1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158
//! Instrumentation Trace Macrocell
//!
//! **NOTE** This module is only available on ARMv7-M and newer.
use core::{fmt, ptr, slice};
use crate::peripheral::itm::Stim;
// NOTE assumes that `bytes` is 32-bit aligned
unsafe fn write_words(stim: &mut Stim, bytes: &[u32]) {
let mut p = bytes.as_ptr();
for _ in 0..bytes.len() {
while !stim.is_fifo_ready() {}
stim.write_u32(ptr::read(p));
p = p.offset(1);
}
}
/// Writes an aligned byte slice to the ITM.
///
/// `buffer` must be 4-byte aligned.
unsafe fn write_aligned_impl(port: &mut Stim, buffer: &[u8]) {
let len = buffer.len();
if len == 0 {
return;
}
let split = len & !0b11;
#[allow(clippy::cast_ptr_alignment)]
write_words(
port,
slice::from_raw_parts(buffer.as_ptr() as *const u32, split >> 2),
);
// 3 bytes or less left
let mut left = len & 0b11;
let mut ptr = buffer.as_ptr().add(split);
// at least 2 bytes left
if left > 1 {
while !port.is_fifo_ready() {}
#[allow(clippy::cast_ptr_alignment)]
port.write_u16(ptr::read(ptr as *const u16));
ptr = ptr.offset(2);
left -= 2;
}
// final byte
if left == 1 {
while !port.is_fifo_ready() {}
port.write_u8(*ptr);
}
}
struct Port<'p>(&'p mut Stim);
impl<'p> fmt::Write for Port<'p> {
#[inline]
fn write_str(&mut self, s: &str) -> fmt::Result {
write_all(self.0, s.as_bytes());
Ok(())
}
}
/// A wrapper type that aligns its contents on a 4-Byte boundary.
///
/// ITM transfers are most efficient when the data is 4-Byte-aligned. This type provides an easy
/// way to accomplish and enforce such an alignment.
#[repr(align(4))]
pub struct Aligned<T: ?Sized>(pub T);
/// Writes `buffer` to an ITM port.
#[allow(clippy::missing_inline_in_public_items)]
pub fn write_all(port: &mut Stim, buffer: &[u8]) {
unsafe {
let mut len = buffer.len();
let mut ptr = buffer.as_ptr();
if len == 0 {
return;
}
// 0x01 OR 0x03
if ptr as usize % 2 == 1 {
while !port.is_fifo_ready() {}
port.write_u8(*ptr);
// 0x02 OR 0x04
ptr = ptr.offset(1);
len -= 1;
}
// 0x02
if ptr as usize % 4 == 2 {
if len > 1 {
// at least 2 bytes
while !port.is_fifo_ready() {}
// We checked the alignment above, so this is safe
#[allow(clippy::cast_ptr_alignment)]
port.write_u16(ptr::read(ptr as *const u16));
// 0x04
ptr = ptr.offset(2);
len -= 2;
} else {
if len == 1 {
// last byte
while !port.is_fifo_ready() {}
port.write_u8(*ptr);
}
return;
}
}
// The remaining data is 4-byte aligned, but might not be a multiple of 4 bytes
write_aligned_impl(port, slice::from_raw_parts(ptr, len));
}
}
/// Writes a 4-byte aligned `buffer` to an ITM port.
///
/// # Examples
///
/// ```no_run
/// # use cortex_m::{itm::{self, Aligned}, peripheral::ITM};
/// # let port = unsafe { &mut (*ITM::PTR).stim[0] };
/// let mut buffer = Aligned([0; 14]);
///
/// buffer.0.copy_from_slice(b"Hello, world!\n");
///
/// itm::write_aligned(port, &buffer);
///
/// // Or equivalently
/// itm::write_aligned(port, &Aligned(*b"Hello, world!\n"));
/// ```
#[allow(clippy::missing_inline_in_public_items)]
pub fn write_aligned(port: &mut Stim, buffer: &Aligned<[u8]>) {
unsafe { write_aligned_impl(port, &buffer.0) }
}
/// Writes `fmt::Arguments` to the ITM `port`
#[inline]
pub fn write_fmt(port: &mut Stim, args: fmt::Arguments) {
use core::fmt::Write;
Port(port).write_fmt(args).ok();
}
/// Writes a string to the ITM `port`
#[inline]
pub fn write_str(port: &mut Stim, string: &str) {
write_all(port, string.as_bytes())
}