Isa/IsaSerialDxe/Serial.c

/**@file
  Serial driver for standard UARTS on an ISA bus.

  Copyright (c) 2006 - 2007, Intel Corporation<BR>
  All rights reserved. This program and the accompanying materials
  are licensed and made available under the terms and conditions of the BSD License
  which accompanies this distribution.  The full text of the license may be found at
  http://opensource.org/licenses/bsd-license.php

  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

**/

#include "Serial.h"

//
// ISA Serial Driver Global Variables
//
EFI_DRIVER_BINDING_PROTOCOL gSerialControllerDriver = {
  SerialControllerDriverSupported,
  SerialControllerDriverStart,
  SerialControllerDriverStop,
  0xa,
  NULL,
  NULL
};


SERIAL_DEV  gSerialDevTempate = {
  SERIAL_DEV_SIGNATURE,
  NULL,
  { // SerialIo
    SERIAL_IO_INTERFACE_REVISION,
    IsaSerialReset,
    IsaSerialSetAttributes,
    IsaSerialSetControl,
    IsaSerialGetControl,
    IsaSerialWrite,
    IsaSerialRead,
    NULL
  },
  { // SerialMode
    SERIAL_PORT_DEFAULT_CONTROL_MASK,
    SERIAL_PORT_DEFAULT_TIMEOUT,
    FixedPcdGet64 (PcdUartDefaultBaudRate),     // BaudRate
    SERIAL_PORT_DEFAULT_RECEIVE_FIFO_DEPTH,
    FixedPcdGet8 (PcdUartDefaultDataBits),      // DataBits
    FixedPcdGet8 (PcdUartDefaultParity),        // Parity
    FixedPcdGet8 (PcdUartDefaultStopBits)       // StopBits
  },
  NULL,
  NULL,
  { // UartDevicePath
    {
      MESSAGING_DEVICE_PATH,
      MSG_UART_DP,
      {
        (UINT8) (sizeof (UART_DEVICE_PATH)),
        (UINT8) ((sizeof (UART_DEVICE_PATH)) >> 8)
      }
    },
    0,
    FixedPcdGet64 (PcdUartDefaultBaudRate),
    FixedPcdGet8 (PcdUartDefaultDataBits),
    FixedPcdGet8 (PcdUartDefaultParity),
    FixedPcdGet8 (PcdUartDefaultStopBits)
  },
  NULL,
  0,    //BaseAddress
  {
    0,
    0,
    SERIAL_MAX_BUFFER_SIZE,
    { 0 }
  },
  {
    0,
    0,
    SERIAL_MAX_BUFFER_SIZE,
    { 0 }
  },
  FALSE,
  FALSE,
  UART16550A,
  NULL
};

/**
  The user Entry Point for module IsaSerial. The user code starts with this function.

  @param[in] ImageHandle    The firmware allocated handle for the EFI image.
  @param[in] SystemTable    A pointer to the EFI System Table.

  @retval EFI_SUCCESS       The entry point is executed successfully.
  @retval other             Some error occurs when executing this entry point.

**/
EFI_STATUS
EFIAPI
InitializeIsaSerial (
  IN EFI_HANDLE           ImageHandle,
  IN EFI_SYSTEM_TABLE     *SystemTable
  )
{
  EFI_STATUS              Status;

  //
  // Install driver model protocol(s).
  //
  Status = EfiLibInstallDriverBindingComponentName2 (
             ImageHandle,
             SystemTable,
             &gSerialControllerDriver,
             ImageHandle,
             &gIsaSerialComponentName,
             &gIsaSerialComponentName2
             );
  ASSERT_EFI_ERROR (Status);


  return Status;
}

/**
  Check to see if this driver supports the given controller

  @param  This - A pointer to the EFI_DRIVER_BINDING_PROTOCOL instance.
  @param  Controller - The handle of the controller to test.
  @param  RemainingDevicePath - A pointer to the remaining portion of a device path.

  @return EFI_SUCCESS - This driver can support the given controller

**/
EFI_STATUS
EFIAPI
SerialControllerDriverSupported (
  IN EFI_DRIVER_BINDING_PROTOCOL    *This,
  IN EFI_HANDLE                     Controller,
  IN EFI_DEVICE_PATH_PROTOCOL       *RemainingDevicePath
  )

{
  EFI_STATUS                                Status;
  EFI_DEVICE_PATH_PROTOCOL                  *ParentDevicePath;
  EFI_ISA_IO_PROTOCOL                       *IsaIo;
  UART_DEVICE_PATH                          UartNode;

  //
  // Ignore the RemainingDevicePath
  //
  //
  // Open the IO Abstraction(s) needed to perform the supported test
  //
  Status = gBS->OpenProtocol (
                  Controller,
                  &gEfiDevicePathProtocolGuid,
                  (VOID **) &ParentDevicePath,
                  This->DriverBindingHandle,
                  Controller,
                  EFI_OPEN_PROTOCOL_BY_DRIVER
                  );
  if (Status == EFI_ALREADY_STARTED) {
    return EFI_SUCCESS;
  }

  if (EFI_ERROR (Status)) {
    return Status;
  }

  gBS->CloseProtocol (
         Controller,
         &gEfiDevicePathProtocolGuid,
         This->DriverBindingHandle,
         Controller
         );

  Status = gBS->OpenProtocol (
                  Controller,
                  &gEfiIsaIoProtocolGuid,
                  (VOID **) &IsaIo,
                  This->DriverBindingHandle,
                  Controller,
                  EFI_OPEN_PROTOCOL_BY_DRIVER
                  );

  if (Status == EFI_ALREADY_STARTED) {
    return EFI_SUCCESS;
  }

  if (EFI_ERROR (Status)) {
    return Status;
  }
  //
  // Use the ISA I/O Protocol to see if Controller is standard ISA UART that
  // can be managed by this driver.
  //
  Status = EFI_SUCCESS;
  if (IsaIo->ResourceList->Device.HID != EISA_PNP_ID (0x501)) {
    Status = EFI_UNSUPPORTED;
    goto Error;
  }
  //
  // Make sure RemainingDevicePath is valid
  //
  if (RemainingDevicePath != NULL) {
    Status = EFI_UNSUPPORTED;
    CopyMem (
      &UartNode,
      (UART_DEVICE_PATH *) RemainingDevicePath,
      sizeof (UART_DEVICE_PATH)
      );
    if (UartNode.Header.Type != MESSAGING_DEVICE_PATH ||
        UartNode.Header.SubType != MSG_UART_DP ||
        sizeof (UART_DEVICE_PATH) != DevicePathNodeLength ((EFI_DEVICE_PATH_PROTOCOL *) &UartNode)
                                      ) {
      goto Error;
    }

    if (UartNode.BaudRate > SERIAL_PORT_MAX_BAUD_RATE) {
      goto Error;
    }

    if (UartNode.Parity < NoParity || UartNode.Parity > SpaceParity) {
      goto Error;
    }

    if (UartNode.DataBits < 5 || UartNode.DataBits > 8) {
      goto Error;
    }

    if (UartNode.StopBits < OneStopBit || UartNode.StopBits > TwoStopBits) {
      goto Error;
    }

    if ((UartNode.DataBits == 5) && (UartNode.StopBits == TwoStopBits)) {
      goto Error;
    }

    if ((UartNode.DataBits >= 6) && (UartNode.DataBits <= 8) && (UartNode.StopBits == OneFiveStopBits)) {
      goto Error;
    }

    Status = EFI_SUCCESS;
  }

Error:
  //
  // Close the I/O Abstraction(s) used to perform the supported test
  //
  gBS->CloseProtocol (
         Controller,
         &gEfiIsaIoProtocolGuid,
         This->DriverBindingHandle,
         Controller
         );

  return Status;
}

/**
  Start to management the controller passed in

  @param  This - A pointer to the EFI_DRIVER_BINDING_PROTOCOL instance.
  @param  Controller - The handle of the controller to test.
  @param  RemainingDevicePath - A pointer to the remaining portion of a device path.

