[serial] Add general abstraction of a 16550-compatible UART

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/x86/core/x86_uart.c

@@ -0,0 +1,62 @@
+/*
+ * Copyright (C) 2014 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ * You can also choose to distribute this program under the terms of
+ * the Unmodified Binary Distribution Licence (as given in the file
+ * COPYING.UBDL), provided that you have satisfied its requirements.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+/** @file
+ *
+ * 16550-compatible UART
+ *
+ */
+
+#include <errno.h>
+#include <ipxe/uart.h>
+
+/** UART port bases */
+static uint16_t uart_base[] = {
+	[COM1] = 0x3f8,
+	[COM2] = 0x2f8,
+	[COM3] = 0x3e8,
+	[COM4] = 0x2e8,
+};
+
+/**
+ * Select UART port
+ *
+ * @v uart		UART
+ * @v port		Port number, or 0 to disable
+ * @ret rc		Return status code
+ */
+int uart_select ( struct uart *uart, unsigned int port ) {
+
+	/* Clear UART base */
+	uart->base = NULL;
+
+	/* Set new UART base */
+	if ( port < ( sizeof ( uart_base ) / sizeof ( uart_base[0] ) ) ) {
+		uart->base = ( ( void * ) ( intptr_t ) uart_base[port] );
+		return 0;
+	} else {
+		return -ENODEV;
+	}
+}

src/arch/x86/include/bits/errfile.h

@@ -48,6 +48,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define ERRFILE_timer_bios    ( ERRFILE_ARCH | ERRFILE_DRIVER | 0x00010000 )
 #define ERRFILE_hvm	      ( ERRFILE_ARCH | ERRFILE_DRIVER | 0x00020000 )
 #define ERRFILE_hyperv	      ( ERRFILE_ARCH | ERRFILE_DRIVER | 0x00030000 )
+#define ERRFILE_x86_uart      ( ERRFILE_ARCH | ERRFILE_DRIVER | 0x00040000 )
 
 #define ERRFILE_cpuid_cmd      ( ERRFILE_ARCH | ERRFILE_OTHER | 0x00000000 )
 #define ERRFILE_cpuid_settings ( ERRFILE_ARCH | ERRFILE_OTHER | 0x00010000 )

src/arch/x86/include/bits/uart.h

@@ -0,0 +1,41 @@
+#ifndef _BITS_UART_H
+#define _BITS_UART_H
+
+/** @file
+ *
+ * 16550-compatible UART
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <stdint.h>
+#include <ipxe/io.h>
+
+/**
+ * Write to UART register
+ *
+ * @v uart		UART
+ * @v addr		Register address
+ * @v data		Data
+ */
+static inline __attribute__ (( always_inline )) void
+uart_write ( struct uart *uart, unsigned int addr, uint8_t data ) {
+	outb ( data, ( uart->base + addr ) );
+}
+
+/**
+ * Read from UART register
+ *
+ * @v uart		UART
+ * @v addr		Register address
+ * @ret data		Data
+ */
+static inline __attribute__ (( always_inline )) uint8_t
+uart_read ( struct uart *uart, unsigned int addr ) {
+	return inb ( uart->base + addr );
+}
+
+extern int uart_select ( struct uart *uart, unsigned int port );
+
+#endif /* _BITS_UART_H */

src/core/uart.c

@@ -0,0 +1,135 @@
+/*
+ * Copyright (C) 2014 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ * You can also choose to distribute this program under the terms of
+ * the Unmodified Binary Distribution Licence (as given in the file
+ * COPYING.UBDL), provided that you have satisfied its requirements.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+/** @file
+ *
+ * 16550-compatible UART
+ *
+ */
+
+#include <unistd.h>
+#include <errno.h>
+#include <ipxe/uart.h>
+
+/** Timeout for transmit holding register to become empty */
+#define UART_THRE_TIMEOUT_MS 100
+
+/** Timeout for transmitter to become empty */
+#define UART_TEMT_TIMEOUT_MS 1000
+
+/**
+ * Transmit data
+ *
+ * @v uart		UART
+ * @v data		Data
+ */
+void uart_transmit ( struct uart *uart, uint8_t data ) {
+	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 );
+}
+
+/**
+ * Flush data
+ *
+ * @v uart		UART
+ */
+void uart_flush ( struct uart *uart ) {
+	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;
+	}
+}
+
+/**
+ * Initialise UART
+ *
+ * @v uart		UART
+ * @v baud		Baud rate, or zero to leave unchanged
+ * @v lcr		Line control register value, or zero to leave unchanged
+ * @ret rc		Return status code
+ */
+int uart_init ( struct uart *uart, unsigned int baud, uint8_t lcr ) {
+	uint8_t dlm;
+	uint8_t dll;
+
+	/* Check for existence of UART */
+	if ( ! uart->base )
+		return -ENODEV;
+	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;
+
+	/* 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;
+}

src/include/ipxe/errfile.h

@@ -89,6 +89,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define ERRFILE_i2c_bit		     ( ERRFILE_DRIVER | 0x00120000 )
 #define ERRFILE_spi_bit		     ( ERRFILE_DRIVER | 0x00130000 )
 #define ERRFILE_nvsvpd		     ( ERRFILE_DRIVER | 0x00140000 )
+#define ERRFILE_uart		     ( ERRFILE_DRIVER | 0x00150000 )
 
