riscv/riscv-peripheral/src/hal_async/aclint.rs

//! Asynchronous delay implementation for the (A)CLINT peripheral.

use crate::aclint::mtimer::MTIME;
pub use crate::hal::aclint::Delay;
pub use crate::hal_async::delay::DelayUs;
use core::{
    future::Future,
    pin::Pin,
    task::{Context, Poll},
};

struct DelayAsync {
    mtime: MTIME,
    t0: u64,
    n_ticks: u64,
}

impl DelayAsync {
    pub fn new(mtime: MTIME, n_ticks: u64) -> Self {
        let t0 = mtime.read();
        Self { mtime, t0, n_ticks }
    }
}

impl Future for DelayAsync {
    type Output = ();

    #[inline]
    fn poll(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Self::Output> {
        match self.mtime.read().wrapping_sub(self.t0) < self.n_ticks {
            true => Poll::Pending,
            false => Poll::Ready(()),
        }
    }
}

impl DelayUs for Delay {
    #[inline]
    async fn delay_us(&mut self, us: u32) {
        let n_ticks = us as u64 * self.get_freq() as u64 / 1_000_000;
        DelayAsync::new(self.get_mtime(), n_ticks).await;
    }

    #[inline]
    async fn delay_ms(&mut self, ms: u32) {
        let n_ticks = ms as u64 * self.get_freq() as u64 / 1_000;
        DelayAsync::new(self.get_mtime(), n_ticks).await;
    }
}