  @return EFI_SUCCESS - Driver is started successfully

**/
EFI_STATUS
EFIAPI
SerialControllerDriverStart (
  IN EFI_DRIVER_BINDING_PROTOCOL    *This,
  IN EFI_HANDLE                     Controller,
  IN EFI_DEVICE_PATH_PROTOCOL       *RemainingDevicePath
  )

{
  EFI_STATUS                          Status;
  EFI_ISA_IO_PROTOCOL                 *IsaIo;
  SERIAL_DEV                          *SerialDevice;
  UINTN                               Index;
  UART_DEVICE_PATH                    Node;
  EFI_DEVICE_PATH_PROTOCOL            *ParentDevicePath;
  EFI_OPEN_PROTOCOL_INFORMATION_ENTRY *OpenInfoBuffer;
  UINTN                               EntryCount;
  EFI_SERIAL_IO_PROTOCOL              *SerialIo;

  SerialDevice = NULL;
  //
  // Get the Parent Device Path
  //
  Status = gBS->OpenProtocol (
                  Controller,
                  &gEfiDevicePathProtocolGuid,
                  (VOID **) &ParentDevicePath,
                  This->DriverBindingHandle,
                  Controller,
                  EFI_OPEN_PROTOCOL_BY_DRIVER
                  );
  if (EFI_ERROR (Status) && Status != EFI_ALREADY_STARTED) {
    return Status;
  }
  //
  // Report status code enable the serial
  //
  REPORT_STATUS_CODE_WITH_DEVICE_PATH (
    EFI_PROGRESS_CODE,
    EFI_P_PC_ENABLE | EFI_PERIPHERAL_SERIAL_PORT,
    ParentDevicePath
    );

  //
  // Grab the IO abstraction we need to get any work done
  //
  Status = gBS->OpenProtocol (
                  Controller,
                  &gEfiIsaIoProtocolGuid,
                  (VOID **) &IsaIo,
                  This->DriverBindingHandle,
                  Controller,
                  EFI_OPEN_PROTOCOL_BY_DRIVER
                  );
  if (EFI_ERROR (Status) && Status != EFI_ALREADY_STARTED) {
    goto Error;
  }

  if (Status == EFI_ALREADY_STARTED) {

    if (RemainingDevicePath == NULL) {
      return EFI_SUCCESS;
    }
    //
    // Make sure a child handle does not already exist.  This driver can only
    // produce one child per serial port.
    //
    Status = gBS->OpenProtocolInformation (
                    Controller,
                    &gEfiIsaIoProtocolGuid,
                    &OpenInfoBuffer,
                    &EntryCount
                    );
    if (EFI_ERROR (Status)) {
      return Status;
    }

    Status = EFI_ALREADY_STARTED;
    for (Index = 0; Index < EntryCount; Index++) {
      if (OpenInfoBuffer[Index].Attributes & EFI_OPEN_PROTOCOL_BY_CHILD_CONTROLLER) {
        Status = gBS->OpenProtocol (
                        OpenInfoBuffer[Index].ControllerHandle,
                        &gEfiSerialIoProtocolGuid,
                        (VOID **) &SerialIo,
                        This->DriverBindingHandle,
                        Controller,
                        EFI_OPEN_PROTOCOL_GET_PROTOCOL
                        );
        if (!EFI_ERROR (Status)) {
          CopyMem (&Node, RemainingDevicePath, sizeof (UART_DEVICE_PATH));
          Status = SerialIo->SetAttributes (
                               SerialIo,
                               Node.BaudRate,
                               SerialIo->Mode->ReceiveFifoDepth,
                               SerialIo->Mode->Timeout,
                               (EFI_PARITY_TYPE) Node.Parity,
                               Node.DataBits,
                               (EFI_STOP_BITS_TYPE) Node.StopBits
                               );
        }
        break;
      }
    }

    gBS->FreePool (OpenInfoBuffer);
    return Status;
  }
  //
  // Initialize the serial device instance
  //
  SerialDevice = AllocateCopyPool (sizeof (SERIAL_DEV), &gSerialDevTempate);
  if (SerialDevice == NULL) {
    Status = EFI_OUT_OF_RESOURCES;
    goto Error;
  }

  SerialDevice->SerialIo.Mode       = &(SerialDevice->SerialMode);
  SerialDevice->IsaIo               = IsaIo;
  SerialDevice->ParentDevicePath    = ParentDevicePath;

  ADD_SERIAL_NAME (SerialDevice, IsaIo);

  for (Index = 0; SerialDevice->IsaIo->ResourceList->ResourceItem[Index].Type != EfiIsaAcpiResourceEndOfList; Index++) {
    if (SerialDevice->IsaIo->ResourceList->ResourceItem[Index].Type == EfiIsaAcpiResourceIo) {
      SerialDevice->BaseAddress = (UINT16) SerialDevice->IsaIo->ResourceList->ResourceItem[Index].StartRange;
    }
  }
  //
  // Report status code the serial present
  //
  REPORT_STATUS_CODE_WITH_DEVICE_PATH (
    EFI_PROGRESS_CODE,
    EFI_P_PC_PRESENCE_DETECT | EFI_PERIPHERAL_SERIAL_PORT,
    ParentDevicePath
    );

  if (!IsaSerialPortPresent (SerialDevice)) {
    Status = EFI_DEVICE_ERROR;
    REPORT_STATUS_CODE_WITH_DEVICE_PATH (
      EFI_ERROR_CODE,
      EFI_P_EC_NOT_DETECTED | EFI_PERIPHERAL_SERIAL_PORT,
      ParentDevicePath
      );
    goto Error;
  }

  if (RemainingDevicePath != NULL) {
    //
    // Match the configuration of the RemainingDevicePath. IsHandleSupported()
    // already checked to make sure the RemainingDevicePath contains settings
    // that we can support.
    //
    CopyMem (&SerialDevice->UartDevicePath, RemainingDevicePath, sizeof (UART_DEVICE_PATH));
  } else {
    //
    // Use the values from the gSerialDevTempate as no remaining device path was
    // passed in.
    //
  }
  //
  // Build the device path by appending the UART node to the ParentDevicePath
  // from the WinNtIo handle. The Uart setings are zero here, since
  // SetAttribute() will update them to match the current setings.
  //
  SerialDevice->DevicePath = AppendDevicePathNode (
                               ParentDevicePath,
                               (EFI_DEVICE_PATH_PROTOCOL *)&SerialDevice->UartDevicePath
                               );
  if (SerialDevice->DevicePath == NULL) {
    Status = EFI_DEVICE_ERROR;
    goto Error;
  }

  //
  // Fill in Serial I/O Mode structure based on either the RemainingDevicePath or defaults.
  //
  SerialDevice->SerialMode.BaudRate         = SerialDevice->UartDevicePath.BaudRate;
  SerialDevice->SerialMode.DataBits         = SerialDevice->UartDevicePath.DataBits;
  SerialDevice->SerialMode.Parity           = SerialDevice->UartDevicePath.Parity;
  SerialDevice->SerialMode.StopBits         = SerialDevice->UartDevicePath.StopBits;

