platform-uart.hh

Go to the documentation of this file.

#pragma once
 
#ifndef DEFAULT_UART_BAUD_RATE
#   define DEFAULT_UART_BAUD_RATE 921'600
#endif
 
#include <bitpack.hh>
#include <platform/concepts/uart.hh>
#include <utils.hh>
 
/**
 * \file
 */
 
/**
 * OpenTitan UART
 *
 * This peripheral's source and documentation can be found at:
 * https://github.com/lowRISC/opentitan/tree/ab878b5d3578939a04db72d4ed966a56a869b2ed/hw/ip/uart
 *
 * Rendered register documentation is served at:
 * https://opentitan.org/book/hw/ip/uart/doc/registers.html
 */
struct OpenTitanUart : private utils::NoCopyNoMove
{
    struct Interrupts : Bitpack<uint32_t>
    {
        BITPACK_USUAL_PREFIX;
        BITPACK_MEMBER_ADD_ENUM_BOOL_CLEARED_ASSERTED(TransmitWatermark, 0);
        BITPACK_MEMBER_ADD_ENUM_BOOL_CLEARED_ASSERTED(ReceiveWatermark, 1);
        BITPACK_MEMBER_ADD_ENUM_BOOL_CLEARED_ASSERTED(TransmitDone, 2);
        BITPACK_MEMBER_ADD_ENUM_BOOL_CLEARED_ASSERTED(ReceiveOverflowError, 3);
        BITPACK_MEMBER_ADD_ENUM_BOOL_CLEARED_ASSERTED(ReceiveFrameError, 4);
        BITPACK_MEMBER_ADD_ENUM_BOOL_CLEARED_ASSERTED(ReceiveBreakError, 5);
        BITPACK_MEMBER_ADD_ENUM_BOOL_CLEARED_ASSERTED(ReceiveTimeout, 6);
        BITPACK_MEMBER_ADD_ENUM_BOOL_CLEARED_ASSERTED(ReceiveParityError, 7);
        BITPACK_MEMBER_ADD_ENUM_BOOL_CLEARED_ASSERTED(TransmitEmpty, 8);
    };
 
    struct InterruptState : BitpackDerived<Interrupts>
    {
        BITPACK_DERIVED_PREFIX;
 
        // TransmitWatermark is a status, not an event, so RO, not RW1C.
        BITPACK_DERIVED_FIELD_CONST_FOR_TYPE(TransmitWatermark, true);
 
        // ReceiveWatermark is a status, not an event, so RO, not RW1C.
        BITPACK_DERIVED_FIELD_CONST_FOR_TYPE(ReceiveWatermark, true);
 
        // TransmitEmpty is a status, not an event, so RO, not RW1C.
        BITPACK_DERIVED_FIELD_CONST_FOR_TYPE(TransmitEmpty, true);
    };
 
    InterruptState interruptState;
    Interrupts     interruptEnable;
    Interrupts     interruptTest;
 
    /**
     * Alert Test Register (unused).
     */
    uint32_t alertTest;
 
    struct Control : Bitpack<uint32_t>
    {
        BITPACK_USUAL_PREFIX;
        BITPACK_MEMBER_ADD_ENUM_BOOL_DISABLED_ENABLED(Transmit, 0);
        BITPACK_MEMBER_ADD_ENUM_BOOL_DISABLED_ENABLED(Receive, 1);
        BITPACK_MEMBER_ADD_ENUM_BOOL_DISABLED_ENABLED(NoiseFilter, 2);
        BITPACK_MEMBER_ADD_ENUM_BOOL_DISABLED_ENABLED(SystemLoopback, 3);
        BITPACK_MEMBER_ADD_ENUM_BOOL_DISABLED_ENABLED(LineLoopback, 4);
        BITPACK_MEMBER_ADD_ENUM(Parity, uint8_t, 5, 6) {
            None = 0b00,
            Even = 0b01,
            Odd  = 0b11,
        };
 
