ns16550.c File Reference

16550-compatible UART More...

#include <unistd.h>
#include <errno.h>
#include <ipxe/uart.h>
#include <ipxe/ns16550.h>

Go to the source code of this file.

Macros
#define	NS16550_THRE_TIMEOUT_MS   100
	Timeout for transmit holding register to become empty. More...
#define	NS16550_TEMT_TIMEOUT_MS   1000
	Timeout for transmitter to become empty. More...

Functions
	FILE_LICENCE (GPL2_OR_LATER_OR_UBDL)
static void	ns16550_transmit (struct uart *uart, uint8_t data)
	Transmit data. More...
static int	ns16550_data_ready (struct uart *uart)
	Check if data is ready. More...
static uint8_t	ns16550_receive (struct uart *uart)
	Receive data. More...
static void	ns16550_flush (struct uart *uart)
	Flush transmitted data. More...
static int	ns16550_init (struct uart *uart)
	Initialise UART. More...

Variables
struct uart_operations	ns16550_operations
	16550 UART operations More...

Detailed Description

16550-compatible UART

Definition in file ns16550.c.

Macro Definition Documentation

NS16550_THRE_TIMEOUT_MS

#define NS16550_THRE_TIMEOUT_MS   100

Timeout for transmit holding register to become empty.

Definition at line 38 of file ns16550.c.

NS16550_TEMT_TIMEOUT_MS

#define NS16550_TEMT_TIMEOUT_MS   1000

Timeout for transmitter to become empty.

Definition at line 41 of file ns16550.c.

Function Documentation

FILE_LICENCE()

FILE_LICENCE

(

GPL2_OR_LATER_OR_UBDL

)

ns16550_transmit()

static void ns16550_transmit ( struct uart *  uart, uint8_t  data  )

static

Transmit data.

Parameters

uart	UART
data	Data

Definition at line 49 of file ns16550.c.

                                                                 {
        struct ns16550_uart *ns16550 = uart->priv;
        unsigned int i;
        uint8_t lsr;

        /* Wait for transmitter holding register to become empty */
        for ( i = 0 ; i < NS16550_THRE_TIMEOUT_MS ; i++ ) {
                lsr = ns16550_read ( ns16550, NS16550_LSR );
                if ( lsr & NS16550_LSR_THRE )
                        break;
                mdelay ( 1 );
        }

        /* Transmit data (even if we timed out) */
        ns16550_write ( ns16550, NS16550_THR, data );
}

References data, mdelay(), NS16550_LSR, NS16550_LSR_THRE, ns16550_read(), NS16550_THR, NS16550_THRE_TIMEOUT_MS, ns16550_write(), and uart::priv.

ns16550_data_ready()

static int ns16550_data_ready ( struct uart *  uart )

static

Check if data is ready.

Parameters

uart

UART

Return values

ready

Data is ready

Definition at line 72 of file ns16550.c.

                                                    {
        struct ns16550_uart *ns16550 = uart->priv;
        uint8_t lsr;

        /* Check for receive data ready */
        lsr = ns16550_read ( ns16550, NS16550_LSR );
        return ( lsr & NS16550_LSR_DR );
}

References NS16550_LSR, NS16550_LSR_DR, ns16550_read(), and uart::priv.

Referenced by ns16550_init().

ns16550_receive()

static uint8_t ns16550_receive ( struct uart *  uart )

static

Receive data.

Parameters

uart

UART

Return values

data

Data

Definition at line 87 of file ns16550.c.

                                                     {
        struct ns16550_uart *ns16550 = uart->priv;
        uint8_t rbr;

        /* Receive byte */
        rbr = ns16550_read ( ns16550, NS16550_RBR );
        return rbr;
}

References NS16550_RBR, ns16550_read(), and uart::priv.

Referenced by ns16550_init().

ns16550_flush()

static void ns16550_flush ( struct uart *  uart )

static

Flush transmitted data.

Parameters

uart

UART

Definition at line 101 of file ns16550.c.