  //
  // Issue a reset to initialize the COM port
  //
  Status = SerialDevice->SerialIo.Reset (&SerialDevice->SerialIo);
  if (EFI_ERROR (Status)) {
    REPORT_STATUS_CODE_WITH_DEVICE_PATH (
      EFI_ERROR_CODE,
      EFI_P_EC_CONTROLLER_ERROR | EFI_PERIPHERAL_SERIAL_PORT,
      ParentDevicePath
      );
    goto Error;
  }
  //
  // Install protocol interfaces for the serial device.
  //
  Status = gBS->InstallMultipleProtocolInterfaces (
                  &SerialDevice->Handle,
                  &gEfiDevicePathProtocolGuid,
                  SerialDevice->DevicePath,
                  &gEfiSerialIoProtocolGuid,
                  &SerialDevice->SerialIo,
                  NULL
                  );
  if (EFI_ERROR (Status)) {
    goto Error;
  }
  //
  // Open For Child Device
  //
  Status = gBS->OpenProtocol (
                  Controller,
                  &gEfiIsaIoProtocolGuid,
                  (VOID **) &IsaIo,
                  This->DriverBindingHandle,
                  SerialDevice->Handle,
                  EFI_OPEN_PROTOCOL_BY_CHILD_CONTROLLER
                  );

Error:
  if (EFI_ERROR (Status)) {
    gBS->CloseProtocol (
           Controller,
           &gEfiDevicePathProtocolGuid,
           This->DriverBindingHandle,
           Controller
           );
    gBS->CloseProtocol (
           Controller,
           &gEfiIsaIoProtocolGuid,
           This->DriverBindingHandle,
           Controller
           );
    if (SerialDevice) {
      if (SerialDevice->DevicePath) {
        gBS->FreePool (SerialDevice->DevicePath);
      }

      FreeUnicodeStringTable (SerialDevice->ControllerNameTable);
      gBS->FreePool (SerialDevice);
    }
  }

  return Status;
}

/**
  Disconnect this driver with the controller, uninstall related protocol instance

  @param  This                - A pointer to the EFI_DRIVER_BINDING_PROTOCOL instance.
  @param  Controller          - The handle of the controller to test.
  @param  NumberOfChildren    - Number of child device.
  @param  ChildHandleBuffer   - A pointer to the remaining portion of a device path.

  @retval EFI_SUCCESS         - Operation successfully
  @retval EFI_DEVICE_ERROR    - Cannot stop the driver successfully

**/
EFI_STATUS
EFIAPI
SerialControllerDriverStop (
  IN  EFI_DRIVER_BINDING_PROTOCOL    *This,
  IN  EFI_HANDLE                     Controller,
  IN  UINTN                          NumberOfChildren,
  IN  EFI_HANDLE                     *ChildHandleBuffer
  )

{
  EFI_STATUS                          Status;
  UINTN                               Index;
  BOOLEAN                             AllChildrenStopped;
  EFI_SERIAL_IO_PROTOCOL              *SerialIo;
  SERIAL_DEV                          *SerialDevice;
  EFI_ISA_IO_PROTOCOL                 *IsaIo;
  EFI_DEVICE_PATH_PROTOCOL            *DevicePath;

  Status = gBS->HandleProtocol (
                  Controller,
                  &gEfiDevicePathProtocolGuid,
                  (VOID **) &DevicePath
                  );

  //
  // Report the status code disable the serial
  //
  REPORT_STATUS_CODE_WITH_DEVICE_PATH (
    EFI_PROGRESS_CODE,
    EFI_P_PC_DISABLE | EFI_PERIPHERAL_SERIAL_PORT,
    DevicePath
    );

  //
  // Complete all outstanding transactions to Controller.
  // Don't allow any new transaction to Controller to be started.
  //
  if (NumberOfChildren == 0) {
    //
    // Close the bus driver
    //
    Status = gBS->CloseProtocol (
                    Controller,
                    &gEfiIsaIoProtocolGuid,
                    This->DriverBindingHandle,
                    Controller
                    );

    Status = gBS->CloseProtocol (
                    Controller,
                    &gEfiDevicePathProtocolGuid,
                    This->DriverBindingHandle,
                    Controller
                    );
    return Status;
  }

  AllChildrenStopped = TRUE;

  for (Index = 0; Index < NumberOfChildren; Index++) {

    Status = gBS->OpenProtocol (
                    ChildHandleBuffer[Index],
                    &gEfiSerialIoProtocolGuid,
                    (VOID **) &SerialIo,
                    This->DriverBindingHandle,
                    Controller,
                    EFI_OPEN_PROTOCOL_GET_PROTOCOL
                    );
    if (!EFI_ERROR (Status)) {

      SerialDevice = SERIAL_DEV_FROM_THIS (SerialIo);

      Status = gBS->CloseProtocol (
                      Controller,
                      &gEfiIsaIoProtocolGuid,
                      This->DriverBindingHandle,
                      ChildHandleBuffer[Index]
                      );

      Status = gBS->UninstallMultipleProtocolInterfaces (
                      ChildHandleBuffer[Index],
                      &gEfiDevicePathProtocolGuid,
                      SerialDevice->DevicePath,
                      &gEfiSerialIoProtocolGuid,
                      &SerialDevice->SerialIo,
                      NULL
                      );
      if (EFI_ERROR (Status)) {
        gBS->OpenProtocol (
               Controller,
               &gEfiIsaIoProtocolGuid,
               (VOID **) &IsaIo,
               This->DriverBindingHandle,
               ChildHandleBuffer[Index],
               EFI_OPEN_PROTOCOL_BY_CHILD_CONTROLLER
               );
      } else {
        if (SerialDevice->DevicePath) {
          gBS->FreePool (SerialDevice->DevicePath);
        }

        FreeUnicodeStringTable (SerialDevice->ControllerNameTable);
        gBS->FreePool (SerialDevice);
      }
    }

    if (EFI_ERROR (Status)) {
      AllChildrenStopped = FALSE;
    }
  }

  if (!AllChildrenStopped) {
    return EFI_DEVICE_ERROR;
  }

  return EFI_SUCCESS;
}

/**
  Detect whether specific FIFO is full or not

  @param Fifo  - A pointer to the Data Structure SERIAL_DEV_FIFO

  @return whether specific FIFO is full or not

**/
BOOLEAN
IsaSerialFifoFull (
  IN SERIAL_DEV_FIFO *Fifo
  )

{
  if (Fifo->Surplus == 0) {
    return TRUE;
  }

  return FALSE;
}

/**
  Detect whether specific FIFO is empty or not


  @param  Fifo  - A pointer to the Data Structure SERIAL_DEV_FIFO

  @return whether specific FIFO is empty or not

**/
BOOLEAN
IsaSerialFifoEmpty (
  IN SERIAL_DEV_FIFO *Fifo
  )

{
  if (Fifo->Surplus == SERIAL_MAX_BUFFER_SIZE) {
    return TRUE;
  }

  return FALSE;
}

/**
  Add data to specific FIFO

  @param Fifo                - A pointer to the Data Structure SERIAL_DEV_FIFO
  @param Data                - the data added to FIFO

  @retval EFI_SUCCESS         - Add data to specific FIFO successfully
  @retval EFI_OUT_OF_RESOURCE - Failed to add data because FIFO is already full

