alioth 0.12.0

// Copyright 2024 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use std::collections::VecDeque;
use std::io::{Read, Write};
use std::sync::Arc;

use bitfield::bitfield;
use parking_lot::Mutex;

use crate::device::console::{Console, ConsoleThread, UartRecv};
use crate::device::ioapic::IoApic;
use crate::device::{self, MmioDev, Pause, Result};
use crate::hv::MsiSender;
use crate::mem::emulated::{Action, Mmio};
use crate::{bitflags, mem};

const TX_HOLDING_REGISTER: u16 = 0x0;
const RX_BUFFER_REGISTER: u16 = 0x0;
const DIVISOR_LATCH_LSB: u16 = 0x0;
const DIVISOR_LATCH_MSB: u16 = 0x1;
const INTERRUPT_ENABLE_REGISTER: u16 = 0x1;
const FIFO_CONTROL_REGISTER: u16 = 0x2;
const INTERRUPT_IDENTIFICATION_REGISTER: u16 = 0x2;
const LINE_CONTROL_REGISTER: u16 = 0x3;
const MODEM_CONTROL_REGISTER: u16 = 0x4;
const LINE_STATUS_REGISTER: u16 = 0x5;
const MODEM_STATUS_REGISTER: u16 = 0x6;
const SCRATCH_REGISTER: u16 = 0x7;

// offset 0x1, Interrupt Enable Register (IER)
bitflags! {
    #[derive(Default)]
    pub struct InterruptEnable(u8) {
        MODEM_STATUS = 1 << 3;
        RECEIVER_LINE_STATUS = 1 << 2;
        TX_HOLDING_REGISTER_EMPTY = 1 << 1;
        RECEIVED_DATA_AVAILABLE = 1 << 0;
    }
}

// offset 0x2, write, FIFO Control Register (FCR)
bitfield! {
    #[derive(Copy, Clone, Default)]
    pub struct FifoControl(u8);
    impl Debug;
    rx_trigger_size_bits, _: 7, 6;
    dma_mode, _: 3;
    tx_reset, _: 2;
    rx_reset, _: 1;
    fifo_enabled, _: 0;
}

impl FifoControl {
    pub fn rx_trigger_size(&self) -> usize {
        match self.rx_trigger_size_bits() {
            0b00 => 1,
            0b01 => 4,
            0b10 => 8,
            0b11 => 14,
            _ => unreachable!(),
        }
    }
}

// offset 0x2, read, Interrupt Identification Register
bitfield! {
    #[derive(Copy, Clone)]
    pub struct InterruptIdentification(u8);
    impl Debug;
    fifo_enabled, _: 7, 6;
    interrupt_id, set_interrupt_id: 3,1;
    no_pending, set_no_pending: 0; // Interrupt Pending Bit
}

impl InterruptIdentification {
    pub fn set_fifo_enabled(&mut self) {
        self.0 |= 0b11 << 6;
    }

    pub fn clear_fifi_enabled(&mut self) {
        self.0 &= !(0b11 << 6);
    }

    pub fn set_rx_data_available(&mut self) {
        self.0 = (self.0 & !0b1111) | 0b0100;
    }

    pub fn set_tx_room_empty(&mut self) {
        self.0 = (self.0 & !0b1111) | 0b0010;
    }

    pub fn clear_interrupt(&mut self) {
        self.0 = (self.0 & !0b1111) | 1;
    }
}

impl Default for InterruptIdentification {
    fn default() -> Self {
        let mut val = InterruptIdentification(0);
        val.clear_interrupt();
        val
    }
}

// offset 0x3, Line Control Register (LCR)
bitfield! {
    #[derive(Copy, Clone)]
    pub struct LineControl(u8);
    impl Debug;
    divisor_latch_access, _: 7;
    break_, _: 6;
    stick_parity, _: 5;
    even_parity, _: 4;
    parity_enabled, _: 3;
    step_bits, _: 2;
    word_length, _: 1, 0;
}

impl Default for LineControl {
    fn default() -> Self {
        LineControl(0b00000011) // 8 data bits as default
    }
}

