Added bit-bashing i2c interface code

src/drivers/bitbash/i2c_bit.c

@@ -0,0 +1,313 @@
+/*
+ * Copyright (C) 2006 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., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <stddef.h>
+#include <stdint.h>
+#include <errno.h>
+#include <assert.h>
+#include <gpxe/bitbash.h>
+#include <gpxe/i2c.h>
+
+/** @file
+ *
+ * I2C bit-bashing interface
+ *
+ * This implements a simple I2C master via a bit-bashing interface
+ * that provides two lines: SCL (clock) and SDA (data).
+ */
+
+/**
+ * Set state of I2C SCL line
+ *
+ * @v basher		Bit-bashing interface
+ * @v state		New state of SCL
+ */
+static inline __attribute__ (( always_inline )) void
+setscl ( struct bit_basher *basher, int state ) {
+	write_bit ( basher, I2C_BIT_SCL, state );
+}
+
+/**
+ * Set state of I2C SDA line
+ *
+ * @v basher		Bit-bashing interface
+ * @v state		New state of SDA
+ */
+static inline __attribute__ (( always_inline )) void
+setsda ( struct bit_basher *basher, int state ) {
+	write_bit ( basher, I2C_BIT_SDA, state );
+}
+
+/**
+ * Get state of I2C SDA line
+ *
+ * @v basher		Bit-bashing interface
+ * @ret state		State of SDA
+ */
+static inline __attribute__ (( always_inline )) int
+getsda ( struct bit_basher *basher ) {
+	return read_bit ( basher, I2C_BIT_SDA );
+}
+
+/**
+ * Send an I2C start condition
+ *
+ * @v basher		Bit-bashing interface
+ */
+static void i2c_start ( struct bit_basher *basher ) {
+	setscl ( basher, 1 );
+	setsda ( basher, 0 );
+	setscl ( basher, 0 );
+	setsda ( basher, 1 );
+}
+
+/**
+ * Send an I2C data bit
+ *
+ * @v basher		Bit-bashing interface
+ * @v bit		Bit to send
+ */
+static void i2c_send_bit ( struct bit_basher *basher, int bit ) {
+	setsda ( basher, bit );
+	setscl ( basher, 1 );
+	setscl ( basher, 0 );
+	setsda ( basher, 1 );
+}
+
+/**
+ * Receive an I2C data bit
+ *
+ * @v basher		Bit-bashing interface
+ * @ret bit		Received bit
+ */
+static int i2c_recv_bit ( struct bit_basher *basher ) {
+	int bit;
+
+	setscl ( basher, 1 );
+	bit = getsda ( basher );
+	setscl ( basher, 0 );
+	return bit;
+}
+
+/**
+ * Send an I2C stop condition
+ *
+ * @v basher		Bit-bashing interface
+ */
+static void i2c_stop ( struct bit_basher *basher ) {
+	setsda ( basher, 0 );
+	setscl ( basher, 1 );
+	setsda ( basher, 1 );
+}
+
+/**
+ * Send byte via I2C bus and check for acknowledgement
+ *
+ * @v basher		Bit-bashing interface
+ * @v byte		Byte to send
+ * @ret rc		Return status code
+ *
+ * Sends a byte via the I2C bus and checks for an acknowledgement from
+ * the slave device.
+ */
+static int i2c_send_byte ( struct bit_basher *basher, uint8_t byte ) {
+	int i;
+	
+	/* Send byte */
+	for ( i = 8 ; i ; i-- ) {
+		i2c_send_bit ( basher, byte & 0x80 );
+		byte <<= 1;
+	}
+
+	/* Check for acknowledgement from slave */
+	return ( i2c_recv_bit ( basher ) == 0 ? 0 : -EIO );
+}
+
+/**
+ * Receive byte via I2C bus
+ *
+ * @v basher		Bit-bashing interface
+ * @ret byte		Received byte
+ *
+ * Receives a byte via the I2C bus and sends NACK to the slave device.
