Merge #429 #431

429: nrf/uarte: do not use WFE on drop. r=Dirbaio a=Dirbaio

- It disturbs other stuff that uses WFE/SEV in the system. I ran into issues with this.
- It needs the irq handler to check for RXTO/TXSTOPPED errors, which makes it slower.

431: interrupt: transmute instead of steal. r=Dirbaio a=Dirbaio

That steal method has a TAKEN=true write [here](6b013138b7/src/peripheral/mod.rs (L180)).
This is not zero cost, we don't want it. Transmute instead, which is zero cost.

Co-authored-by: Dario Nieuwenhuis <dirbaio@dirbaio.net>

embassy-nrf/src/uarte.rs

@@ -187,13 +187,6 @@ impl<'d, T: Instance> Uarte<'d, T> {
             s.endtx_waker.wake();
             r.intenclr.write(|w| w.endtx().clear());
         }
-
-        if r.events_rxto.read().bits() != 0 {
-            r.intenclr.write(|w| w.rxto().clear());
-        }
-        if r.events_txstopped.read().bits() != 0 {
-            r.intenclr.write(|w| w.txstopped().clear());
-        }
     }
 }
 
@@ -208,15 +201,9 @@ impl<'a, T: Instance> Drop for Uarte<'a, T> {
         info!("did_stoprx {} did_stoptx {}", did_stoprx, did_stoptx);
 
         // Wait for rxto or txstopped, if needed.
-        r.intenset.write(|w| w.rxto().set().txstopped().set());
         while (did_stoprx && r.events_rxto.read().bits() == 0)
             || (did_stoptx && r.events_txstopped.read().bits() == 0)
-        {
-            info!("uarte drop: wfe");
-            cortex_m::asm::wfe();
-        }
-
-        cortex_m::asm::sev();
+        {}
 
         // Finally we can disable!
         r.enable.write(|w| w.enable().disabled());

embassy/src/interrupt.rs

@@ -1,8 +1,8 @@
+use atomic_polyfill::{compiler_fence, AtomicPtr, Ordering};
+use core::mem;
 use core::ptr;
 use cortex_m::peripheral::NVIC;
 
-use atomic_polyfill::{compiler_fence, AtomicPtr, Ordering};
-
 pub use embassy_macros::interrupt_declare as declare;
 pub use embassy_macros::interrupt_take as take;
 
@@ -124,9 +124,8 @@ impl<T: Interrupt + ?Sized> InterruptExt for T {
     #[inline]
     fn set_priority(&self, prio: Self::Priority) {
         unsafe {
-            cortex_m::peripheral::Peripherals::steal()
-                .NVIC
-                .set_priority(NrWrap(self.number()), prio.into())
+            let mut nvic: cortex_m::peripheral::NVIC = mem::transmute(());
+            nvic.set_priority(NrWrap(self.number()), prio.into())
         }
     }
 }