        BITPACK_MEMBER_ADD_NUMERIC(BreakLevel, uint8_t, 8, 9);
        BITPACK_MEMBER_ADD_NUMERIC(Nco, uint16_t, 16, 31);
    } control;
 
    const struct Status : Bitpack<uint32_t>
    {
        BITPACK_USUAL_PREFIX;
        BITPACK_MEMBER_ADD_ENUM_BOOL_CLEARED_ASSERTED(TransmitFull, 0);
        BITPACK_MEMBER_ADD_ENUM_BOOL_CLEARED_ASSERTED(ReceiveFull, 1);
        BITPACK_MEMBER_ADD_ENUM_BOOL_CLEARED_ASSERTED(TransmitEmpty, 2);
        BITPACK_MEMBER_ADD_ENUM_BOOL_CLEARED_ASSERTED(TransmitIdle, 3);
        BITPACK_MEMBER_ADD_ENUM_BOOL_CLEARED_ASSERTED(ReceiveIdle, 4);
        BITPACK_MEMBER_ADD_ENUM_BOOL_CLEARED_ASSERTED(ReceiveEmpty, 5);
    } status; // NOLINT(readability-identifier-naming)
 
    /**
     * UART Read Data.
     */
    uint32_t readData;
    /**
     * UART Write Data.
     */
    uint32_t writeData;
 
    struct FIFOControl : Bitpack<uint32_t>
    {
        BITPACK_USUAL_PREFIX;
 
        BITPACK_MEMBER_ADD_ENUM_BOOL(Receive, AsIs, Reset, 0);
        BITPACK_MEMBER_ADD_ENUM_BOOL(Transmit, AsIs, Reset, 1);
 
        BITPACK_MEMBER_ADD_ENUM(ReceiveWatermark, uint8_t, 2, 4) {
            Level1  = 0b000,
            Level2  = 0b001,
            Level4  = 0b010,
            Level8  = 0b011,
            Level16 = 0b100,
            Level32 = 0b101,
            Level62 = 0b110,
        };
        BITPACK_MEMBER_ADD_ENUM(TransmitWatermark, uint8_t, 5, 7) {
            Level1  = 0b000,
            Level2  = 0b001,
            Level4  = 0b010,
            Level8  = 0b011,
            Level16 = 0b100,
        };
    } fifoControl;
 
    /**
     * UART FIFO Status Register.
     */
    const struct FIFOStatus : Bitpack<uint32_t>
    {
        BITPACK_USUAL_PREFIX;
 
        BITPACK_MEMBER_ADD_NUMERIC(TransmitLevel, uint8_t, 0, 7);
        BITPACK_MEMBER_ADD_NUMERIC(ReceiveLevel, uint8_t, 16, 23);
    } fifoStatus; // NOLINT(readability-identifier-naming)
 
    /**
     * Transmit Pin Override Control.
     *
     * Gives direct software control over the transmit pin state.
     */
    uint32_t override;
    /**
     * UART Oversampled Values.
     */
    uint32_t values;
    /**
     * UART Receive Timeout Control.
     */
    uint32_t timeoutControl;
 
    /**
     * Configure parity.
     *
     * When `enableParity` is set, parity will be enabled.
     * When `oddParity` is set, the odd parity will be used.
     */
    void parity(bool enableParity = true, bool oddParity = false) volatile
    {
        using enum Control::Parity;
        control.set(enableParity ? (oddParity ? Odd : Even) : None);
    }
 
    /**
     * Configure loopback.
     *
     * When `systemLoopback` is set, outgoing transmitted bits are routed back
     * the receiving line. When `lineLoopback` is set, incoming received bits
     * are forwarded to the transmit line.
     */
    void loopback(bool systemLoopback = true,
                  bool lineLoopback   = false) volatile
    {
        control.alter([=](auto v) {
            BITPACK_OPERATE_VALUE_DEPENDENT(
              v, =, SystemLoopback{systemLoopback});
            BITPACK_OPERATE_VALUE_DEPENDENT(v, =, LineLoopback{lineLoopback});
            return v;
        });
    }
 
    /// Clears the contents of the receive and transmit FIFOs.
    void fifos_clear() volatile
    {
        fifoControl.alter([](auto v) {
            BITPACK_OPERATE_VALUE_DECLTYPE(v, =, Transmit::Reset);
            BITPACK_OPERATE_VALUE_DECLTYPE(v, =, Receive::Reset);
            return v;
        });
    }
 