+ */
+static uint8_t i2c_recv_byte ( struct bit_basher *basher ) {
+	uint8_t value = 0;
+	int i;
+
+	/* Receive byte */
+	for ( i = 8 ; i ; i-- ) {
+		value <<= 1;
+		value |= i2c_recv_bit ( basher );
+	}
+
+	/* Send NACK */
+	i2c_send_bit ( basher, 1 );
+
+	return value;
+}
+
+/**
+ * Select I2C device for reading or writing
+ *
+ * @v basher		Bit-bashing interface
+ * @v i2cdev		I2C device
+ * @v direction		I2C_READ or I2C_WRITE
+ * @ret rc		Return status code
+ */
+static int i2c_select ( struct bit_basher *basher, struct i2c_device *i2cdev,
+			unsigned int direction ) {
+	unsigned int address;
+	int rc;
+
+	i2c_start ( basher );
+
+	/* First byte of the address */
+	address = i2cdev->address;
+	if ( i2cdev->tenbit ) {
+		address |= I2C_TENBIT_ADDRESS;
+		address >>= 8;
+	}
+	if ( ( rc = i2c_send_byte ( basher, 
+				    ( ( address << 1 ) | direction ) ) ) != 0 )
+		return rc;
+
+	/* Second byte of the address (10-bit addresses only) */
+	if ( i2cdev->tenbit ) {
+		if ( ( rc = i2c_send_byte ( basher,
+					    ( i2cdev->address & 0xff ) ) ) !=0)
+			return rc;
+	}
+
+	return 0;
+}
+
+/**
+ * Read data from I2C device via bit-bashing interface
+ *
+ * @v i2c		I2C interface
+ * @v i2cdev		I2C device
+ * @v offset		Starting offset within the device
+ * @v data		Data buffer
+ * @v len		Length of data buffer
+ * @ret rc		Return status code
+ *
+ * Note that attempting to read zero bytes of data is a valid way to
+ * check for I2C device presence.
+ */
+static int i2c_bit_read ( struct i2c_interface *i2c,
+			  struct i2c_device *i2cdev, unsigned int offset,
+			  uint8_t *data, unsigned int len ) {
+	struct i2c_bit_basher *i2cbit
+		= container_of ( i2c, struct i2c_bit_basher, i2c );
+	struct bit_basher *basher = &i2cbit->basher;
+	int rc = 0;
+
+	DBG ( "Reading from I2C device %x: ", i2cdev->address );
+
+	while ( 1 ) {
+
+		/* Select device for writing */
+		if ( ( rc = i2c_select ( basher, i2cdev, I2C_WRITE ) ) != 0 )
+			break;
+
+		/* Abort at end of data */
+		if ( ! ( len-- ) )
+			break;
+
+		/* Select offset */
+		if ( ( rc = i2c_send_byte ( basher, offset++ ) ) != 0 )
+			break;
+		
+		/* Select device for reading */
+		if ( ( rc = i2c_select ( basher, i2cdev, I2C_READ ) ) != 0 )
+			break;
+
+		/* Read byte */
+		*data++ = i2c_recv_byte ( basher );
+		DBG ( "%02x ", *(data - 1) );
+	}
+	
+	DBG ( "%s\n", ( rc ? "failed" : "" ) );
+	i2c_stop ( basher );
+	return rc;
+}
+
+/**
+ * Write data to I2C device via bit-bashing interface
+ *
+ * @v i2c		I2C interface
+ * @v i2cdev		I2C device
+ * @v offset		Starting offset within the device
+ * @v data		Data buffer
+ * @v len		Length of data buffer
+ * @ret rc		Return status code
+ *
+ * Note that attempting to write zero bytes of data is a valid way to
+ * check for I2C device presence.
