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|
//! Data Watchpoint Trace (DWT) unit's CYCle CouNTer
use core::{
cmp::Ordering,
convert::{Infallible, TryInto},
fmt,
marker::PhantomData,
ops,
};
use cortex_m::peripheral::DWT;
use crate::Fraction;
/// A measurement of the CYCCNT. Opaque and useful only with `Duration`
///
/// This data type is only available on ARMv7-M
///
/// Note that this value is tied to the CYCCNT of one core and that sending it a different core
/// makes it lose its meaning -- each Cortex-M core has its own CYCCNT counter and these are usually
/// unsynchronized and they may even be running at different frequencies.
#[derive(Clone, Copy, Eq, PartialEq)]
pub struct Instant {
inner: i32,
_not_send_or_sync: PhantomData<*mut ()>,
}
unsafe impl Sync for Instant {}
unsafe impl Send for Instant {}
impl Instant {
/// Returns an instant corresponding to "now"
pub fn now() -> Self {
Instant {
inner: DWT::get_cycle_count() as i32,
_not_send_or_sync: PhantomData,
}
}
/// Returns the amount of time elapsed since this instant was created.
pub fn elapsed(&self) -> Duration {
Instant::now() - *self
}
/// Returns the amount of time elapsed from another instant to this one.
pub fn duration_since(&self, earlier: Instant) -> Duration {
let diff = self.inner - earlier.inner;
assert!(diff >= 0, "second instant is later than self");
Duration { inner: diff as u32 }
}
}
impl fmt::Debug for Instant {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_tuple("Instant")
.field(&(self.inner as u32))
.finish()
}
}
impl ops::AddAssign<Duration> for Instant {
fn add_assign(&mut self, dur: Duration) {
debug_assert!(dur.inner < (1 << 31));
self.inner = self.inner.wrapping_add(dur.inner as i32);
}
}
impl ops::Add<Duration> for Instant {
type Output = Self;
fn add(mut self, dur: Duration) -> Self {
self += dur;
self
}
}
impl ops::SubAssign<Duration> for Instant {
fn sub_assign(&mut self, dur: Duration) {
// XXX should this be a non-debug assertion?
debug_assert!(dur.inner < (1 << 31));
self.inner = self.inner.wrapping_sub(dur.inner as i32);
}
}
impl ops::Sub<Duration> for Instant {
type Output = Self;
fn sub(mut self, dur: Duration) -> Self {
self -= dur;
self
}
}
impl ops::Sub<Instant> for Instant {
type Output = Duration;
fn sub(self, other: Instant) -> Duration {
self.duration_since(other)
}
}
impl Ord for Instant {
fn cmp(&self, rhs: &Self) -> Ordering {
self.inner.wrapping_sub(rhs.inner).cmp(&0)
}
}
impl PartialOrd for Instant {
fn partial_cmp(&self, rhs: &Self) -> Option<Ordering> {
Some(self.cmp(rhs))
}
}
/// A `Duration` type to represent a span of time.
///
/// This data type is only available on ARMv7-M
#[derive(Clone, Copy, Default, Eq, Ord, PartialEq, PartialOrd)]
pub struct Duration {
inner: u32,
}
impl Duration {
/// Creates a new `Duration` from the specified number of clock cycles
pub fn from_cycles(cycles: u32) -> Self {
Duration { inner: cycles }
}
/// Returns the total number of clock cycles contained by this `Duration`
pub fn as_cycles(&self) -> u32 {
self.inner
}
}
impl TryInto<u32> for Duration {
type Error = Infallible;
fn try_into(self) -> Result<u32, Infallible> {
Ok(self.as_cycles())
}
}
impl ops::AddAssign for Duration {
fn add_assign(&mut self, dur: Duration) {
self.inner += dur.inner;
}
}
impl ops::Add<Duration> for Duration {
type Output = Self;
fn add(self, other: Self) -> Self {
Duration {
inner: self.inner + other.inner,
}
}
}
impl ops::SubAssign for Duration {
fn sub_assign(&mut self, rhs: Duration) {
self.inner -= rhs.inner;
}
}
impl ops::Sub<Duration> for Duration {
type Output = Self;
fn sub(self, rhs: Self) -> Self {
Duration {
inner: self.inner - rhs.inner,
}
}
}
/// Adds the `cycles` method to the `u32` type
///
/// This trait is only available on ARMv7-M
pub trait U32Ext {
/// Converts the `u32` value into clock cycles
fn cycles(self) -> Duration;
}
impl U32Ext for u32 {
fn cycles(self) -> Duration {
Duration { inner: self }
}
}
/// Implementation of the `Monotonic` trait based on CYCle CouNTer
pub struct CYCCNT;
impl crate::Monotonic for CYCCNT {
type Instant = Instant;
fn ratio() -> Fraction {
Fraction {
numerator: 1,
denominator: 1,
}
}
unsafe fn reset() {
(0xE0001004 as *mut u32).write_volatile(0)
}
fn now() -> Instant {
Instant::now()
}
fn zero() -> Instant {
Instant {
inner: 0,
_not_send_or_sync: PhantomData,
}
}
}
|
