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78 lines
2.1 KiB
Rust
78 lines
2.1 KiB
Rust
// SPDX-License-Identifier: MIT
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//
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// Copyright (c) 2018-2019 Andre Richter <andre.o.richter@gmail.com>
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//! Timer primitives.
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use crate::{interface, warn};
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use core::time::Duration;
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use cortex_a::regs::*;
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const NS_PER_S: u64 = 1_000_000_000;
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pub struct Timer;
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impl interface::time::Timer for Timer {
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fn resoultion(&self) -> Duration {
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Duration::from_nanos(NS_PER_S / (CNTFRQ_EL0.get() as u64))
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}
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fn uptime(&self) -> Duration {
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let frq: u64 = CNTFRQ_EL0.get() as u64;
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let current_count: u64 = CNTPCT_EL0.get() * NS_PER_S;
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Duration::from_nanos(current_count / frq)
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}
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fn spin_for(&self, duration: Duration) {
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// Instantly return on zero.
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if duration.as_nanos() == 0 {
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return;
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}
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// Calculate the register compare value.
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let frq = CNTFRQ_EL0.get() as u64;
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let x = match frq.checked_mul(duration.as_nanos() as u64) {
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None => {
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warn!("Spin duration too long, skipping");
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return;
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}
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Some(val) => val,
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};
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let tval = x / NS_PER_S;
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// Check if it is within supported bounds.
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let warn: Option<&str> = if tval == 0 {
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Some("smaller")
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} else if tval > u32::max_value().into() {
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Some("bigger")
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} else {
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None
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};
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if let Some(w) = warn {
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warn!(
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"Spin duration {} than architecturally supported, skipping",
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w
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);
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return;
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}
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// Set the compare value register.
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CNTP_TVAL_EL0.set(tval as u32);
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// Kick off the counting. // Disable timer interrupt.
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CNTP_CTL_EL0.modify(CNTP_CTL_EL0::ENABLE::SET + CNTP_CTL_EL0::IMASK::SET);
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loop {
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// ISTATUS will be '1' when cval ticks have passed. Busy-check it.
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if CNTP_CTL_EL0.is_set(CNTP_CTL_EL0::ISTATUS) {
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break;
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}
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}
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// Disable counting again.
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CNTP_CTL_EL0.modify(CNTP_CTL_EL0::ENABLE::CLEAR);
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}
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}
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