408 lines
9.6 KiB
C
408 lines
9.6 KiB
C
/*
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* Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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* 02110-1301, USA.
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*
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* You can also choose to distribute this program under the terms of
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* the Unmodified Binary Distribution Licence (as given in the file
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* COPYING.UBDL), provided that you have satisfied its requirements.
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*/
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FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
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#include <stddef.h>
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#include <stdint.h>
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#include <errno.h>
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#include <string.h>
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#include <assert.h>
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#include <unistd.h>
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#include <ipxe/bitbash.h>
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#include <ipxe/i2c.h>
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/** @file
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*
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* I2C bit-bashing interface
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*
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* This implements a simple I2C master via a bit-bashing interface
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* that provides two lines: SCL (clock) and SDA (data).
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*/
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/**
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* Delay between output state changes
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*
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* Max rated i2c speed (for the basic i2c protocol) is 100kbps,
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* i.e. 200k clock transitions per second.
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*/
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static void i2c_delay ( void ) {
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udelay ( I2C_UDELAY );
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}
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/**
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* Set state of I2C SCL line
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*
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* @v basher Bit-bashing interface
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* @v state New state of SCL
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*/
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static void setscl ( struct bit_basher *basher, int state ) {
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DBG2 ( "%c", ( state ? '/' : '\\' ) );
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write_bit ( basher, I2C_BIT_SCL, state );
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i2c_delay();
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}
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/**
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* Set state of I2C SDA line
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*
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* @v basher Bit-bashing interface
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* @v state New state of SDA
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*/
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static void setsda ( struct bit_basher *basher, int state ) {
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DBG2 ( "%c", ( state ? '1' : '0' ) );
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write_bit ( basher, I2C_BIT_SDA, state );
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i2c_delay();
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}
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/**
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* Get state of I2C SDA line
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*
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* @v basher Bit-bashing interface
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* @ret state State of SDA
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*/
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static int getsda ( struct bit_basher *basher ) {
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int state;
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state = read_bit ( basher, I2C_BIT_SDA );
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DBG2 ( "%c", ( state ? '+' : '-' ) );
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return state;
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}
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/**
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* Send an I2C start condition
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*
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* @v basher Bit-bashing interface
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*/
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static void i2c_start ( struct bit_basher *basher ) {
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setscl ( basher, 1 );
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setsda ( basher, 0 );
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setscl ( basher, 0 );
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setsda ( basher, 1 );
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}
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/**
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* Send an I2C data bit
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*
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* @v basher Bit-bashing interface
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* @v bit Bit to send
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*/
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static void i2c_send_bit ( struct bit_basher *basher, int bit ) {
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setsda ( basher, bit );
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setscl ( basher, 1 );
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setscl ( basher, 0 );
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setsda ( basher, 1 );
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}
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/**
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* Receive an I2C data bit
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*
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* @v basher Bit-bashing interface
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* @ret bit Received bit
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*/
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static int i2c_recv_bit ( struct bit_basher *basher ) {
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int bit;
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setscl ( basher, 1 );
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bit = getsda ( basher );
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setscl ( basher, 0 );
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return bit;
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}
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/**
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* Send an I2C stop condition
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*
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* @v basher Bit-bashing interface
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*/
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static void i2c_stop ( struct bit_basher *basher ) {
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setsda ( basher, 0 );
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setscl ( basher, 1 );
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setsda ( basher, 1 );
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}
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/**
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* Send byte via I2C bus and check for acknowledgement
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*
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* @v basher Bit-bashing interface
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* @v byte Byte to send
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* @ret rc Return status code
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*
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* Sends a byte via the I2C bus and checks for an acknowledgement from
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* the slave device.