**/
EFI_STATUS
IsaSerialFifoAdd (
  IN SERIAL_DEV_FIFO *Fifo,
  IN UINT8           Data
  )

{
  //
  // if FIFO full can not add data
  //
  if (IsaSerialFifoFull (Fifo)) {
    return EFI_OUT_OF_RESOURCES;
  }
  //
  // FIFO is not full can add data
  //
  Fifo->Data[Fifo->Last] = Data;
  Fifo->Surplus--;
  Fifo->Last++;
  if (Fifo->Last == SERIAL_MAX_BUFFER_SIZE) {
    Fifo->Last = 0;
  }

  return EFI_SUCCESS;
}

/**
  Remove data from specific FIFO

  @param Fifo                - A pointer to the Data Structure SERIAL_DEV_FIFO
  @param Data                - the data removed from FIFO

  @retval EFI_SUCCESS         - Remove data from specific FIFO successfully
  @retval EFI_OUT_OF_RESOURCE - Failed to remove data because FIFO is empty

**/
EFI_STATUS
IsaSerialFifoRemove (
  IN  SERIAL_DEV_FIFO *Fifo,
  OUT UINT8           *Data
  )

{
  //
  // if FIFO is empty, no data can remove
  //
  if (IsaSerialFifoEmpty (Fifo)) {
    return EFI_OUT_OF_RESOURCES;
  }
  //
  // FIFO is not empty, can remove data
  //
  *Data = Fifo->Data[Fifo->First];
  Fifo->Surplus++;
  Fifo->First++;
  if (Fifo->First == SERIAL_MAX_BUFFER_SIZE) {
    Fifo->First = 0;
  }

  return EFI_SUCCESS;
}

/**
  Reads and writes all avaliable data.

  @param SerialDevice         - The device to flush

  @retval EFI_SUCCESS         - Data was read/written successfully.
  @retval EFI_OUT_OF_RESOURCE - Failed because software receive FIFO is full.  Note, when
                                this happens, pending writes are not done.

**/
EFI_STATUS
IsaSerialReceiveTransmit (
  IN SERIAL_DEV *SerialDevice
  )

{
  SERIAL_PORT_LSR Lsr;
  UINT8           Data;
  BOOLEAN         ReceiveFifoFull;
  SERIAL_PORT_MSR Msr;
  SERIAL_PORT_MCR Mcr;
  UINTN           TimeOut;

  Data = 0;

  //
  // Begin the read or write
  //
  if (SerialDevice->SoftwareLoopbackEnable) {
    do {
      ReceiveFifoFull = IsaSerialFifoFull (&SerialDevice->Receive);
      if (!IsaSerialFifoEmpty (&SerialDevice->Transmit)) {
        IsaSerialFifoRemove (&SerialDevice->Transmit, &Data);
        if (ReceiveFifoFull) {
          return EFI_OUT_OF_RESOURCES;
        }

        IsaSerialFifoAdd (&SerialDevice->Receive, Data);
      }
    } while (!IsaSerialFifoEmpty (&SerialDevice->Transmit));
  } else {
    ReceiveFifoFull = IsaSerialFifoFull (&SerialDevice->Receive);
    do {
      Lsr.Data = READ_LSR (SerialDevice->IsaIo, SerialDevice->BaseAddress);

      //
      // Flush incomming data to prevent a an overrun during a long write
      //
      if (Lsr.Bits.DR && !ReceiveFifoFull) {
        ReceiveFifoFull = IsaSerialFifoFull (&SerialDevice->Receive);
        if (!ReceiveFifoFull) {
          if (Lsr.Bits.FIFOE || Lsr.Bits.OE || Lsr.Bits.PE || Lsr.Bits.FE || Lsr.Bits.BI) {
            REPORT_STATUS_CODE_WITH_DEVICE_PATH (
              EFI_ERROR_CODE,
              EFI_P_EC_INPUT_ERROR | EFI_PERIPHERAL_SERIAL_PORT,
              SerialDevice->DevicePath
              );
            if (Lsr.Bits.FIFOE || Lsr.Bits.PE || Lsr.Bits.FE || Lsr.Bits.BI) {
              Data = READ_RBR (SerialDevice->IsaIo, SerialDevice->BaseAddress);
              continue;
            }
          }
          //
          // Make sure the receive data will not be missed, Assert DTR
          //
          if (SerialDevice->HardwareFlowControl) {
            Mcr.Data = READ_MCR (SerialDevice->IsaIo, SerialDevice->BaseAddress);
            Mcr.Bits.DTRC &= 0;
            WRITE_MCR (SerialDevice->IsaIo, SerialDevice->BaseAddress, Mcr.Data);
          }

          Data = READ_RBR (SerialDevice->IsaIo, SerialDevice->BaseAddress);

          //
          // Deassert DTR
          //
          if (SerialDevice->HardwareFlowControl) {
            Mcr.Data = READ_MCR (SerialDevice->IsaIo, SerialDevice->BaseAddress);
            Mcr.Bits.DTRC |= 1;
            WRITE_MCR (SerialDevice->IsaIo, SerialDevice->BaseAddress, Mcr.Data);
          }

          IsaSerialFifoAdd (&SerialDevice->Receive, Data);

          continue;
        } else {
          REPORT_STATUS_CODE_WITH_DEVICE_PATH (
            EFI_PROGRESS_CODE,
            EFI_P_SERIAL_PORT_PC_CLEAR_BUFFER | EFI_PERIPHERAL_SERIAL_PORT,
            SerialDevice->DevicePath
            );
        }
      }
      //
      // Do the write
      //
      if (Lsr.Bits.THRE && !IsaSerialFifoEmpty (&SerialDevice->Transmit)) {
        //
        // Make sure the transmit data will not be missed
        //
        if (SerialDevice->HardwareFlowControl) {
          //
          // Send RTS
          //
          Mcr.Data = READ_MCR (SerialDevice->IsaIo, SerialDevice->BaseAddress);
          Mcr.Bits.RTS |= 1;
          WRITE_MCR (SerialDevice->IsaIo, SerialDevice->BaseAddress, Mcr.Data);
          //
          // Wait for CTS
          //
          TimeOut   = 0;
          Msr.Data  = READ_MSR (SerialDevice->IsaIo, SerialDevice->BaseAddress);
          while (!Msr.Bits.CTS) {
            gBS->Stall (TIMEOUT_STALL_INTERVAL);
            TimeOut++;
            if (TimeOut > 5) {
              break;
            }

            Msr.Data = READ_MSR (SerialDevice->IsaIo, SerialDevice->BaseAddress);
          }

          if (Msr.Bits.CTS) {
            IsaSerialFifoRemove (&SerialDevice->Transmit, &Data);
            WRITE_THR (SerialDevice->IsaIo, SerialDevice->BaseAddress, Data);
          }
        }
        //
        // write the data out
        //
        if (!SerialDevice->HardwareFlowControl) {
          IsaSerialFifoRemove (&SerialDevice->Transmit, &Data);
          WRITE_THR (SerialDevice->IsaIo, SerialDevice->BaseAddress, Data);
        }
        //
        // Make sure the transmit data will not be missed
        //
        if (SerialDevice->HardwareFlowControl) {
          //
          // Assert RTS
          //
          Mcr.Data = READ_MCR (SerialDevice->IsaIo, SerialDevice->BaseAddress);
          Mcr.Bits.RTS &= 0;
          WRITE_MCR (SerialDevice->IsaIo, SerialDevice->BaseAddress, Mcr.Data);
        }
      }
    } while (Lsr.Bits.THRE && !IsaSerialFifoEmpty (&SerialDevice->Transmit));
  }

  return EFI_SUCCESS;
}

//
// Interface Functions
//
/**
  Reset serial device

  @param This             - Pointer to EFI_SERIAL_IO_PROTOCOL

  @retval EFI_SUCCESS      - Reset successfully
  @retval EFI_DEVICE_ERROR - Failed to reset