+ */
+static int i2c_bit_write ( struct i2c_interface *i2c,
+			   struct i2c_device *i2cdev, unsigned int offset,
+			   const uint8_t *data, unsigned int len ) {
+	struct i2c_bit_basher *i2cbit
+		= container_of ( i2c, struct i2c_bit_basher, i2c );
+	struct bit_basher *basher = &i2cbit->basher;
+	int rc = 0;
+
+	DBG ( "Writing to I2C device %x: ", i2cdev->address );
+
+	while ( 1 ) {
+
+		/* Select device for writing */
+		if ( ( rc = i2c_select ( basher, i2cdev, I2C_WRITE ) ) != 0 )
+			break;
+		
+		/* Abort at end of data */
+		if ( ! ( len-- ) )
+			break;
+
+		/* Select offset */
+		if ( ( rc = i2c_send_byte ( basher, offset++ ) ) != 0 )
+			break;
+		
+		/* Write data to device */
+		DBG ( "%02x ", *data );
+		if ( ( rc = i2c_send_byte ( basher, *data++ ) ) != 0 )
+			break;
+	}
+	
+	DBG ( "%s\n", ( rc ? "failed" : "" ) );
+	i2c_stop ( basher );
+	return rc;
+}
+
+/**
+ * Initialise I2C bit-bashing interface
+ *
+ * @v i2cbit		I2C bit-bashing interface
+ */
+void init_i2c_bit_basher ( struct i2c_bit_basher *i2cbit ) {
+	struct bit_basher *basher = &i2cbit->basher;
+	
+	assert ( basher->read != NULL );
+	assert ( basher->write != NULL );
+	i2cbit->i2c.read = i2c_bit_read;
+	i2cbit->i2c.write = i2c_bit_write;
+	basher->udelay = I2C_UDELAY;
+	i2c_stop ( basher );
+}

src/include/gpxe/i2c.h

@@ -0,0 +1,109 @@
+#ifndef _GPXE_I2C_H
+#define _GPXE_I2C_H
+
+/** @file
+ *
+ * I2C interface
+ *
+ */
+
+#include <stdint.h>
+
+/** An I2C device
+ *
+ * An I2C device represents a specific slave device on an I2C bus.  It
+ * is accessed via an I2C interface.
+ */
+struct i2c_device {
+	/** Address of this device */
+	unsigned int address;
+	/** Flag indicating a ten-bit address format */
+	int tenbit;
+};
+
+/** An I2C interface
+ *
+ * An I2C interface provides access to an I2C bus, via which I2C
+ * devices may be reached.
+ */
+struct i2c_interface {
+	/**
+	 * Read data from I2C device
+	 *
+	 * @v i2c		I2C interface
+	 * @v i2cdev		I2C device
+	 * @v offset		Starting offset within the device
+	 * @v data		Data buffer
+	 * @v len		Length of data buffer
+	 * @ret rc		Return status code
+	 */
+	int ( * read ) ( struct i2c_interface *i2c, struct i2c_device *i2cdev,
+			 unsigned int offset, uint8_t *data,
+			 unsigned int len );
+	/**
+	 * Write data to I2C device
+	 *
+	 * @v i2c		I2C interface
+	 * @v i2cdev		I2C device
+	 * @v offset		Starting offset within the device
+	 * @v data		Data buffer
+	 * @v len		Length of data buffer
+	 * @ret rc		Return status code
+	 */
+	int ( * write ) ( struct i2c_interface *i2c, struct i2c_device *i2cdev,
+			  unsigned int offset, const uint8_t *data,
+			  unsigned int len );
+};
+
+/** A bit-bashing I2C interface
+ *
+ * This provides a standardised way to construct I2C buses via a
+ * bit-bashing interface.
+ */
+struct i2c_bit_basher {
+	/** I2C interface */
+	struct i2c_interface i2c;
+	/** Bit-bashing interface */
+	struct bit_basher basher;
+};
+
+/** Ten-bit address marker
+ *
+ * This value is ORed with the I2C device address to indicate a
+ * ten-bit address format on the bus.
+ */
+#define I2C_TENBIT_ADDRESS 0x7800
+
+/** An I2C write command */
+#define I2C_WRITE 0
+
+/** An I2C read command */
+#define I2C_READ 1
+
+/** Bit indices used for I2C bit-bashing interface */
+enum {
+	I2C_BIT_SCL = 0,
+	I2C_BIT_SDA,
+};
+
+/** Delay required for bit-bashing operation */
+#define I2C_UDELAY 5
+
+/**
+ * Check presence of I2C device
+ *
+ * @v i2c		I2C interface
+ * @v i2cdev		I2C device
+ * @ret rc		Return status code
+ *
+ * Checks for the presence of the device on the I2C bus by attempting
+ * a zero-length write.
+ */
+static inline int i2c_check_presence ( struct i2c_interface *i2c,
+				       struct i2c_device *i2cdev ) {
+	return i2c->write ( i2c, i2cdev, 0, NULL, 0 );
+}
+
+extern void init_i2c_bit_basher ( struct i2c_bit_basher *i2cbit );
+
+#endif /* _GPXE_I2C_H */