16550-compatible UART More...

#include <stdint.h>
#include <bits/uart.h>

Data Structures
struct	uart
	A 16550-compatible UART. More...

Macros
#define	UART_THR 0x00
	Transmitter holding register. More...

#define	UART_RBR 0x00
	Receiver buffer register. More...

#define	UART_IER 0x01
	Interrupt enable register. More...

#define	UART_FCR 0x02
	FIFO control register. More...

#define	UART_FCR_FE 0x01
	FIFO enable. More...

#define	UART_LCR 0x03
	Line control register. More...

#define	UART_LCR_WLS0 0x01
	Word length select bit 0. More...

#define	UART_LCR_WLS1 0x02
	Word length select bit 1. More...

#define	UART_LCR_STB 0x04
	Number of stop bits. More...

#define	UART_LCR_PEN 0x08
	Parity enable. More...

#define	UART_LCR_EPS 0x10
	Even parity select. More...

#define	UART_LCR_DLAB 0x80
	Divisor latch access bit. More...

#define	UART_LCR_WORD_LEN(x) ( ( (x) - 5 ) << 0 )
	Word length. More...

#define	UART_LCR_STOP_BITS(x) ( ( (x) - 1 ) << 2 )
	Stop bits. More...

#define	UART_LCR_PARITY(x) ( ( (x) - 0 ) << 3 )
	Parity. More...

#define	UART_LCR_WPS(word_len, parity, stop_bits)
	Calculate line control register value. More...

#define	UART_LCR_8N1 UART_LCR_WPS ( 8, 0, 1 )
	Default LCR value: 8 data bits, no parity, one stop bit. More...

#define	UART_MCR 0x04
	Modem control register. More...

#define	UART_MCR_DTR 0x01
	Data terminal ready. More...

#define	UART_MCR_RTS 0x02
	Request to send. More...

#define	UART_LSR 0x05
	Line status register. More...

#define	UART_LSR_DR 0x01
	Data ready. More...

#define	UART_LSR_THRE 0x20
	Transmitter holding register empty. More...

#define	UART_LSR_TEMT 0x40
	Transmitter empty. More...

#define	UART_SCR 0x07
	Scratch register. More...

#define	UART_DLL 0x00
	Divisor latch (least significant byte) More...

#define	UART_DLM 0x01
	Divisor latch (most significant byte) More...

#define	UART_MAX_BAUD 115200
	Maximum baud rate. More...

Enumerations
enum	uart_port { COM1 = 1, COM2 = 2, COM3 = 3, COM4 = 4 }
	Symbolic names for port indexes. More...

Functions
	FILE_LICENCE (GPL2_OR_LATER_OR_UBDL)

void	uart_write (struct uart *uart, unsigned int addr, uint8_t data)

uint8_t	uart_read (struct uart *uart, unsigned int addr)

int	uart_select (struct uart *uart, unsigned int port)
	Select UART port. More...

static int	uart_data_ready (struct uart *uart)
	Check if received data is ready. More...

static uint8_t	uart_receive (struct uart *uart)
	Receive data. More...

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.h.

Macro Definition Documentation

◆ UART_THR

#define UART_THR 0x00

Transmitter holding register.

Definition at line 15 of file uart.h.

◆ UART_RBR

#define UART_RBR 0x00

Receiver buffer register.

Definition at line 18 of file uart.h.

◆ UART_IER

#define UART_IER 0x01

Interrupt enable register.

Definition at line 21 of file uart.h.

◆ UART_FCR

#define UART_FCR 0x02

FIFO control register.

Definition at line 24 of file uart.h.

◆ UART_FCR_FE

#define UART_FCR_FE 0x01

FIFO enable.

Definition at line 25 of file uart.h.

◆ UART_LCR

#define UART_LCR 0x03

Line control register.

Definition at line 28 of file uart.h.

◆ UART_LCR_WLS0

#define UART_LCR_WLS0 0x01

Word length select bit 0.

Definition at line 29 of file uart.h.

◆ UART_LCR_WLS1

#define UART_LCR_WLS1 0x02

Word length select bit 1.

Definition at line 30 of file uart.h.

◆ UART_LCR_STB

#define UART_LCR_STB 0x04

Number of stop bits.

Definition at line 31 of file uart.h.

◆ UART_LCR_PEN

#define UART_LCR_PEN 0x08

Parity enable.

Definition at line 32 of file uart.h.

◆ UART_LCR_EPS

#define UART_LCR_EPS 0x10

Even parity select.

Definition at line 33 of file uart.h.

◆ UART_LCR_DLAB

#define UART_LCR_DLAB 0x80

Divisor latch access bit.

Definition at line 34 of file uart.h.

◆ UART_LCR_WORD_LEN

#define UART_LCR_WORD_LEN ( x ) ( ( (x) - 5 ) << 0 )

Word length.

Definition at line 36 of file uart.h.

◆ UART_LCR_STOP_BITS

#define UART_LCR_STOP_BITS ( x ) ( ( (x) - 1 ) << 2 )

Stop bits.

Definition at line 37 of file uart.h.

◆ UART_LCR_PARITY

#define UART_LCR_PARITY ( x ) ( ( (x) - 0 ) << 3 )

Parity.

Definition at line 38 of file uart.h.

◆ UART_LCR_WPS

#define UART_LCR_WPS	(	word_len,
		parity,
		stop_bits
	)

Value:

( UART_LCR_WORD_LEN ( (word_len) ) |            \
          UART_LCR_PARITY ( (parity) ) |                \
          UART_LCR_STOP_BITS ( (stop_bits) ) )

Calculate line control register value.

Parameters

word_len	Word length (5-8)
parity	Parity (0=none, 1=odd, 3=even)
stop_bits	Stop bits (1-2)

Return values

lcr	Line control register value

Definition at line 48 of file uart.h.