**/
EFI_STATUS
EFIAPI
IsaSerialReset (
  IN EFI_SERIAL_IO_PROTOCOL  *This
  )
{
  EFI_STATUS      Status;
  SERIAL_DEV      *SerialDevice;
  SERIAL_PORT_LCR Lcr;
  SERIAL_PORT_IER Ier;
  SERIAL_PORT_MCR Mcr;
  SERIAL_PORT_FCR Fcr;
  EFI_TPL         Tpl;

  SerialDevice = SERIAL_DEV_FROM_THIS (This);

  //
  // Report the status code reset the serial
  //
  REPORT_STATUS_CODE_WITH_DEVICE_PATH (
    EFI_PROGRESS_CODE,
    EFI_P_PC_RESET | EFI_PERIPHERAL_SERIAL_PORT,
    SerialDevice->DevicePath
    );

  Tpl = gBS->RaiseTPL (TPL_NOTIFY);

  //
  // Make sure DLAB is 0.
  //
  Lcr.Data      = READ_LCR (SerialDevice->IsaIo, SerialDevice->BaseAddress);
  Lcr.Bits.DLAB = 0;
  WRITE_LCR (SerialDevice->IsaIo, SerialDevice->BaseAddress, Lcr.Data);

  //
  // Turn off all interrupts
  //
  Ier.Data        = READ_IER (SerialDevice->IsaIo, SerialDevice->BaseAddress);
  Ier.Bits.RAVIE  = 0;
  Ier.Bits.THEIE  = 0;
  Ier.Bits.RIE    = 0;
  Ier.Bits.MIE    = 0;
  WRITE_IER (SerialDevice->IsaIo, SerialDevice->BaseAddress, Ier.Data);

  //
  // Disable the FIFO.
  //
  Fcr.Bits.TRFIFOE = 0;
  WRITE_FCR (SerialDevice->IsaIo, SerialDevice->BaseAddress, Fcr.Data);

  //
  // Turn off loopback and disable device interrupt.
  //
  Mcr.Data      = READ_MCR (SerialDevice->IsaIo, SerialDevice->BaseAddress);
  Mcr.Bits.OUT1 = 0;
  Mcr.Bits.OUT2 = 0;
  Mcr.Bits.LME  = 0;
  WRITE_MCR (SerialDevice->IsaIo, SerialDevice->BaseAddress, Mcr.Data);

  //
  // Clear the scratch pad register
  //
  WRITE_SCR (SerialDevice->IsaIo, SerialDevice->BaseAddress, 0);

  //
  // Go set the current attributes
  //
  Status = This->SetAttributes (
                   This,
                   This->Mode->BaudRate,
                   This->Mode->ReceiveFifoDepth,
                   This->Mode->Timeout,
                   (EFI_PARITY_TYPE) This->Mode->Parity,
                   (UINT8) This->Mode->DataBits,
                   (EFI_STOP_BITS_TYPE) This->Mode->StopBits
                   );

  if (EFI_ERROR (Status)) {
    gBS->RestoreTPL (Tpl);
    return EFI_DEVICE_ERROR;
  }
  //
  // Go set the current control bits
  //
  Status = This->SetControl (
                   This,
                   This->Mode->ControlMask
                   );

  if (EFI_ERROR (Status)) {
    gBS->RestoreTPL (Tpl);
    return EFI_DEVICE_ERROR;
  }
  //
  // for 16550A enable FIFO, 16550 disable FIFO
  //
  Fcr.Bits.TRFIFOE  = 1;
  Fcr.Bits.RESETRF  = 1;
  Fcr.Bits.RESETTF  = 1;
  WRITE_FCR (SerialDevice->IsaIo, SerialDevice->BaseAddress, Fcr.Data);

  //
  // Reset the software FIFO
  //
  SerialDevice->Receive.First     = 0;
  SerialDevice->Receive.Last      = 0;
  SerialDevice->Receive.Surplus   = SERIAL_MAX_BUFFER_SIZE;
  SerialDevice->Transmit.First    = 0;
  SerialDevice->Transmit.Last     = 0;
  SerialDevice->Transmit.Surplus  = SERIAL_MAX_BUFFER_SIZE;

  gBS->RestoreTPL (Tpl);

  //
  // Device reset is complete
  //
  return EFI_SUCCESS;
}

/**
  Set new attributes to a serial device

  @param This                   - Pointer to EFI_SERIAL_IO_PROTOCOL
  @param  BaudRate               - The baudrate of the serial device
  @param  ReceiveFifoDepth       - The depth of receive FIFO buffer
  @param  Timeout                - The request timeout for a single char
  @param  Parity                 - The type of parity used in serial device
  @param  DataBits               - Number of databits used in serial device
  @param  StopBits               - Number of stopbits used in serial device

  @retval  EFI_SUCCESS            - The new attributes were set
  @retval  EFI_INVALID_PARAMETERS - One or more attributes have an unsupported value
  @retval  EFI_UNSUPPORTED        - Data Bits can not set to 5 or 6
  @retval  EFI_DEVICE_ERROR       - The serial device is not functioning correctly (no return)

**/
EFI_STATUS
EFIAPI
IsaSerialSetAttributes (
  IN EFI_SERIAL_IO_PROTOCOL  *This,
  IN UINT64                  BaudRate,
  IN UINT32                  ReceiveFifoDepth,
  IN UINT32                  Timeout,
  IN EFI_PARITY_TYPE         Parity,
  IN UINT8                   DataBits,
  IN EFI_STOP_BITS_TYPE      StopBits
  )
{
  EFI_STATUS                Status;
  SERIAL_DEV                *SerialDevice;
  UINT32                    Divisor;
  UINT32                    Remained;
  SERIAL_PORT_LCR           Lcr;
  EFI_DEVICE_PATH_PROTOCOL  *NewDevicePath;
  EFI_TPL                   Tpl;

  SerialDevice = SERIAL_DEV_FROM_THIS (This);

