Add time management
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//! Modules specific to the aarch64 architecture.
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pub mod time;
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//! The implementation of the time management trait for aarch64.
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use core::arch::asm;
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use core::time::Duration;
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use crate::traits::time::TimeManager;
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use crate::println;
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const NS_PER_S: u64 = 1_000_000_000;
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const CNTP_CTL_EL0_ENABLE_MASK: u64 = 0b001;
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const CNTP_CTL_EL0_IMASK_MASK: u64 = 0b010;
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const CNTP_CTL_EL0_ISTATUS_MASK: u64 = 0b100;
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/// AARCH64 Timer.
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struct Timer;
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/// The global timer.
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static TIME_MANAGER: Timer = Timer;
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/// Return a reference to the global time manager.
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pub fn time_manager() -> &'static impl TimeManager {
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&TIME_MANAGER
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}
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impl TimeManager for Timer {
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fn frequency(&self) -> u64 {
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let freq: u64;
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unsafe {
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asm!("mrs {0:x}, CNTFRQ_EL0", out(reg) freq, options(nomem, nostack));
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}
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freq
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}
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fn uptime(&self) -> Duration {
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let ticks: u64;
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unsafe {
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// Protect against out of order execution
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// https://developer.arm.com/documentation/dui0802/b/CIHGHHIE
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// In effect this flush the processor pipeline
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asm!("ISB", options(nostack));
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asm!("mrs {0:x}, CNTPCT_EL0", out(reg) ticks, options(nomem, nostack));
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}
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Duration::from_nanos((ticks*NS_PER_S)/self.frequency())
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}
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fn sleep(&self, duration: Duration) {
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if duration.as_nanos() == 0 {
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return;
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}
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let tmp = match self.frequency().checked_mul(duration.as_nanos() as u64) {
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None => {
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println!("Cannot sleep this long, skipping");
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return;
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}
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Some(tmp) => tmp,
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};
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let ticks = tmp / NS_PER_S;
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if ticks > u32::max_value().into() {
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println!("Cannot wait more than 2^32-1 ticks on aarch64, skipping");
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return;
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}
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if ticks == 0 {
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println!("Duration is smaller than a clock tick, skipping.");
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return;
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}
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// Enable the timer and mask (disable) the interrupt
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let mut ctl: u64 = CNTP_CTL_EL0_ENABLE_MASK + CNTP_CTL_EL0_IMASK_MASK;
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unsafe {
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// set the register values for the timer
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asm!("msr CNTP_TVAL_EL0, {0:x}", in(reg) ticks, options(nomem, nostack));
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asm!("msr CNTP_CTL_EL0, {0:x}", in(reg) ctl, options(nomem, nostack));
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}
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// Loop waiting for the timer to run out
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while (ctl & CNTP_CTL_EL0_ISTATUS_MASK) == 0 {
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unsafe {
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asm!("mrs {0:x}, CNTP_CTL_EL0", out(reg) ctl, options(nomem, nostack));
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}
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}
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// Disable the counter
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ctl &= !CNTP_CTL_EL0_ENABLE_MASK;
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unsafe {
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asm!("msr CNTP_CTL_EL0, {0:x}", in(reg) ctl, options(nomem, nostack));
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}
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}
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}
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//! Traits for time management primitives.
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use core::time::Duration;
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pub trait TimeManager {
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/// Return the clock frequency, meaning the resolution of the
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/// time mesurement.
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fn frequency(&self) -> u64;
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/// The uptime since last power-on.
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fn uptime(&self) -> Duration;
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/// Sleep for the duration.
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fn sleep(&self, duration: Duration);
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}
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