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Changed busy wait to wfe #604

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Changed busy wait to wfe #604

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15 changes: 9 additions & 6 deletions rp2040-hal/src/sio.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -137,7 +137,13 @@ impl SioFifo {
pub fn read(&mut self) -> Option<u32> {
if self.is_read_ready() {
let sio = unsafe { &(*pac::SIO::ptr()) };
Some(sio.fifo_rd.read().bits())

let value = sio.fifo_rd.read().bits();

// Wake up the other core that might be waiting on a read
cortex_m::asm::sev();

Some(value)
} else {
None
}
Expand All @@ -152,17 +158,14 @@ impl SioFifo {

/// Push to the FIFO, spinning if there's no space.
pub fn write_blocking(&mut self, value: u32) {
// We busy-wait for the FIFO to have some space
// We wait for the FIFO to have some space
while !self.is_write_ready() {
cortex_m::asm::nop();
cortex_m::asm::wfe();
}

// Write the value to the FIFO - the other core will now be able to
// pop it off its end of the FIFO.
self.write(value);

// Fire off an event to the other core
cortex_m::asm::sev();
}

/// Pop from the FIFO, spinning if there's currently no data.
Expand Down