  //
  // Check for default settings and fill in actual values.
  //
  if (BaudRate == 0) {
    BaudRate = FixedPcdGet64 (PcdUartDefaultBaudRate);
  }

  if (ReceiveFifoDepth == 0) {
    ReceiveFifoDepth = SERIAL_PORT_DEFAULT_RECEIVE_FIFO_DEPTH;
  }

  if (Timeout == 0) {
    Timeout = SERIAL_PORT_DEFAULT_TIMEOUT;
  }

  if (Parity == DefaultParity) {
    Parity = (EFI_PARITY_TYPE)FixedPcdGet8 (PcdUartDefaultParity);
  }

  if (DataBits == 0) {
    DataBits = FixedPcdGet8 (PcdUartDefaultDataBits);
  }

  if (StopBits == DefaultStopBits) {
    StopBits = (EFI_STOP_BITS_TYPE) FixedPcdGet8 (PcdUartDefaultStopBits);
  }
  //
  // 5 and 6 data bits can not be verified on a 16550A UART
  // Return EFI_INVALID_PARAMETER if an attempt is made to use these settings.
  //
  if ((DataBits == 5) || (DataBits == 6)) {
    return EFI_INVALID_PARAMETER;
  }
  //
  // Make sure all parameters are valid
  //
  if ((BaudRate > SERIAL_PORT_MAX_BAUD_RATE) || (BaudRate < SERIAL_PORT_MIN_BAUD_RATE)) {
    return EFI_INVALID_PARAMETER;
  }
  //
  // 50,75,110,134,150,300,600,1200,1800,2000,2400,3600,4800,7200,9600,19200,
  // 38400,57600,115200
  //
  if (BaudRate < 75) {
    BaudRate = 50;
  } else if (BaudRate < 110) {
    BaudRate = 75;
  } else if (BaudRate < 134) {
    BaudRate = 110;
  } else if (BaudRate < 150) {
    BaudRate = 134;
  } else if (BaudRate < 300) {
    BaudRate = 150;
  } else if (BaudRate < 600) {
    BaudRate = 300;
  } else if (BaudRate < 1200) {
    BaudRate = 600;
  } else if (BaudRate < 1800) {
    BaudRate = 1200;
  } else if (BaudRate < 2000) {
    BaudRate = 1800;
  } else if (BaudRate < 2400) {
    BaudRate = 2000;
  } else if (BaudRate < 3600) {
    BaudRate = 2400;
  } else if (BaudRate < 4800) {
    BaudRate = 3600;
  } else if (BaudRate < 7200) {
    BaudRate = 4800;
  } else if (BaudRate < 9600) {
    BaudRate = 7200;
  } else if (BaudRate < 19200) {
    BaudRate = 9600;
  } else if (BaudRate < 38400) {
    BaudRate = 19200;
  } else if (BaudRate < 57600) {
    BaudRate = 38400;
  } else if (BaudRate < 115200) {
    BaudRate = 57600;
  } else if (BaudRate <= SERIAL_PORT_MAX_BAUD_RATE) {
    BaudRate = 115200;
  }

  if ((ReceiveFifoDepth < 1) || (ReceiveFifoDepth > SERIAL_PORT_MAX_RECEIVE_FIFO_DEPTH)) {
    return EFI_INVALID_PARAMETER;
  }

  if ((Timeout < SERIAL_PORT_MIN_TIMEOUT) || (Timeout > SERIAL_PORT_MAX_TIMEOUT)) {
    return EFI_INVALID_PARAMETER;
  }

  if ((Parity < NoParity) || (Parity > SpaceParity)) {
    return EFI_INVALID_PARAMETER;
  }

  if ((DataBits < 5) || (DataBits > 8)) {
    return EFI_INVALID_PARAMETER;
  }

  if ((StopBits < OneStopBit) || (StopBits > TwoStopBits)) {
    return EFI_INVALID_PARAMETER;
  }
  //
  // for DataBits = 5, StopBits can not set TwoStopBits
  //
  // if ((DataBits == 5) && (StopBits == TwoStopBits)) {
  //  return EFI_INVALID_PARAMETER;
  // }
  //
  // for DataBits = 6,7,8, StopBits can not set OneFiveStopBits
  //
  if ((DataBits >= 6) && (DataBits <= 8) && (StopBits == OneFiveStopBits)) {
    return EFI_INVALID_PARAMETER;
  }

  //
  // Compute divisor use to program the baud rate using a round determination
  //
  Divisor = (UINT32) DivU64x32Remainder (
                       SERIAL_PORT_INPUT_CLOCK,
                       ((UINT32) BaudRate * 16),
                       &Remained
                       );
  if (Remained) {
    Divisor += 1;
  }

  if ((Divisor == 0) || (Divisor & 0xffff0000)) {
    return EFI_INVALID_PARAMETER;
  }

  Tpl = gBS->RaiseTPL (TPL_NOTIFY);

  //
  // Compute the actual baud rate that the serial port will be programmed for.
  //
  BaudRate = SERIAL_PORT_INPUT_CLOCK / Divisor / 16;

  //
  // Put serial port on Divisor Latch Mode
  //
  Lcr.Data      = READ_LCR (SerialDevice->IsaIo, SerialDevice->BaseAddress);
  Lcr.Bits.DLAB = 1;
  WRITE_LCR (SerialDevice->IsaIo, SerialDevice->BaseAddress, Lcr.Data);

  //
  // Write the divisor to the serial port
  //
  WRITE_DLL (SerialDevice->IsaIo, SerialDevice->BaseAddress, (UINT8) (Divisor & 0xff));
  WRITE_DLM (SerialDevice->IsaIo, SerialDevice->BaseAddress, (UINT8) ((Divisor >> 8) & 0xff));

  //
  // Put serial port back in normal mode and set remaining attributes.
  //
  Lcr.Bits.DLAB = 0;

  switch (Parity) {
  case NoParity:
    Lcr.Bits.PAREN    = 0;
    Lcr.Bits.EVENPAR  = 0;
    Lcr.Bits.STICPAR  = 0;
    break;

  case EvenParity:
    Lcr.Bits.PAREN    = 1;
    Lcr.Bits.EVENPAR  = 1;
    Lcr.Bits.STICPAR  = 0;
    break;

  case OddParity:
    Lcr.Bits.PAREN    = 1;
    Lcr.Bits.EVENPAR  = 0;
    Lcr.Bits.STICPAR  = 0;
    break;

  case SpaceParity:
    Lcr.Bits.PAREN    = 1;
    Lcr.Bits.EVENPAR  = 1;
    Lcr.Bits.STICPAR  = 1;
    break;

  case MarkParity:
    Lcr.Bits.PAREN    = 1;
    Lcr.Bits.EVENPAR  = 0;
    Lcr.Bits.STICPAR  = 1;
    break;

  default:
    break;
  }

  switch (StopBits) {
  case OneStopBit:
    Lcr.Bits.STOPB = 0;
    break;

  case OneFiveStopBits:
  case TwoStopBits:
    Lcr.Bits.STOPB = 1;
    break;

  default:
    break;
  }
  //
  // DataBits
  //
  Lcr.Bits.SERIALDB = (UINT8) ((DataBits - 5) & 0x03);
  WRITE_LCR (SerialDevice->IsaIo, SerialDevice->BaseAddress, Lcr.Data);

  //
  // Set the Serial I/O mode
  //
  This->Mode->BaudRate          = BaudRate;
  This->Mode->ReceiveFifoDepth  = ReceiveFifoDepth;
  This->Mode->Timeout           = Timeout;
  This->Mode->Parity            = Parity;
  This->Mode->DataBits          = DataBits;
  This->Mode->StopBits          = StopBits;

  //
  // See if Device Path Node has actually changed
  //
  if (SerialDevice->UartDevicePath.BaudRate == BaudRate &&
      SerialDevice->UartDevicePath.DataBits == DataBits &&
      SerialDevice->UartDevicePath.Parity == Parity &&
      SerialDevice->UartDevicePath.StopBits == StopBits
      ) {
    gBS->RestoreTPL (Tpl);
    return EFI_SUCCESS;
  }
  //
  // Update the device path
  //
  SerialDevice->UartDevicePath.BaudRate = BaudRate;
  SerialDevice->UartDevicePath.DataBits = DataBits;
  SerialDevice->UartDevicePath.Parity   = (UINT8) Parity;
  SerialDevice->UartDevicePath.StopBits = (UINT8) StopBits;