// offset 0x4, Modem Control Register
bitfield! {
    #[derive(Copy, Clone, Default)]
    pub struct ModemControl(u8);
    impl Debug;
    loop_back, _: 4;
    out_2, _: 3;
    out_1, _: 2;
    request_to_send, _: 1;
    data_terminal_ready, _: 0; // Data Terminal Ready
}

// offset 0x5, Line Status Register (LSR)
bitflags! {
    pub struct LineStatus(u8) {
        ERROR_IN_RX_FIFO = 1 << 7;
        TX_EMPTY = 1 << 6;
        TX_HOLDING_REGISTER_EMPTY = 1 << 5;
        BREAK_INTERRUPT = 1 << 4;
        FRAMING_ERROR = 1 << 3;
        PARITY_ERROR = 1 << 2;
        OVERRUN_ERROR = 1 << 1;
        DATA_READY = 1 << 0;
    }
}

impl Default for LineStatus {
    fn default() -> Self {
        LineStatus::TX_EMPTY | LineStatus::TX_HOLDING_REGISTER_EMPTY
    }
}

#[derive(Default, Debug)]
struct SerialReg {
    interrupt_enable: InterruptEnable, // 0x1, Interrupt Enable Register (IER)
    #[allow(dead_code)]
    fifo_control: FifoControl, // 0x2, write, FIFO Control Register (FCR)
    interrupt_identification: InterruptIdentification, // 0x2, read, Interrupt Identification Register
    line_control: LineControl,                         // 0x3, Line Control Register (LCR)
    modem_control: ModemControl,                       // 0x4, Modem Control Register (MCR)
    line_status: LineStatus,
    modem_status: u8, // 0x6, Modem Status Register (MSR)
    scratch: u8,      // 0x7, Scratch Register (SCR)
    divisor: u16,
    data: VecDeque<u8>,
}

#[derive(Debug)]
pub struct Serial<M: MsiSender, C> {
    name: Arc<str>,
    io_apci: Arc<IoApic<M>>,
    pin: u8,
    reg: Arc<Mutex<SerialReg>>,
    console: Arc<C>,
    _thread: ConsoleThread,
}

impl<M, C> Mmio for Serial<M, C>
where
    M: MsiSender,
    C: Console,
    for<'a> &'a C: Read + Write,
{
    fn size(&self) -> u64 {
        8
    }

    fn read(&self, offset: u64, _size: u8) -> Result<u64, mem::Error> {
        let mut reg = self.reg.lock();
        let ret = match offset as u16 {
            DIVISOR_LATCH_LSB if reg.line_control.divisor_latch_access() => reg.divisor as u8,
            DIVISOR_LATCH_MSB if reg.line_control.divisor_latch_access() => {
                (reg.divisor >> 8) as u8
            }
            RX_BUFFER_REGISTER => {
                if reg.data.len() <= 1 {
                    reg.line_status &= !LineStatus::DATA_READY;
                }
                reg.data.pop_front().unwrap_or(0xff)
            }
            INTERRUPT_ENABLE_REGISTER => reg.interrupt_enable.bits(),
            INTERRUPT_IDENTIFICATION_REGISTER => {
                let ret = reg.interrupt_identification.0;
                reg.interrupt_identification.clear_interrupt();
                ret
            }
            LINE_CONTROL_REGISTER => reg.line_control.0,
            MODEM_CONTROL_REGISTER => reg.modem_control.0,
            LINE_STATUS_REGISTER => reg.line_status.bits(),
            MODEM_STATUS_REGISTER => reg.modem_status,
            SCRATCH_REGISTER => reg.scratch,
            _ => {
                log::error!("{}: read unreachable offset {offset:#x}", self.name,);
                0x0
            }
        };
        Ok(ret as u64)
    }

