126 lines
3 KiB
Rust
126 lines
3 KiB
Rust
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use super::interrupt::{Interrupt, IrqBitmask};
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use super::sysbus::SysBus;
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use super::SyncedIoDevice;
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use num::FromPrimitive;
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#[derive(Debug, Default)]
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pub struct Timer {
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// registers
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pub timer_ctl: TimerCtl,
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pub timer_data: u16,
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timer_id: usize,
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reg: u32,
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target: u32,
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fired: bool,
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pub initial_data: u16,
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pub cycles: usize,
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}
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pub enum TimerAction {
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Overflow,
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Increment,
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}
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impl Timer {
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pub fn new(timer_id: usize) -> Timer {
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if timer_id > 3 {
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panic!("invalid timer id {}", timer_id);
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}
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Timer {
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timer_id: timer_id,
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..Timer::default()
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}
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}
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fn get_irq(&self) -> Interrupt {
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Interrupt::from_usize(self.timer_id + 8).unwrap()
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}
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fn frequency(&self) -> usize {
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match self.timer_ctl.prescalar() {
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0 => 1,
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1 => 64,
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2 => 256,
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3 => 1024,
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_ => unreachable!(),
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}
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}
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pub fn add_cycles(&mut self, cycles: usize, irqs: &mut IrqBitmask) -> TimerAction {
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self.cycles += cycles;
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let frequency = self.frequency();
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while self.cycles >= frequency {
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self.cycles -= frequency;
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self.timer_data = self.timer_data.wrapping_add(1);
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if self.timer_data == 0 {
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if self.timer_ctl.irq_enabled() {
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irqs.add_irq(self.get_irq());
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}
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println!("timer{} overflow", self.timer_id);
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return TimerAction::Overflow;
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}
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}
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return TimerAction::Increment;
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}
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}
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#[derive(Debug)]
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pub struct Timers([Timer; 4]);
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impl std::ops::Index<usize> for Timers {
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type Output = Timer;
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fn index(&self, index: usize) -> &Self::Output {
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&self.0[index]
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}
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}
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impl std::ops::IndexMut<usize> for Timers {
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fn index_mut(&mut self, index: usize) -> &mut Self::Output {
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&mut self.0[index]
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}
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}
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impl Timers {
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pub fn new() -> Timers {
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Timers([Timer::new(0), Timer::new(1), Timer::new(2), Timer::new(3)])
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}
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}
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impl SyncedIoDevice for Timers {
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fn step(&mut self, cycles: usize, _sb: &mut SysBus, irqs: &mut IrqBitmask) {
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for i in 0..4 {
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if self[i].timer_ctl.enabled() && !self[i].timer_ctl.cascade() {
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match self[i].add_cycles(cycles, irqs) {
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TimerAction::Overflow => match i {
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3 => {}
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_ => {
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let next_i = i +1;
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if self[next_i].timer_ctl.cascade() {
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println!("{:?} is cascade!", self[next_i]);
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self[next_i].add_cycles(1, irqs);
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}
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}
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},
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_ => {}
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}
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}
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}
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}
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}
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bitfield! {
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#[derive(Default)]
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pub struct TimerCtl(u16);
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impl Debug;
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u16;
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prescalar, _ : 1, 0;
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cascade, _ : 2;
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irq_enabled, _ : 6;
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enabled, set_enabled : 7;
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}
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