        self.inner.set_compare_value(channel, 0.into());
+        self.inner.clamp_compare_value::<W>(channel);
         self.inner.enable_update_dma(true);
         self.inner.setup_update_dma(dma, channel, duty).await;
         self.inner.enable_update_dma(false);
@@ -400,7 +401,7 @@ impl<'d, T: GeneralInstance4Channel> SimplePwm<'d, T> {
             .filter(|ch| ch.index() <= ending_channel.index())
             .for_each(|ch| {
                 self.inner.enable_channel(*ch, true);
-                self.inner.set_compare_value(*ch, 0.into());
+                self.inner.clamp_compare_value::<W>(*ch);
             });
         self.inner.enable_update_dma(true);
         self.inner