hal/src/dprintf_hal.rs

//! Unsafe synchronous dump-string-to-uart impl and macro for debugging.

use core2::io::{Cursor, Write};
use core::fmt;

// TODO(jtgans|aappleby): b/239714445. Use the actual UART registers defined in
// opentitan/uart.rs instead of hardcoding them here. Or better: get rid of this
// gross hack and replace with something less gross. :P
pub const TX_BUSY: *const u32 = 0x4000_0014 as *const u32;
pub const TX_PORT: *mut u32 = 0x4000_001c as *mut u32;

pub fn send_sync(buf: &[u8], len: usize) {
    unsafe {
        for i in 0..len {
            // TODO(jtgans|aappleby): b/239714445. This is a gross hack to
            // ensure we don't buffer dprintf output for diagnosing early boot
            // of the system.
            //
            // NOTE: if the UART registers change, we're going to have to fix
            // this here as well!
            while (TX_BUSY.read_volatile() & 1) != 0 {}
            TX_PORT.write_volatile(buf[i] as u32);
        }
    }
}

pub fn vdprintf(args: fmt::Arguments) {
    let mut uart_buf = [0u8; 256];
    let mut cur = Cursor::new(&mut uart_buf[..]);
    if cur.write_fmt(args).is_ok() {
        let pos = cur.position();
        send_sync(&uart_buf, pos as usize);
    }
}

#[macro_export]
macro_rules! dprintf {
    ($msg:expr) => ({
        $crate::dprintf_hal::vdprintf(format_args!($msg))
    });
    ($fmt:expr, $($arg:tt)+) => ({
        $crate::dprintf_hal::vdprintf(format_args!($fmt, $($arg)+))
    });
}