uart.c File Reference

16550-compatible UART More...

#include <unistd.h>
#include <errno.h>
#include <ipxe/uart.h>

Go to the source code of this file.

Macros
#define	UART_THRE_TIMEOUT_MS   100
	Timeout for transmit holding register to become empty. More...
#define	UART_TEMT_TIMEOUT_MS   1000
	Timeout for transmitter to become empty. More...

Functions
	FILE_LICENCE (GPL2_OR_LATER_OR_UBDL)
void	uart_transmit (struct uart *uart, uint8_t data)
	Transmit data. More...
void	uart_flush (struct uart *uart)
	Flush data. More...
int	uart_exists (struct uart *uart)
	Check for existence of UART. More...
int	uart_init (struct uart *uart, unsigned int baud, uint8_t lcr)
	Initialise UART. More...

Detailed Description

16550-compatible UART

Definition in file uart.c.

Macro Definition Documentation

UART_THRE_TIMEOUT_MS

#define UART_THRE_TIMEOUT_MS   100

Timeout for transmit holding register to become empty.

Definition at line 37 of file uart.c.

UART_TEMT_TIMEOUT_MS

#define UART_TEMT_TIMEOUT_MS   1000

Timeout for transmitter to become empty.

Definition at line 40 of file uart.c.

Function Documentation

FILE_LICENCE()

FILE_LICENCE

(

GPL2_OR_LATER_OR_UBDL

)

uart_transmit()

void uart_transmit	(	struct uart *	uart,
		uint8_t	data
	)

Transmit data.

Parameters

uart	UART
data	Data

Definition at line 48 of file uart.c.

                                                       {
        unsigned int i;
        uint8_t lsr;

        /* Wait for transmitter holding register to become empty */
        for ( i = 0 ; i < UART_THRE_TIMEOUT_MS ; i++ ) {
                lsr = uart_read ( uart, UART_LSR );
                if ( lsr & UART_LSR_THRE )
                        break;
                mdelay ( 1 );
        }

        /* Transmit data (even if we timed out) */
        uart_write ( uart, UART_THR, data );
}

References data, mdelay(), UART_LSR, UART_LSR_THRE, uart_read(), UART_THR, UART_THRE_TIMEOUT_MS, and uart_write().

Referenced by gdbserial_send(), int21(), and serial_putchar().

uart_flush()

void uart_flush

(

struct uart *

uart

)

Flush data.

Parameters

uart

UART

Definition at line 69 of file uart.c.

                                      {
        unsigned int i;
        uint8_t lsr;

        /* Wait for transmitter and receiver to become empty */
        for ( i = 0 ; i < UART_TEMT_TIMEOUT_MS ; i++ ) {
                uart_read ( uart, UART_RBR );
                lsr = uart_read ( uart, UART_LSR );
                if ( ( lsr & UART_LSR_TEMT ) && ! ( lsr & UART_LSR_DR ) )
                        break;
        }
}

References UART_LSR, UART_LSR_DR, UART_LSR_TEMT, UART_RBR, uart_read(), and UART_TEMT_TIMEOUT_MS.

Referenced by serial_shutdown(), and uart_init().

uart_exists()

int uart_exists

(

struct uart *

uart

)

Check for existence of UART.

Parameters

uart

UART

Return values

rc	Return status code

Definition at line 88 of file uart.c.

                                      {

        /* Fail if no UART port is defined */
        if ( ! uart->base )
                return -ENODEV;

        /* Fail if UART scratch register seems not to be present */
        uart_write ( uart, UART_SCR, 0x18 );
        if ( uart_read ( uart, UART_SCR ) != 0x18 )
                return -ENODEV;
        uart_write ( uart, UART_SCR, 0xae );
        if ( uart_read ( uart, UART_SCR ) != 0xae )
                return -ENODEV;

        return 0;
}

References uart::base, ENODEV, uart_read(), UART_SCR, and uart_write().

Referenced by uart_init(), and uart_select().

uart_init()

int uart_init	(	struct uart *	uart,
		unsigned int	baud,
		uint8_t	lcr
	)

Initialise UART.

Parameters

uart	UART
baud	Baud rate, or zero to leave unchanged
lcr	Line control register value, or zero to leave unchanged

Return values

rc	Return status code

Definition at line 113 of file uart.c.

                                                                    {
        uint8_t dlm;
        uint8_t dll;
        int rc;

        /* Check for existence of UART */
        if ( ( rc = uart_exists ( uart ) ) != 0 )
                return rc;

        /* Configure divisor and line control register, if applicable */
        if ( ! lcr )
                lcr = uart_read ( uart, UART_LCR );
        uart->lcr = lcr;
        uart_write ( uart, UART_LCR, ( lcr | UART_LCR_DLAB ) );
        if ( baud ) {
                uart->divisor = ( UART_MAX_BAUD / baud );
                dlm = ( ( uart->divisor >> 8 ) & 0xff );
                dll = ( ( uart->divisor >> 0 ) & 0xff );
                uart_write ( uart, UART_DLM, dlm );
                uart_write ( uart, UART_DLL, dll );
        } else {
                dlm = uart_read ( uart, UART_DLM );
                dll = uart_read ( uart, UART_DLL );
                uart->divisor = ( ( dlm << 8 ) | dll );
        }
        uart_write ( uart, UART_LCR, ( lcr & ~UART_LCR_DLAB ) );

        /* Disable interrupts */
        uart_write ( uart, UART_IER, 0 );

        /* Enable FIFOs */
        uart_write ( uart, UART_FCR, UART_FCR_FE );

        /* Assert DTR and RTS */
        uart_write ( uart, UART_MCR, ( UART_MCR_DTR | UART_MCR_RTS ) );

        /* Flush any stale data */
        uart_flush ( uart );

        return 0;
}

References uart::divisor, uart::lcr, rc, UART_DLL, UART_DLM, uart_exists(), UART_FCR, UART_FCR_FE, uart_flush(), UART_IER, UART_LCR, UART_LCR_DLAB, UART_MAX_BAUD, UART_MCR, UART_MCR_DTR, UART_MCR_RTS, uart_read(), and uart_write().

Referenced by gdbserial_configure(), and serial_init().