    fn write(&self, offset: u64, _size: u8, val: u64) -> mem::Result<Action> {
        let byte = val as u8;
        let mut reg = self.reg.lock();
        match offset as u16 {
            DIVISOR_LATCH_LSB if reg.line_control.divisor_latch_access() => {
                reg.divisor = (reg.divisor & 0xff00) | byte as u16;
            }
            DIVISOR_LATCH_MSB if reg.line_control.divisor_latch_access() => {
                reg.divisor = (reg.divisor & 0x00ff) | ((byte as u16) << 8);
            }
            TX_HOLDING_REGISTER => {
                if reg.modem_control.loop_back() {
                    reg.data.push_back(byte);
                    if reg
                        .interrupt_enable
                        .contains(InterruptEnable::RECEIVED_DATA_AVAILABLE)
                    {
                        reg.interrupt_identification.set_rx_data_available();
                        self.send_irq();
                    }
                    reg.line_status |= LineStatus::DATA_READY;
                } else {
                    let _ = self.console.as_ref().write(&[byte]);
                    if reg
                        .interrupt_enable
                        .contains(InterruptEnable::TX_HOLDING_REGISTER_EMPTY)
                    {
                        reg.interrupt_identification.set_tx_room_empty();
                        self.send_irq()
                    }
                }
            }
            INTERRUPT_ENABLE_REGISTER => {
                reg.interrupt_enable = InterruptEnable::from_bits_truncate(byte);
            }
            FIFO_CONTROL_REGISTER => {}
            LINE_CONTROL_REGISTER => {
                reg.line_control = LineControl(byte);
            }
            MODEM_CONTROL_REGISTER => {
                reg.modem_control = ModemControl(byte);
            }
            LINE_STATUS_REGISTER => {}
            MODEM_STATUS_REGISTER => {}
            SCRATCH_REGISTER => {
                reg.scratch = byte;
            }
            _ => log::error!("{}: write unreachable offset {:#x}", self.name, offset),
        }
        Ok(Action::None)
    }
}

impl<M, C> Pause for Serial<M, C>
where
    M: MsiSender,
{
    fn pause(&self) -> device::Result<()> {
        Ok(())
    }

    fn resume(&self) -> device::Result<()> {
        Ok(())
    }
}

impl<M, C> MmioDev for Serial<M, C>
where
    M: MsiSender,
    C: Console,
    for<'a> &'a C: Read + Write,
{
}

struct SerialRecv<M: MsiSender> {
    pub name: Arc<str>,
    pub io_apci: Arc<IoApic<M>>,
    pub pin: u8,
    pub reg: Arc<Mutex<SerialReg>>,
}

impl<M: MsiSender> UartRecv for SerialRecv<M> {
    fn receive(&self, bytes: &[u8]) {
        let mut reg = self.reg.lock();
        reg.data.extend(bytes);
        if reg
            .interrupt_enable
            .contains(InterruptEnable::RECEIVED_DATA_AVAILABLE)
        {
            reg.interrupt_identification.set_rx_data_available();
            if let Err(e) = self.io_apci.service_pin(self.pin) {
                log::error!("{}: sending interrupt: {e:?}", self.name);
            }
        }
        reg.line_status |= LineStatus::DATA_READY;
    }
}

impl<M, C> Serial<M, C>
where
    M: MsiSender,
    C: Console,
    for<'a> &'a C: Read + Write,
{
    pub fn new(base_port: u16, io_apci: Arc<IoApic<M>>, pin: u8, console: C) -> Result<Self> {
        let reg = Arc::new(Mutex::new(SerialReg::default()));
        let console = Arc::new(console);
        let name: Arc<str> = Arc::from(format!("serial_{base_port:#x}"));
        let uart_recv = SerialRecv {
            io_apci: io_apci.clone(),
            pin,
            name: name.clone(),
            reg: reg.clone(),
        };
        let thread = ConsoleThread::new(name.clone(), uart_recv, console.clone())?;
        let serial = Serial {
            name,
            reg,
            pin,
            io_apci,
            console,
            _thread: thread,
        };
        Ok(serial)
    }

    fn send_irq(&self) {
        if let Err(e) = self.io_apci.service_pin(self.pin) {
            log::error!("{}: sending interrupt: {e:?}", self.name);
        }
    }
}