Acquire semaphore on blocking
@@ -257,9 +257,19 @@ impl<'d, T: Instance> Spis<'d, T> {
}
fn blocking_inner_from_ram(&mut self, rx: *mut [u8], tx: *const [u8]) -> Result<(usize, usize), Error> {
- self.prepare(rx, tx)?;
+ compiler_fence(Ordering::SeqCst);
let r = T::regs();
+ // Acquire semaphore.
+ if r.semstat.read().bits() != 1 {
+ r.events_acquired.reset();
+ r.tasks_acquire.write(|w| unsafe { w.bits(1) });
+ // Wait until CPU has acquired the semaphore.
+ while r.semstat.read().bits() != 1 {}
+ }
+
+ self.prepare(rx, tx)?;
+
// Wait for 'end' event.
while r.events_end.read().bits() == 0 {}
@@ -291,6 +301,7 @@ impl<'d, T: Instance> Spis<'d, T> {
// Clear status register.
r.status.write(|w| w.overflow().clear().overread().clear());
+ // Acquire semaphore.
if r.semstat.read().bits() != 1 {
// Reset and enable the acquire event.
r.events_acquired.reset();
@@ -299,10 +310,10 @@ impl<'d, T: Instance> Spis<'d, T> {
// Request acquiring the SPIS semaphore.
r.tasks_acquire.write(|w| unsafe { w.bits(1) });
- // Wait for 'acquire' event.
+ // Wait until CPU has acquired the semaphore.
poll_fn(|cx| {
s.acquire_waker.register(cx.waker());
- if r.events_acquired.read().bits() != 0 {
+ if r.semstat.read().bits() == 1 {
return Poll::Ready(());
}
Poll::Pending