 #define ERRFILE_3c509		     ( ERRFILE_DRIVER | 0x00200000 )
 #define ERRFILE_bnx2		     ( ERRFILE_DRIVER | 0x00210000 )

src/include/ipxe/uart.h

@@ -0,0 +1,131 @@
+#ifndef _IPXE_UART_H
+#define _IPXE_UART_H
+
+/** @file
+ *
+ * 16550-compatible UART
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <stdint.h>
+
+/** Transmitter holding register */
+#define UART_THR 0x00
+
+/** Receiver buffer register */
+#define UART_RBR 0x00
+
+/** Interrupt enable register */
+#define UART_IER 0x01
+
+/** FIFO control register */
+#define UART_FCR 0x02
+#define UART_FCR_FE	0x01	/**< FIFO enable */
+
+/** Line control register */
+#define UART_LCR 0x03
+#define UART_LCR_WLS0	0x01	/**< Word length select bit 0 */
+#define UART_LCR_WLS1	0x02	/**< Word length select bit 1 */
+#define UART_LCR_STB	0x04	/**< Number of stop bits */
+#define UART_LCR_PEN	0x08	/**< Parity enable */
+#define UART_LCR_EPS	0x10	/**< Even parity select */
+#define UART_LCR_DLAB	0x80	/**< Divisor latch access bit */
+
+#define UART_LCR_WORD_LEN(x)	( ( (x) - 5 ) << 0 )	/**< Word length */
+#define UART_LCR_STOP_BITS(x)	( ( (x) - 1 ) << 2 )	/**< Stop bits */
+#define UART_LCR_PARITY(x)	( ( (x) - 0 ) << 3 )	/**< Parity */
+
+/**
+ * Calculate line control register value
+ *
+ * @v word_len		Word length (5-8)
+ * @v parity		Parity (0=none, 1=odd, 3=even)
+ * @v stop_bits		Stop bits (1-2)
+ * @ret lcr		Line control register value
+ */
+#define UART_LCR_WPS( word_len, parity, stop_bits )	\
+	( UART_LCR_WORD_LEN ( (word_len) ) |		\
+	  UART_LCR_PARITY ( (parity) ) |		\
+	  UART_LCR_STOP_BITS ( (stop_bits) ) )
+
+/** Default LCR value: 8 data bits, no parity, one stop bit */
+#define UART_LCR_8N1 UART_LCR_WPS ( 8, 0, 1 )
+
+/** Modem control register */
+#define UART_MCR 0x04
+#define UART_MCR_DTR	0x01	/**< Data terminal ready */
+#define UART_MCR_RTS	0x02	/**< Request to send */
+
+/** Line status register */
+#define UART_LSR 0x05
+#define UART_LSR_DR	0x01	/**< Data ready */
+#define UART_LSR_THRE	0x20	/**< Transmitter holding register empty */
+#define UART_LSR_TEMT	0x40	/**< Transmitter empty */
+
+/** Scratch register */
+#define UART_SCR 0x07
+
+/** Divisor latch (least significant byte) */
+#define UART_DLL 0x00
+
+/** Divisor latch (most significant byte) */
+#define UART_DLM 0x01
+
+/** Maximum baud rate */
+#define UART_MAX_BAUD 115200
+
+/** A 16550-compatible UART */
+struct uart {
+	/** I/O port base address */
+	void *base;
+	/** Baud rate divisor */
+	uint16_t divisor;
+	/** Line control register */
+	uint8_t lcr;
+};
+
+/** Symbolic names for port indexes */
+enum uart_port {
+	COM1 = 1,
+	COM2 = 2,
+	COM3 = 3,
+	COM4 = 4,
+};
+
+#include <bits/uart.h>
+
+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 );
+
+/**
+ * Check if received data is ready
+ *
+ * @v uart		UART
+ * @ret ready		Data is ready
+ */
+static inline int uart_data_ready ( struct uart *uart ) {
+	uint8_t lsr;
+
+	lsr = uart_read ( uart, UART_LSR );
+	return ( lsr & UART_LSR_DR );
+}
+
+/**
+ * Receive data
+ *
+ * @v uart		UART
+ * @ret data		Data
+ */
+static inline uint8_t uart_receive ( struct uart *uart ) {
+
+	return uart_read ( uart, UART_RBR );
+}
+
+extern void uart_transmit ( struct uart *uart, uint8_t data );
+extern void uart_flush ( struct uart *uart );
+extern int uart_init ( struct uart *uart, unsigned int baud, uint8_t lcr );
+
+#endif /* _IPXE_UART_H */