    /**
     * Sets the level transmit watermark.
     *
     * When the number of bytes in the transmit FIFO reach this level,
     * the transmit watermark interrupt will fire.
     */
    void transmit_watermark(FIFOControl::TransmitWatermark level) volatile
    {
        fifoControl.set(level);
    }
 
    /**
     * Sets the level receive watermark.
     *
     * When the number of bytes in the receive FIFO reach this level,
     * the receive watermark interrupt will fire.
     */
    void receive_watermark(FIFOControl::ReceiveWatermark level) volatile
    {
        fifoControl.set(level);
    }
 
    /// Enable the given interrupt by name
    template<typename Interrupt>
    void interrupt_enable() volatile
    {
        interruptEnable.member<Interrupt>() = Interrupt{true};
    }
 
    /// Disable the given interrupt by name
    template<typename Interrupt>
    void interrupt_disable() volatile
    {
        interruptEnable.member<Interrupt>() = Interrupt{false};
    }
 
    /// Enable the given interrupt(s) by value
    void interrupt_enable(Interrupts interrupt) volatile
    {
        interruptEnable.alter([interrupt](auto v) {
            return decltype(v){v.raw() | interrupt.raw()};
        });
    }
 
    /// Disable the given interrupt(s) by value
    void interrupt_disable(Interrupts interrupt) volatile
    {
        interruptEnable.alter([interrupt](auto v) {
            return decltype(v){v.raw() & ~interrupt.raw()};
        });
    }
 
    void init(unsigned baudRate = DEFAULT_UART_BAUD_RATE) volatile
    {
        // Nco = 2^20 * baud rate / cpu frequency
        const uint16_t Nco =
          ((static_cast<uint64_t>(baudRate) << 20) / CPU_TIMER_HZ);
 
        control.alter([=](auto v) {
            BITPACK_OPERATE_VALUE_DEPENDENT(v, =, Nco{Nco});
            BITPACK_OPERATE_VALUE_DECLTYPE(v, =, Transmit::Enabled);
            BITPACK_OPERATE_VALUE_DECLTYPE(v, =, Receive::Enabled);
            return v;
        });
    }
 
    /// Turn off the transceivers
    void disable() volatile
    {
        control.alter([=](auto v) {
            BITPACK_OPERATE_VALUE_DECLTYPE(v, =, Transmit::Disabled);
            BITPACK_OPERATE_VALUE_DECLTYPE(v, =, Receive::Disabled);
            return v;
        });
    }
 
    /**
     * Reset the control register to all zeros.  That disables the transceivers,
     * clears any loopbacks, disables parity, and so on.
     */
    void reset() volatile
    {
        control = decltype(control){0};
    }
 
    [[gnu::always_inline]] uint16_t transmit_fifo_level() volatile
    {
        return BITPACK_MEMBER_DECLTYPE(fifoStatus.read(), TransmitLevel).raw();
    }
 
    [[gnu::always_inline]] uint16_t receive_fifo_level() volatile
    {
        return BITPACK_MEMBER_DECLTYPE(fifoStatus.read(), ReceiveLevel).raw();
    }
 
    bool can_write() volatile
    {
        return BITPACK_OPERATE_VALUE_DECLTYPE(
          status.read(), ==, TransmitFull::Cleared);
    }
 
    bool can_read() volatile
    {
        return BITPACK_OPERATE_VALUE_DECLTYPE(
          status.read(), ==, ReceiveEmpty::Cleared);
    }
 
    /**
     * Write one byte, blocking until the byte is written.
     */
    void blocking_write(uint8_t byte) volatile
    {
        while (!can_write())
        {
        }
        writeData = byte;
    }
 
    /**
     * Read one byte, blocking until a byte is available.
     */
    uint8_t blocking_read() volatile
    {
        while (!can_read())
        {
        }
        return readData;
    }
};
 
#ifndef CHERIOT_PLATFORM_CUSTOM_UART
using Uart = OpenTitanUart;
static_assert(IsUart<Uart>);
#endif