43 lines
1.4 KiB
Rust
43 lines
1.4 KiB
Rust
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use crate::{
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interrupts::{self, EoiGuard},
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println, TASKING,
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};
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use spin::Mutex;
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use x86_64::instructions::port::{Port, PortWriteOnly};
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static DATA: Mutex<Port<u8>> = Mutex::new(Port::new(0x40));
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static CMD: Mutex<PortWriteOnly<u8>> = Mutex::new(PortWriteOnly::new(0x43));
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const MAX_FREQ: u32 = 1_193_180;
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pub fn init(mut freq: u32) {
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interrupts::register_handler(0, handler).unwrap();
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let mut div = MAX_FREQ / freq;
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if div > 65535 {
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println!("[PIT] Frequency of {}Hz too slow, min freq is 18 Hz", freq);
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div = 65535;
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freq = 18;
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} else if div == 0 {
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println!("[PIT] Frequency of {}Hz too fast, max freq is {} Hz", freq, MAX_FREQ);
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div = 1;
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freq = MAX_FREQ;
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}
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println!("[PIT] Setting PIT to {}Hz with divisor of {}", freq, div);
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// Command breakdown (MSB to LSB):
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// 00 - Channel 0
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// 11 - lobyte/hibyte access mode - set both bytes in one command
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// 011 - Mode 3, sqaure wave generator at frequency MAX_FREQ/div, generates interrupts at that
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// frequency
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// 0 - binary mode, always used
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unsafe { CMD.lock().write(0b0011_0110_u8) };
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unsafe { DATA.lock().write((div & 0xFF) as u8) };
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unsafe { DATA.lock().write(((div >> 8) & 0xFF) as u8) };
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}
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fn handler(_irq: u8, eoi_guard: EoiGuard) {
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drop(eoi_guard);
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if let Some(mut tasking) = TASKING.try_lock() {
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tasking.task_yield();
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}
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}
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