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*/
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static int i2c_send_byte ( struct bit_basher *basher, uint8_t byte ) {
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int i;
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int ack;
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/* Send byte */
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DBG2 ( "[send %02x]", byte );
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for ( i = 8 ; i ; i-- ) {
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i2c_send_bit ( basher, byte & 0x80 );
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byte <<= 1;
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}
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/* Check for acknowledgement from slave */
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ack = ( i2c_recv_bit ( basher ) == 0 );
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DBG2 ( "%s", ( ack ? "[acked]" : "[not acked]" ) );
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return ( ack ? 0 : -EIO );
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}
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/**
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* Receive byte via I2C bus
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*
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* @v basher Bit-bashing interface
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* @ret byte Received byte
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*
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* Receives a byte via the I2C bus and sends NACK to the slave device.
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*/
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static uint8_t i2c_recv_byte ( struct bit_basher *basher ) {
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uint8_t byte = 0;
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int i;
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/* Receive byte */
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for ( i = 8 ; i ; i-- ) {
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byte <<= 1;
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byte |= ( i2c_recv_bit ( basher ) & 0x1 );
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}
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/* Send NACK */
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i2c_send_bit ( basher, 1 );
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DBG2 ( "[rcvd %02x]", byte );
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return byte;
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}
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/**
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* Select I2C device for reading or writing
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*
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* @v basher Bit-bashing interface
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* @v i2cdev I2C device
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* @v offset Starting offset within the device
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* @v direction I2C_READ or I2C_WRITE
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* @ret rc Return status code
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*/
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static int i2c_select ( struct bit_basher *basher, struct i2c_device *i2cdev,
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unsigned int offset, unsigned int direction ) {
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unsigned int address;
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int shift;
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unsigned int byte;
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int rc;
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i2c_start ( basher );
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/* Calculate address to appear on bus */
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address = ( ( ( i2cdev->dev_addr |
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( offset >> ( 8 * i2cdev->word_addr_len ) ) ) << 1 )
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| direction );
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/* Send address a byte at a time */
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for ( shift = ( 8 * ( i2cdev->dev_addr_len - 1 ) ) ;
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shift >= 0 ; shift -= 8 ) {
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byte = ( ( address >> shift ) & 0xff );
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if ( ( rc = i2c_send_byte ( basher, byte ) ) != 0 )
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return rc;
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}
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return 0;
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}
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/**
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* Reset I2C bus
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*
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* @v basher Bit-bashing interface
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* @ret rc Return status code
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*
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* i2c devices often don't have a reset line, so even a reboot or
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* system power cycle is sometimes not enough to bring them back to a
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* known state.
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*/
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static int i2c_reset ( struct bit_basher *basher ) {
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unsigned int i;
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int sda;
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/* Clock through several cycles, waiting for an opportunity to
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* pull SDA low while SCL is high (which creates a start
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* condition).
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*/
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open_bit ( basher );
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setscl ( basher, 0 );
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setsda ( basher, 1 );
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for ( i = 0 ; i < I2C_RESET_MAX_CYCLES ; i++ ) {
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setscl ( basher, 1 );
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sda = getsda ( basher );
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if ( sda ) {
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/* Now that the device will see a start, issue it */
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i2c_start ( basher );
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/* Stop the bus to leave it in a known good state */
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i2c_stop ( basher );
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DBGC ( basher, "I2CBIT %p reset after %d attempts\n",
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basher, ( i + 1 ) );
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close_bit ( basher );
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return 0;
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}
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setscl ( basher, 0 );
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}
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DBGC ( basher, "I2CBIT %p could not reset after %d attempts\n",
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basher, i );
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close_bit ( basher );
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return -ETIMEDOUT;
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}
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/**
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* Read data from I2C device via bit-bashing interface
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*
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* @v i2c I2C interface
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* @v i2cdev I2C device
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* @v offset Starting offset within the device
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* @v data Data buffer
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* @v len Length of data buffer
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* @ret rc Return status code
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*
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* Note that attempting to read zero bytes of data is a valid way to
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* check for I2C device presence.