  NewDevicePath = AppendDevicePathNode (
                    SerialDevice->ParentDevicePath,
                    (EFI_DEVICE_PATH_PROTOCOL *) &SerialDevice->UartDevicePath
                    );
  if (NewDevicePath == NULL) {
    gBS->RestoreTPL (Tpl);
    return EFI_DEVICE_ERROR;
  }

  if (SerialDevice->Handle != NULL) {
    Status = gBS->ReinstallProtocolInterface (
                    SerialDevice->Handle,
                    &gEfiDevicePathProtocolGuid,
                    SerialDevice->DevicePath,
                    NewDevicePath
                    );
    if (EFI_ERROR (Status)) {
      gBS->RestoreTPL (Tpl);
      return Status;
    }
  }

  if (SerialDevice->DevicePath) {
    gBS->FreePool (SerialDevice->DevicePath);
  }

  SerialDevice->DevicePath = NewDevicePath;

  gBS->RestoreTPL (Tpl);

  return EFI_SUCCESS;
}

/**
  Set Control Bits

  @param This            - Pointer to EFI_SERIAL_IO_PROTOCOL
  @param Control         - Control bits that can be settable

  @retval EFI_SUCCESS     - New Control bits were set successfully
  @retval EFI_UNSUPPORTED - The Control bits wanted to set are not supported

**/
EFI_STATUS
EFIAPI
IsaSerialSetControl (
  IN EFI_SERIAL_IO_PROTOCOL  *This,
  IN UINT32                  Control
  )
{
  SERIAL_DEV      *SerialDevice;
  SERIAL_PORT_MCR Mcr;
  EFI_TPL         Tpl;

  //
  // The control bits that can be set are :
  //     EFI_SERIAL_DATA_TERMINAL_READY: 0x0001  // WO
  //     EFI_SERIAL_REQUEST_TO_SEND: 0x0002  // WO
  //     EFI_SERIAL_HARDWARE_LOOPBACK_ENABLE: 0x1000  // RW
  //     EFI_SERIAL_SOFTWARE_LOOPBACK_ENABLE: 0x2000  // RW
  //
  SerialDevice = SERIAL_DEV_FROM_THIS (This);

  //
  // first determine the parameter is invalid
  //
  if (Control & 0xffff8ffc) {
    return EFI_UNSUPPORTED;
  }

  Tpl = gBS->RaiseTPL (TPL_NOTIFY);

  Mcr.Data = READ_MCR (SerialDevice->IsaIo, SerialDevice->BaseAddress);
  Mcr.Bits.DTRC = 0;
  Mcr.Bits.RTS = 0;
  Mcr.Bits.LME = 0;
  SerialDevice->SoftwareLoopbackEnable = FALSE;
  SerialDevice->HardwareFlowControl = FALSE;

  if (Control & EFI_SERIAL_DATA_TERMINAL_READY) {
    Mcr.Bits.DTRC = 1;
  }

  if (Control & EFI_SERIAL_REQUEST_TO_SEND) {
    Mcr.Bits.RTS = 1;
  }

  if (Control & EFI_SERIAL_HARDWARE_LOOPBACK_ENABLE) {
    Mcr.Bits.LME = 1;
  }

  if (Control & EFI_SERIAL_HARDWARE_FLOW_CONTROL_ENABLE) {
    SerialDevice->HardwareFlowControl = TRUE;
  }

  WRITE_MCR (SerialDevice->IsaIo, SerialDevice->BaseAddress, Mcr.Data);

  if (Control & EFI_SERIAL_SOFTWARE_LOOPBACK_ENABLE) {
    SerialDevice->SoftwareLoopbackEnable = TRUE;
  }

  gBS->RestoreTPL (Tpl);

  return EFI_SUCCESS;
}

/**
  Get ControlBits

  @param This        - Pointer to EFI_SERIAL_IO_PROTOCOL
  @param Control     - Control signals of the serial device

  @retval EFI_SUCCESS - Get Control signals successfully

**/
EFI_STATUS
EFIAPI
IsaSerialGetControl (
  IN EFI_SERIAL_IO_PROTOCOL  *This,
  OUT UINT32                 *Control
  )
{
  SERIAL_DEV      *SerialDevice;
  SERIAL_PORT_MSR Msr;
  SERIAL_PORT_MCR Mcr;
  EFI_TPL         Tpl;

  Tpl           = gBS->RaiseTPL (TPL_NOTIFY);

  SerialDevice  = SERIAL_DEV_FROM_THIS (This);

  *Control      = 0;

  //
  // Read the Modem Status Register
  //
  Msr.Data = READ_MSR (SerialDevice->IsaIo, SerialDevice->BaseAddress);

  if (Msr.Bits.CTS) {
    *Control |= EFI_SERIAL_CLEAR_TO_SEND;
  }

  if (Msr.Bits.DSR) {
    *Control |= EFI_SERIAL_DATA_SET_READY;
  }

  if (Msr.Bits.RI) {
    *Control |= EFI_SERIAL_RING_INDICATE;
  }

  if (Msr.Bits.DCD) {
    *Control |= EFI_SERIAL_CARRIER_DETECT;
  }
  //
  // Read the Modem Control Register
  //
  Mcr.Data = READ_MCR (SerialDevice->IsaIo, SerialDevice->BaseAddress);

  if (Mcr.Bits.DTRC) {
    *Control |= EFI_SERIAL_DATA_TERMINAL_READY;
  }

  if (Mcr.Bits.RTS) {
    *Control |= EFI_SERIAL_REQUEST_TO_SEND;
  }

  if (Mcr.Bits.LME) {
    *Control |= EFI_SERIAL_HARDWARE_LOOPBACK_ENABLE;
  }

  if (SerialDevice->HardwareFlowControl) {
    *Control |= EFI_SERIAL_HARDWARE_FLOW_CONTROL_ENABLE;
  }
  //
  // See if the Transmit FIFO is empty
  //
  IsaSerialReceiveTransmit (SerialDevice);

  if (IsaSerialFifoEmpty (&SerialDevice->Transmit)) {
    *Control |= EFI_SERIAL_OUTPUT_BUFFER_EMPTY;
  }
  //
  // See if the Receive FIFO is empty.
  //
  IsaSerialReceiveTransmit (SerialDevice);

  if (IsaSerialFifoEmpty (&SerialDevice->Receive)) {
    *Control |= EFI_SERIAL_INPUT_BUFFER_EMPTY;
  }

  if (SerialDevice->SoftwareLoopbackEnable) {
    *Control |= EFI_SERIAL_SOFTWARE_LOOPBACK_ENABLE;
  }

  gBS->RestoreTPL (Tpl);

  return EFI_SUCCESS;
}

/**
  Write the specified number of bytes to serial device

  @param This             - Pointer to EFI_SERIAL_IO_PROTOCOL
  @param  BufferSize       - On input the size of Buffer, on output the amount of
                       data actually written
  @param  Buffer           - The buffer of data to write

  @retval EFI_SUCCESS      - The data were written successfully
  @retval EFI_DEVICE_ERROR - The device reported an error
  @retval EFI_TIMEOUT      - The write operation was stopped due to timeout

**/
EFI_STATUS
EFIAPI
IsaSerialWrite (
  IN EFI_SERIAL_IO_PROTOCOL  *This,
  IN OUT UINTN               *BufferSize,
  IN VOID                    *Buffer
  )
{
  SERIAL_DEV  *SerialDevice;
  UINT8       *CharBuffer;
  UINT32      Index;
  UINTN       Elapsed;
  UINTN       ActualWrite;
  EFI_TPL     Tpl;