◆ UART_LCR_8N1

#define UART_LCR_8N1 UART_LCR_WPS ( 8, 0, 1 )

Default LCR value: 8 data bits, no parity, one stop bit.

Definition at line 54 of file uart.h.

◆ UART_MCR

#define UART_MCR 0x04

Modem control register.

Definition at line 57 of file uart.h.

◆ UART_MCR_DTR

#define UART_MCR_DTR 0x01

Data terminal ready.

Definition at line 58 of file uart.h.

◆ UART_MCR_RTS

#define UART_MCR_RTS 0x02

Request to send.

Definition at line 59 of file uart.h.

◆ UART_LSR

#define UART_LSR 0x05

Line status register.

Definition at line 62 of file uart.h.

◆ UART_LSR_DR

#define UART_LSR_DR 0x01

Data ready.

Definition at line 63 of file uart.h.

◆ UART_LSR_THRE

#define UART_LSR_THRE 0x20

Transmitter holding register empty.

Definition at line 64 of file uart.h.

◆ UART_LSR_TEMT

#define UART_LSR_TEMT 0x40

Transmitter empty.

Definition at line 65 of file uart.h.

◆ UART_SCR

#define UART_SCR 0x07

Scratch register.

Definition at line 68 of file uart.h.

◆ UART_DLL

#define UART_DLL 0x00

Divisor latch (least significant byte)

Definition at line 71 of file uart.h.

◆ UART_DLM

#define UART_DLM 0x01

Divisor latch (most significant byte)

Definition at line 74 of file uart.h.

◆ UART_MAX_BAUD

#define UART_MAX_BAUD 115200

Maximum baud rate.

Definition at line 77 of file uart.h.

Enumeration Type Documentation

◆ uart_port

enum uart_port

Symbolic names for port indexes.

Enumerator
COM1
COM2
COM3
COM4

Definition at line 90 of file uart.h.

                {
         COM1 = 1,
         COM2 = 2,
         COM3 = 3,
         COM4 = 4,
 };

Function Documentation

◆ FILE_LICENCE()

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL )

◆ uart_write()

void uart_write	(	struct uart *	uart,
		unsigned int	addr,
		uint8_t	data
	)

Referenced by uart_exists(), uart_init(), and uart_transmit().

◆ uart_read()

uint8_t uart_read	(	struct uart *	uart,
		unsigned int	addr
	)

Referenced by uart_data_ready(), uart_exists(), uart_flush(), uart_init(), uart_receive(), and uart_transmit().

◆ uart_select()

int uart_select	(	struct uart *	uart,
		unsigned int	port
	)

Select UART port.

Parameters

uart	UART
port	Port number, or 0 to disable

Return values

rc	Return status code

Definition at line 50 of file x86_uart.c.

                                                          {
         int rc;
 
         /* Set new UART base */
         if ( port >= ( sizeof ( uart_base ) / sizeof ( uart_base[0] ) ) ) {
                 rc = -ENODEV;
                 goto err;
         }
         uart->base = ( ( void * ) ( intptr_t ) uart_base[port] );
 
         /* Check that UART exists */
         if ( ( rc = uart_exists ( uart ) ) != 0 )
                 goto err;
 
         return 0;
 
  err:
         uart->base = NULL;
         return rc;
 }

References uart::base, ENODEV, NULL, port, rc, uart_base, and uart_exists().

Referenced by gdbserial_configure(), and serial_init().

◆ uart_data_ready()

static int uart_data_ready ( struct uart * uart )

inlinestatic

Check if received data is ready.

Parameters

uart UART

Return values

ready Data is ready

Definition at line 109 of file uart.h.

                                                         {
         uint8_t lsr;
 
         lsr = uart_read ( uart, UART_LSR );
         return ( lsr & UART_LSR_DR );
 }

References UART_LSR, UART_LSR_DR, and uart_read().

Referenced by gdbserial_recv(), serial_getchar(), and serial_iskey().

◆ uart_receive()

static uint8_t uart_receive ( struct uart * uart )

inlinestatic

Receive data.

Parameters

uart UART

Return values

data Data

Definition at line 122 of file uart.h.

                                                          {
 
         return uart_read ( uart, UART_RBR );
 }

References UART_RBR, and uart_read().

Referenced by gdbserial_recv(), and serial_getchar().

◆ 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().

Data Structures

Macros

Enumerations

Functions

Detailed Description

Macro Definition Documentation

◆ UART_THR

◆ UART_RBR

◆ UART_IER

◆ UART_FCR

◆ UART_FCR_FE

◆ UART_LCR

◆ UART_LCR_WLS0

◆ UART_LCR_WLS1

◆ UART_LCR_STB

◆ UART_LCR_PEN

◆ UART_LCR_EPS

◆ UART_LCR_DLAB

◆ UART_LCR_WORD_LEN

◆ UART_LCR_STOP_BITS

◆ UART_LCR_PARITY

◆ UART_LCR_WPS

◆ UART_LCR_8N1

◆ UART_MCR

◆ UART_MCR_DTR

◆ UART_MCR_RTS

◆ UART_LSR

◆ UART_LSR_DR

◆ UART_LSR_THRE

◆ UART_LSR_TEMT

◆ UART_SCR

◆ UART_DLL

◆ UART_DLM

◆ UART_MAX_BAUD

Enumeration Type Documentation

◆ uart_port

Function Documentation

◆ FILE_LICENCE()

◆ uart_write()

◆ uart_read()

◆ uart_select()

◆ uart_data_ready()

◆ uart_receive()

◆ uart_transmit()

◆ uart_flush()

◆ uart_exists()

◆ uart_init()