--- /dev/null
+/*
+ * 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., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#include <stddef.h>
+#include <stdint.h>
+#include <errno.h>
+#include <string.h>
+#include <assert.h>
+#include <unistd.h>
+#include <ipxe/bitbash.h>
+#include <ipxe/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).
+ */
+
+/**
+ * Delay between output state changes
+ *
+ * Max rated i2c speed (for the basic i2c protocol) is 100kbps,
+ * i.e. 200k clock transitions per second.
+ */
+static void i2c_delay ( void ) {
+ udelay ( I2C_UDELAY );
+}
+
+/**
+ * Set state of I2C SCL line
+ *
+ * @v basher Bit-bashing interface
+ * @v state New state of SCL
+ */
+static void setscl ( struct bit_basher *basher, int state ) {
+ DBG2 ( "%c", ( state ? '/' : '\\' ) );
+ write_bit ( basher, I2C_BIT_SCL, state );
+ i2c_delay();
+}
+
+/**
+ * Set state of I2C SDA line
+ *
+ * @v basher Bit-bashing interface
+ * @v state New state of SDA
+ */
+static void setsda ( struct bit_basher *basher, int state ) {
+ DBG2 ( "%c", ( state ? '1' : '0' ) );
+ write_bit ( basher, I2C_BIT_SDA, state );
+ i2c_delay();
+}
+
+/**
+ * Get state of I2C SDA line
+ *
+ * @v basher Bit-bashing interface
+ * @ret state State of SDA
+ */
+static int getsda ( struct bit_basher *basher ) {
+ int state;
+ state = read_bit ( basher, I2C_BIT_SDA );
+ DBG2 ( "%c", ( state ? '+' : '-' ) );
+ return state;
+}
+
+/**
+ * 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;
+ int ack;
+
+ /* Send byte */
+ DBG2 ( "[send %02x]", byte );
+ for ( i = 8 ; i ; i-- ) {
+ i2c_send_bit ( basher, byte & 0x80 );
+ byte <<= 1;
+ }
+
+ /* Check for acknowledgement from slave */
+ ack = ( i2c_recv_bit ( basher ) == 0 );
+ DBG2 ( "%s", ( ack ? "[acked]" : "[not acked]" ) );
+
+ return ( ack ? 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 byte = 0;
+ int i;
+
+ /* Receive byte */
+ for ( i = 8 ; i ; i-- ) {
+ byte <<= 1;
+ byte |= ( i2c_recv_bit ( basher ) & 0x1 );
+ }
+
+ /* Send NACK */
+ i2c_send_bit ( basher, 1 );
+
+ DBG2 ( "[rcvd %02x]", byte );
+ return byte;
+}
+
+/**
+ * Select I2C device for reading or writing
+ *
+ * @v basher Bit-bashing interface
+ * @v i2cdev I2C device
+ * @v offset Starting offset within the 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 offset, unsigned int direction ) {
+ unsigned int address;
+ int shift;
+ unsigned int byte;
+ int rc;
+
+ i2c_start ( basher );
+
+ /* Calculate address to appear on bus */
+ address = ( ( ( i2cdev->dev_addr |
+ ( offset >> ( 8 * i2cdev->word_addr_len ) ) ) << 1 )
+ | direction );
+
+ /* Send address a byte at a time */
+ for ( shift = ( 8 * ( i2cdev->dev_addr_len - 1 ) ) ;
+ shift >= 0 ; shift -= 8 ) {
+ byte = ( ( address >> shift ) & 0xff );
+ if ( ( rc = i2c_send_byte ( basher, byte ) ) != 0 )
+ return rc;
+ }
+
+ return 0;
+}
+
+/**
+ * Reset I2C bus
+ *
+ * @v basher Bit-bashing interface
+ * @ret rc Return status code
+ *
+ * i2c devices often don't have a reset line, so even a reboot or
+ * system power cycle is sometimes not enough to bring them back to a
+ * known state.
+ */
+static int i2c_reset ( struct bit_basher *basher ) {
+ unsigned int i;
+ int sda;
+
+ /* Clock through several cycles, waiting for an opportunity to
+ * pull SDA low while SCL is high (which creates a start
+ * condition).
+ */
+ open_bit ( basher );
+ setscl ( basher, 0 );
+ setsda ( basher, 1 );
+ for ( i = 0 ; i < I2C_RESET_MAX_CYCLES ; i++ ) {
+ setscl ( basher, 1 );
+ sda = getsda ( basher );
+ if ( sda ) {
+ /* Now that the device will see a start, issue it */
+ i2c_start ( basher );
+ /* Stop the bus to leave it in a known good state */
+ i2c_stop ( basher );
+ DBGC ( basher, "I2CBIT %p reset after %d attempts\n",
+ basher, ( i + 1 ) );
+ close_bit ( basher );
+ return 0;
+ }
+ setscl ( basher, 0 );
+ }
+
+ DBGC ( basher, "I2CBIT %p could not reset after %d attempts\n",
+ basher, i );
+ close_bit ( basher );
+ return -ETIMEDOUT;
+}
+
+/**
+ * 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;
+
+ DBGC ( basher, "I2CBIT %p reading from device %x: ",
+ basher, i2cdev->dev_addr );
+
+ open_bit ( basher );
+
+ for ( ; ; data++, offset++ ) {
+
+ /* Select device for writing */
+ if ( ( rc = i2c_select ( basher, i2cdev, offset,
+ 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, offset,
+ I2C_READ ) ) != 0 )
+ break;
+
+ /* Read byte */
+ *data = i2c_recv_byte ( basher );
+ DBGC ( basher, "%02x ", *data );
+ }
+
+ DBGC ( basher, "%s\n", ( rc ? "failed" : "" ) );
+ i2c_stop ( basher );
+ close_bit ( 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;
+
+ DBGC ( basher, "I2CBIT %p writing to device %x: ",
+ basher, i2cdev->dev_addr );
+
+ open_bit ( basher );
+
+ for ( ; ; data++, offset++ ) {
+
+ /* Select device for writing */
+ if ( ( rc = i2c_select ( basher, i2cdev, offset,
+ 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 */
+ DBGC ( basher, "%02x ", *data );
+ if ( ( rc = i2c_send_byte ( basher, *data ) ) != 0 )
+ break;
+ }
+
+ DBGC ( basher, "%s\n", ( rc ? "failed" : "" ) );
+ i2c_stop ( basher );
+ close_bit ( basher );
+ return rc;
+}
+
+/**
+ * Initialise I2C bit-bashing interface
+ *
+ * @v i2cbit I2C bit-bashing interface
+ * @v bash_op Bit-basher operations
+ */
+int init_i2c_bit_basher ( struct i2c_bit_basher *i2cbit,
+ struct bit_basher_operations *bash_op ) {
+ struct bit_basher *basher = &i2cbit->basher;
+ int rc;
+
+ /* Initialise data structures */
+ basher->op = bash_op;
+ assert ( basher->op->read != NULL );
+ assert ( basher->op->write != NULL );
+ i2cbit->i2c.read = i2c_bit_read;
+ i2cbit->i2c.write = i2c_bit_write;
+
+ /* Reset I2C bus */
+ if ( ( rc = i2c_reset ( basher ) ) != 0 ) {
+ DBGC ( basher, "I2CBIT %p could not reset I2C bus: %s\n",
+ basher, strerror ( rc ) );
+ return rc;
+ }
+
+ return 0;
+}
Code Review / kvmfornfv.git / blobdiff