  SerialDevice  = SERIAL_DEV_FROM_THIS (This);
  Elapsed       = 0;
  ActualWrite   = 0;

  if (*BufferSize == 0) {
    return EFI_SUCCESS;
  }

  if (!Buffer) {
    REPORT_STATUS_CODE_WITH_DEVICE_PATH (
      EFI_ERROR_CODE,
      EFI_P_EC_OUTPUT_ERROR | EFI_PERIPHERAL_SERIAL_PORT,
      SerialDevice->DevicePath
      );

    return EFI_DEVICE_ERROR;
  }

  Tpl         = gBS->RaiseTPL (TPL_NOTIFY);

  CharBuffer  = (UINT8 *) Buffer;

  for (Index = 0; Index < *BufferSize; Index++) {
    IsaSerialFifoAdd (&SerialDevice->Transmit, CharBuffer[Index]);

    while (IsaSerialReceiveTransmit (SerialDevice) != EFI_SUCCESS || !IsaSerialFifoEmpty (&SerialDevice->Transmit)) {
      //
      //  Unsuccessful write so check if timeout has expired, if not,
      //  stall for a bit, increment time elapsed, and try again
      //
      if (Elapsed >= This->Mode->Timeout) {
        *BufferSize = ActualWrite;
        gBS->RestoreTPL (Tpl);
        return EFI_TIMEOUT;
      }

      gBS->Stall (TIMEOUT_STALL_INTERVAL);

      Elapsed += TIMEOUT_STALL_INTERVAL;
    }

    ActualWrite++;
    //
    //  Successful write so reset timeout
    //
    Elapsed = 0;
  }

  gBS->RestoreTPL (Tpl);

  return EFI_SUCCESS;
}

/**
  Read the specified number of bytes from serial device

  @param This             - Pointer to EFI_SERIAL_IO_PROTOCOL
  @param BufferSize       - On input the size of Buffer, on output the amount of
                       data returned in buffer
  @param Buffer           -  The buffer to return the data into

  @retval EFI_SUCCESS      - The data were read successfully
  @retval EFI_DEVICE_ERROR - The device reported an error
  @retval EFI_TIMEOUT      - The read operation was stopped due to timeout

**/
EFI_STATUS
EFIAPI
IsaSerialRead (
  IN EFI_SERIAL_IO_PROTOCOL  *This,
  IN OUT UINTN               *BufferSize,
  OUT VOID                   *Buffer
  )
{
  SERIAL_DEV  *SerialDevice;
  UINT32      Index;
  UINT8       *CharBuffer;
  UINTN       Elapsed;
  EFI_STATUS  Status;
  EFI_TPL     Tpl;

  SerialDevice  = SERIAL_DEV_FROM_THIS (This);
  Elapsed       = 0;

  if (*BufferSize == 0) {
    return EFI_SUCCESS;
  }

  if (!Buffer) {
    return EFI_DEVICE_ERROR;
  }

  Tpl     = gBS->RaiseTPL (TPL_NOTIFY);

  Status  = IsaSerialReceiveTransmit (SerialDevice);

  if (EFI_ERROR (Status)) {
    *BufferSize = 0;

    REPORT_STATUS_CODE_WITH_DEVICE_PATH (
      EFI_ERROR_CODE,
      EFI_P_EC_INPUT_ERROR | EFI_PERIPHERAL_SERIAL_PORT,
      SerialDevice->DevicePath
      );

    gBS->RestoreTPL (Tpl);

    return EFI_DEVICE_ERROR;
  }

  CharBuffer = (UINT8 *) Buffer;
  for (Index = 0; Index < *BufferSize; Index++) {
    while (IsaSerialFifoRemove (&SerialDevice->Receive, &(CharBuffer[Index])) != EFI_SUCCESS) {
      //
      //  Unsuccessful read so check if timeout has expired, if not,
      //  stall for a bit, increment time elapsed, and try again
      //  Need this time out to get conspliter to work.
      //
      if (Elapsed >= This->Mode->Timeout) {
        *BufferSize = Index;
        gBS->RestoreTPL (Tpl);
        return EFI_TIMEOUT;
      }

      gBS->Stall (TIMEOUT_STALL_INTERVAL);
      Elapsed += TIMEOUT_STALL_INTERVAL;

      Status = IsaSerialReceiveTransmit (SerialDevice);
      if (Status == EFI_DEVICE_ERROR) {
        *BufferSize = Index;
        gBS->RestoreTPL (Tpl);
        return EFI_DEVICE_ERROR;
      }
    }
    //
    //  Successful read so reset timeout
    //
    Elapsed = 0;
  }

  IsaSerialReceiveTransmit (SerialDevice);

  gBS->RestoreTPL (Tpl);

  return EFI_SUCCESS;
}

/**
  Use scratchpad register to test if this serial port is present

  @param SerialDevice - Pointer to serial device structure

  @return if this serial port is present
**/
BOOLEAN
IsaSerialPortPresent (
  IN SERIAL_DEV *SerialDevice
  )

{
  UINT8   Temp;
  BOOLEAN Status;

  Status = TRUE;

  //
  // Save SCR reg
  //
  Temp = READ_SCR (SerialDevice->IsaIo, SerialDevice->BaseAddress);
  WRITE_SCR (SerialDevice->IsaIo, SerialDevice->BaseAddress, 0xAA);

  if (READ_SCR (SerialDevice->IsaIo, SerialDevice->BaseAddress) != 0xAA) {
    Status = FALSE;
  }

  WRITE_SCR (SerialDevice->IsaIo, SerialDevice->BaseAddress, 0x55);

  if (READ_SCR (SerialDevice->IsaIo, SerialDevice->BaseAddress) != 0x55) {
    Status = FALSE;
  }
  //
  // Restore SCR
  //
  WRITE_SCR (SerialDevice->IsaIo, SerialDevice->BaseAddress, Temp);
  return Status;
}

/**
  Use IsaIo protocol to read serial port

  @param IsaIo       - Pointer to EFI_ISA_IO_PROTOCOL instance
  @param BaseAddress - Serial port register group base address
  @param Offset      - Offset in register group

  @return Data read from serial port

**/
UINT8
IsaSerialReadPort (
  IN EFI_ISA_IO_PROTOCOL                   *IsaIo,
  IN UINT16                                BaseAddress,
  IN UINT32                                Offset
  )
{
  UINT8 Data;

  //
  // Use IsaIo to access IO
  //
  IsaIo->Io.Read (
             IsaIo,
             EfiIsaIoWidthUint8,
             BaseAddress + Offset,
             1,
             &Data
             );
  return Data;
}

/**
  Use IsaIo protocol to write serial port

  @param  IsaIo       - Pointer to EFI_ISA_IO_PROTOCOL instance
  @param  BaseAddress - Serial port register group base address
  @param  Offset      - Offset in register group
  @param  Data        - data which is to be written to some serial port register

**/
VOID
IsaSerialWritePort (
  IN EFI_ISA_IO_PROTOCOL                 *IsaIo,
  IN UINT16                              BaseAddress,
  IN UINT32                              Offset,
  IN UINT8                               Data
  )
{
  //
  // Use IsaIo to access IO
  //
  IsaIo->Io.Write (
             IsaIo,
             EfiIsaIoWidthUint8,
             BaseAddress + Offset,
             1,
             &Data
             );
}