Yifan Wu
3 years ago
parent
d3bd19867c
commit
53034d7c33
@ -0,0 +1,17 @@
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mod ns16550a;
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pub use ns16550a::NS16550a;
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use crate::board::CharDeviceImpl;
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use alloc::sync::Arc;
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use lazy_static::*;
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pub trait CharDevice {
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fn read(&self) -> u8;
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fn write(&self, ch: u8);
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fn handle_irq(&self);
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}
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lazy_static! {
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pub static ref UART: Arc<CharDeviceImpl> = Arc::new(CharDeviceImpl::new());
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}
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@ -0,0 +1,174 @@
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use super::CharDevice;
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use crate::sync::{Condvar, UPSafeCell};
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use alloc::collections::VecDeque;
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use bitflags::*;
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use volatile::{ReadOnly, Volatile, WriteOnly};
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///! Ref: https://www.lammertbies.nl/comm/info/serial-uart
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///! Ref: ns16550a datasheet: https://datasheetspdf.com/pdf-file/605590/NationalSemiconductor/NS16550A/1
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///! Ref: ns16450 datasheet: https://datasheetspdf.com/pdf-file/1311818/NationalSemiconductor/NS16450/1
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bitflags! {
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/// InterruptEnableRegister
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pub struct IER: u8 {
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const RX_AVALIABLE = 1 << 0;
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const TX_EMPTY = 1 << 1;
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}
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/// LineStatusRegister
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pub struct LSR: u8 {
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const DATA_AVAILABLE = 1 << 0;
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const THR_EMPTY = 1 << 5;
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}
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/// Model Control Register
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pub struct MCR: u8 {
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const DATA_TERMINAL_READY = 1 << 0;
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const REQUEST_TO_SEND = 1 << 1;
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const AUX_OUTPUT1 = 1 << 2;
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const AUX_OUTPUT2 = 1 << 3;
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}
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}
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#[repr(C)]
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#[allow(dead_code)]
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struct ReadWithoutDLAB {
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/// receiver buffer register
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pub rbr: ReadOnly<u8>,
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/// interrupt enable register
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pub ier: Volatile<IER>,
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/// interrupt identification register
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pub iir: ReadOnly<u8>,
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/// line control register
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pub lcr: Volatile<u8>,
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/// model control register
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pub mcr: Volatile<MCR>,
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/// line status register
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pub lsr: ReadOnly<LSR>,
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/// ignore MSR
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_padding1: ReadOnly<u8>,
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/// ignore SCR
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_padding2: ReadOnly<u8>,
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}
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#[repr(C)]
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#[allow(dead_code)]
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struct WriteWithoutDLAB {
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/// transmitter holding register
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pub thr: WriteOnly<u8>,
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/// interrupt enable register
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pub ier: Volatile<IER>,
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/// ignore FCR
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_padding0: ReadOnly<u8>,
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/// line control register
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pub lcr: Volatile<u8>,
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/// modem control register
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pub mcr: Volatile<MCR>,
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/// line status register
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pub lsr: ReadOnly<LSR>,
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/// ignore other registers
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_padding1: ReadOnly<u16>,
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}
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pub struct NS16550aRaw {
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base_addr: usize,
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}
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impl NS16550aRaw {
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fn read_end(&mut self) -> &mut ReadWithoutDLAB {
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unsafe { &mut *(self.base_addr as *mut ReadWithoutDLAB) }
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}
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fn write_end(&mut self) -> &mut WriteWithoutDLAB {
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unsafe { &mut *(self.base_addr as *mut WriteWithoutDLAB) }
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}
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pub fn new(base_addr: usize) -> Self {
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Self { base_addr }
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}
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pub fn init(&mut self) {
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let read_end = self.read_end();
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let mut mcr = MCR::empty();
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mcr |= MCR::DATA_TERMINAL_READY;
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mcr |= MCR::REQUEST_TO_SEND;
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mcr |= MCR::AUX_OUTPUT2;
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read_end.mcr.write(mcr);
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let ier = IER::RX_AVALIABLE;
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read_end.ier.write(ier);
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}
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pub fn read(&mut self) -> Option<u8> {
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let read_end = self.read_end();
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let lsr = read_end.lsr.read();
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if lsr.contains(LSR::DATA_AVAILABLE) {
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Some(read_end.rbr.read())
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} else {
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None
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}
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}
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pub fn write(&mut self, ch: u8) {
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let write_end = self.write_end();
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loop {
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if write_end.lsr.read().contains(LSR::THR_EMPTY) {
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write_end.thr.write(ch);
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break;
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}
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}
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}
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}
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struct NS16550aInner {
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ns16550a: NS16550aRaw,
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read_buffer: VecDeque<u8>,
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}
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pub struct NS16550a<const BASE_ADDR: usize> {
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inner: UPSafeCell<NS16550aInner>,
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condvar: Condvar,
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}
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impl<const BASE_ADDR: usize> NS16550a<BASE_ADDR> {
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pub fn new() -> Self {
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let mut inner = NS16550aInner {
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ns16550a: NS16550aRaw::new(BASE_ADDR),
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read_buffer: VecDeque::new(),
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};
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inner.ns16550a.init();
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Self {
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inner: unsafe { UPSafeCell::new(inner) },
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condvar: Condvar::new(),
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}
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}
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}
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impl<const BASE_ADDR: usize> CharDevice for NS16550a<BASE_ADDR> {
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fn read(&self) -> u8 {
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loop {
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let mut inner = self.inner.exclusive_access();
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if let Some(ch) = inner.read_buffer.pop_front() {
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return ch;
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} else {
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drop(inner);
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self.condvar.wait();
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}
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}
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}
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fn write(&self, ch: u8) {
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let mut inner = self.inner.exclusive_access();
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inner.ns16550a.write(ch);
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}
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fn handle_irq(&self) {
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let mut inner = self.inner.exclusive_access();
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let mut count = 0;
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while let Some(ch) = inner.ns16550a.read() {
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count += 1;
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inner.read_buffer.push_back(ch);
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}
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drop(inner);
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if count > 0 {
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self.condvar.signal();
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}
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}
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}
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@ -1,4 +1,6 @@
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pub mod block;
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pub mod chardev;
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pub mod plic;
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pub use block::BLOCK_DEVICE;
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pub use chardev::UART;
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