                                                {
        struct ns16550_uart *ns16550 = uart->priv;
        unsigned int i;
        uint8_t lsr;

        /* Wait for transmitter to become empty */
        for ( i = 0 ; i < NS16550_TEMT_TIMEOUT_MS ; i++ ) {
                lsr = ns16550_read ( ns16550, NS16550_LSR );
                if ( lsr & NS16550_LSR_TEMT )
                        break;
        }
}

References NS16550_LSR, NS16550_LSR_TEMT, ns16550_read(), NS16550_TEMT_TIMEOUT_MS, and uart::priv.

Referenced by ns16550_init().

ns16550_init()

static int ns16550_init ( struct uart *  uart )

static

Initialise UART.

Parameters

uart

UART

Return values

rc	Return status code

Definition at line 120 of file ns16550.c.

                                              {
        struct ns16550_uart *ns16550 = uart->priv;
        uint8_t dlm;
        uint8_t dll;

        /* Fail if UART scratch register seems not to be present */
        ns16550_write ( ns16550, NS16550_SCR, 0x18 );
        if ( ns16550_read ( ns16550, NS16550_SCR ) != 0x18 )
                return -ENODEV;
        ns16550_write ( ns16550, NS16550_SCR, 0xae );
        if ( ns16550_read ( ns16550, NS16550_SCR ) != 0xae )
                return -ENODEV;

        /* Wait for UART to become idle before modifying LCR */
        ns16550_flush ( uart );

        /* Configure divisor and line control register, if applicable */
        ns16550_write ( ns16550, NS16550_LCR,
                        ( NS16550_LCR_8N1 | NS16550_LCR_DLAB ) );
        if ( uart->baud ) {
                ns16550->divisor = ( ( ns16550->clock / uart->baud ) /
                                     NS16550_CLK_BIT );
                dlm = ( ( ns16550->divisor >> 8 ) & 0xff );
                dll = ( ( ns16550->divisor >> 0 ) & 0xff );
                ns16550_write ( ns16550, NS16550_DLM, dlm );
                ns16550_write ( ns16550, NS16550_DLL, dll );
        } else {
                dlm = ns16550_read ( ns16550, NS16550_DLM );
                dll = ns16550_read ( ns16550, NS16550_DLL );
                ns16550->divisor = ( ( dlm << 8 ) | dll );
        }
        ns16550_write ( ns16550, NS16550_LCR, NS16550_LCR_8N1 );

        /* Disable interrupts */
        ns16550_write ( ns16550, NS16550_IER, 0 );

        /* Enable FIFOs */
        ns16550_write ( ns16550, NS16550_FCR, NS16550_FCR_FE );

        /* Assert DTR and RTS */
        ns16550_write ( ns16550, NS16550_MCR,
                        ( NS16550_MCR_DTR | NS16550_MCR_RTS ) );

        /* Flush any stale received data */
        while ( ns16550_data_ready ( uart ) )
                ns16550_receive ( uart );

        return 0;
}

References uart::baud, ns16550_uart::clock, ns16550_uart::divisor, ENODEV, NS16550_CLK_BIT, ns16550_data_ready(), NS16550_DLL, NS16550_DLM, NS16550_FCR, NS16550_FCR_FE, ns16550_flush(), NS16550_IER, NS16550_LCR, NS16550_LCR_8N1, NS16550_LCR_DLAB, NS16550_MCR, NS16550_MCR_DTR, NS16550_MCR_RTS, ns16550_read(), ns16550_receive(), NS16550_SCR, ns16550_write(), and uart::priv.

Variable Documentation

ns16550_operations

struct uart_operations ns16550_operations

Initial value:

= {
        .transmit = ns16550_transmit,
        .data_ready = ns16550_data_ready,
        .receive = ns16550_receive,
        .init = ns16550_init,
        .flush = ns16550_flush,
}

16550 UART operations

Definition at line 171 of file ns16550.c.

Referenced by dwuart_probe(), and spcr_16550().