bcm2835.c File Reference

#include "common.h"

Macros
#define	AUX_MU_IO_REG   0x40
#define	AUX_MU_IER_REG   0x44
#define	AUX_MU_LCR_REG   0x4C
#define	AUX_MU_STAT_REG   0x64
#define	AUX_MU_IER_TXE   0x00000001
#define	AUX_MU_IER_RXNE   0x00000002
#define	AUX_MU_LCR_8BIT   0x00000003
#define	AUX_MU_STAT_RXNE   0x00000001
#define	AUX_MU_STAT_TXNF   0x00000002

Functions
BOOLEAN	Bcm2835RxReady (_Inout_ PCPPORT Port)
BOOLEAN	Bcm2835InitializePort (_In_opt_ _Null_terminated_ PCHAR LoadOptions, _Inout_ PCPPORT Port, BOOLEAN MemoryMapped, UCHAR AccessSize, UCHAR BitWidth)
BOOLEAN	Bcm2835SetBaud (_Inout_ PCPPORT Port, ULONG Rate)
UART_STATUS	Bcm2835GetByte (_Inout_ PCPPORT Port, _Out_ PUCHAR Byte)
UART_STATUS	Bcm2835PutByte (_Inout_ PCPPORT Port, UCHAR Byte, BOOLEAN BusyWait)

Variables
UART_HARDWARE_DRIVER	Bcm2835HardwareDriver

Macro Definition Documentation

AUX_MU_IER_REG

#define AUX_MU_IER_REG   0x44

AUX_MU_IER_RXNE

#define AUX_MU_IER_RXNE   0x00000002

AUX_MU_IER_TXE

#define AUX_MU_IER_TXE   0x00000001

AUX_MU_IO_REG

#define AUX_MU_IO_REG   0x40

AUX_MU_LCR_8BIT

#define AUX_MU_LCR_8BIT   0x00000003

AUX_MU_LCR_REG

#define AUX_MU_LCR_REG   0x4C

AUX_MU_STAT_REG

#define AUX_MU_STAT_REG   0x64

AUX_MU_STAT_RXNE

#define AUX_MU_STAT_RXNE   0x00000001

AUX_MU_STAT_TXNF

#define AUX_MU_STAT_TXNF   0x00000002

Function Documentation

Bcm2835GetByte()

UART_STATUS Bcm2835GetByte	(	_Inout_ PCPPORT	Port,
		_Out_ PUCHAR	Byte )

{
    ULONG Value;
 
    if ((Port == NULL) || (Port->Address == NULL))
    {
        return UartNotReady;
    }
 
    //
    // Check to see if a byte is available.
    //
 
    if (Bcm2835RxReady(Port) != FALSE)
    {
        //
        // Fetch the data byte and associated error information.
        //
 
        Value = READ_REGISTER_ULONG((PULONG)(Port->Address + AUX_MU_IO_REG));
 
        //
        // Cannot check for errors as the mini UART does not provide this
        // information.
        //
 
        *Byte = Value & (UCHAR)0xFF;
        return UartSuccess;
    }
 
    return UartNoData;
}

Bcm2835InitializePort()

BOOLEAN Bcm2835InitializePort	(	_In_opt_ _Null_terminated_ PCHAR	LoadOptions,
		_Inout_ PCPPORT	Port,
		BOOLEAN	MemoryMapped,
		UCHAR	AccessSize,
		UCHAR	BitWidth )

{
    UNREFERENCED_PARAMETER(LoadOptions);
    UNREFERENCED_PARAMETER(AccessSize);
    UNREFERENCED_PARAMETER(BitWidth);
 
    ULONG IntEnable;
 
    if (MemoryMapped == FALSE)
    {
        return FALSE;
    }
 
    Port->Flags = 0;
 
    //
    // We cannot set the baud rate since we do not have the UART's clock value.
    // Moreover with Raspberry Pi 2 and 3, the UEFI firmware sets the baud rate
    // to 921600 bps, while BCDEdit limits it to 115200 bps.
    //
 
    Port->BaudRate = 0;
 
    //
    // Disable interrupts
    //
 
    IntEnable = READ_REGISTER_ULONG((PULONG)(Port->Address + AUX_MU_IER_REG));
    IntEnable &= ~(AUX_MU_IER_TXE | AUX_MU_IER_RXNE);
    WRITE_REGISTER_ULONG((PULONG)(Port->Address + AUX_MU_IER_REG), IntEnable);
 
    //
    // Set 8 bit mode
    //
 
    WRITE_REGISTER_ULONG((PULONG)(Port->Address + AUX_MU_LCR_REG),
                         AUX_MU_LCR_8BIT);
 
    //
    // Mini UART RX/TX are always enabled!
    //
 
    return TRUE;
}

Bcm2835PutByte()

UART_STATUS Bcm2835PutByte	(	_Inout_ PCPPORT	Port,
		UCHAR	Byte,
		BOOLEAN	BusyWait )

{
    ULONG StatusReg;
 
    if ((Port == NULL) || (Port->Address == NULL))
    {
        return UartNotReady;
    }
 
    //
    // If BusyWait is set, wait for FIFO to be not full. Otherwise, only check
    // one time.
    //
 
    if (BusyWait != FALSE)
    {
        do
        {
            StatusReg =
                READ_REGISTER_ULONG((PULONG)(Port->Address + AUX_MU_STAT_REG));
 
        } while ((StatusReg & AUX_MU_STAT_TXNF) == 0);
    }
    else
    {
        StatusReg =
            READ_REGISTER_ULONG((PULONG)(Port->Address + AUX_MU_STAT_REG));
 
        if ((StatusReg & AUX_MU_STAT_TXNF) == 0)
        {
            return UartNotReady;
        }
    }
 
    //
    // Send the byte
    //
 
    WRITE_REGISTER_ULONG((PULONG)(Port->Address + AUX_MU_IO_REG), (ULONG)Byte);
    return UartSuccess;
}

Bcm2835RxReady()

BOOLEAN Bcm2835RxReady

(

_Inout_ PCPPORT

Port

)

{
    ULONG StatusReg;
 
    if ((Port == NULL) || (Port->Address == NULL))
    {
        return FALSE;
    }
 
    //
    // Read the Flag Register to determine if there is any pending
    // data to read.
    //
 
    StatusReg = READ_REGISTER_ULONG((PULONG)(Port->Address + AUX_MU_STAT_REG));
 
    //
    // Check the "receive FIFO not-empty" flag.  If it is set, then at least
    // one byte is available.
    //
 
    if ((StatusReg & AUX_MU_STAT_RXNE) != 0)
    {
        return TRUE;
    }
 
    return FALSE;
}

Bcm2835SetBaud()

BOOLEAN Bcm2835SetBaud	(	_Inout_ PCPPORT	Port,
		ULONG	Rate )

{
    if ((Port == NULL) || (Port->Address == NULL))
    {
        return FALSE;
    }
 
    //
    // Remember the baud rate.
    //
 
    Port->BaudRate = Rate;
    return TRUE;
}

Variable Documentation

Bcm2835HardwareDriver

UART_HARDWARE_DRIVER Bcm2835HardwareDriver

Initial value:

= {
    Bcm2835InitializePort,
    Bcm2835SetBaud,
    Bcm2835GetByte,
    Bcm2835PutByte,
    Bcm2835RxReady}

                                             {
    Bcm2835InitializePort,
    Bcm2835SetBaud,
    Bcm2835GetByte,
    Bcm2835PutByte,
    Bcm2835RxReady};