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*/
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static int i2c_bit_read ( struct i2c_interface *i2c,
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struct i2c_device *i2cdev, unsigned int offset,
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uint8_t *data, unsigned int len ) {
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struct i2c_bit_basher *i2cbit
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= container_of ( i2c, struct i2c_bit_basher, i2c );
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struct bit_basher *basher = &i2cbit->basher;
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int rc = 0;
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DBGC ( basher, "I2CBIT %p reading from device %x: ",
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basher, i2cdev->dev_addr );
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open_bit ( basher );
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for ( ; ; data++, offset++ ) {
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/* Select device for writing */
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if ( ( rc = i2c_select ( basher, i2cdev, offset,
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I2C_WRITE ) ) != 0 )
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break;
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/* Abort at end of data */
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if ( ! ( len-- ) )
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break;
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/* Select offset */
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if ( ( rc = i2c_send_byte ( basher, offset ) ) != 0 )
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break;
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/* Select device for reading */
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if ( ( rc = i2c_select ( basher, i2cdev, offset,
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I2C_READ ) ) != 0 )
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break;
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/* Read byte */
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*data = i2c_recv_byte ( basher );
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DBGC ( basher, "%02x ", *data );
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}
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DBGC ( basher, "%s\n", ( rc ? "failed" : "" ) );
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i2c_stop ( basher );
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close_bit ( basher );
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return rc;
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}
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/**
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* Write data to I2C device via bit-bashing interface
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*
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* @v i2c I2C interface
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* @v i2cdev I2C device
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* @v offset Starting offset within the device
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* @v data Data buffer
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* @v len Length of data buffer
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* @ret rc Return status code
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*
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* Note that attempting to write zero bytes of data is a valid way to
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* check for I2C device presence.
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*/
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static int i2c_bit_write ( struct i2c_interface *i2c,
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struct i2c_device *i2cdev, unsigned int offset,
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const uint8_t *data, unsigned int len ) {
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struct i2c_bit_basher *i2cbit
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= container_of ( i2c, struct i2c_bit_basher, i2c );
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struct bit_basher *basher = &i2cbit->basher;
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int rc = 0;
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DBGC ( basher, "I2CBIT %p writing to device %x: ",
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basher, i2cdev->dev_addr );
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open_bit ( basher );
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for ( ; ; data++, offset++ ) {
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/* Select device for writing */
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if ( ( rc = i2c_select ( basher, i2cdev, offset,
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I2C_WRITE ) ) != 0 )
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break;
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/* Abort at end of data */
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if ( ! ( len-- ) )
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break;
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/* Select offset */
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if ( ( rc = i2c_send_byte ( basher, offset ) ) != 0 )
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break;
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/* Write data to device */
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DBGC ( basher, "%02x ", *data );
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if ( ( rc = i2c_send_byte ( basher, *data ) ) != 0 )
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break;
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}
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DBGC ( basher, "%s\n", ( rc ? "failed" : "" ) );
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i2c_stop ( basher );
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close_bit ( basher );
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return rc;
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}
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/**
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* Initialise I2C bit-bashing interface
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*
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* @v i2cbit I2C bit-bashing interface
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* @v bash_op Bit-basher operations
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*/
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int init_i2c_bit_basher ( struct i2c_bit_basher *i2cbit,
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struct bit_basher_operations *bash_op ) {
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struct bit_basher *basher = &i2cbit->basher;
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int rc;
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/* Initialise data structures */
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basher->op = bash_op;
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assert ( basher->op->read != NULL );
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assert ( basher->op->write != NULL );
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i2cbit->i2c.read = i2c_bit_read;
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i2cbit->i2c.write = i2c_bit_write;
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/* Reset I2C bus */
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if ( ( rc = i2c_reset ( basher ) ) != 0 ) {
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DBGC ( basher, "I2CBIT %p could not reset I2C bus: %s\n",
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basher, strerror ( rc ) );
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return rc;
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}
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return 0;
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}
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