Added bit-bashing i2c interface code
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Michael Brown
parent
476d02051f
commit
3ed40686c9
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/*
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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., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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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 <assert.h>
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#include <gpxe/bitbash.h>
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#include <gpxe/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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* 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 inline __attribute__ (( always_inline )) void
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setscl ( struct bit_basher *basher, int state ) {
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write_bit ( basher, I2C_BIT_SCL, state );
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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 inline __attribute__ (( always_inline )) void
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setsda ( struct bit_basher *basher, int state ) {
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write_bit ( basher, I2C_BIT_SDA, state );
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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 inline __attribute__ (( always_inline )) int
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getsda ( struct bit_basher *basher ) {
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return read_bit ( basher, I2C_BIT_SDA );
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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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/* Send 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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return ( i2c_recv_bit ( basher ) == 0 ? 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 value = 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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value <<= 1;
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value |= i2c_recv_bit ( basher );
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}
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/* Send NACK */
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i2c_send_bit ( basher, 1 );
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return value;
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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 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 direction ) {
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unsigned int address;
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int rc;
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i2c_start ( basher );
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/* First byte of the address */
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address = i2cdev->address;
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if ( i2cdev->tenbit ) {
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address |= I2C_TENBIT_ADDRESS;
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address >>= 8;
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}
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if ( ( rc = i2c_send_byte ( basher,
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( ( address << 1 ) | direction ) ) ) != 0 )
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return rc;
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/* Second byte of the address (10-bit addresses only) */
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if ( i2cdev->tenbit ) {
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if ( ( rc = i2c_send_byte ( basher,
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( i2cdev->address & 0xff ) ) ) !=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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* 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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DBG ( "Reading from I2C device %x: ", i2cdev->address );
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while ( 1 ) {
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/* Select device for writing */
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if ( ( rc = i2c_select ( basher, i2cdev, 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, 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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DBG ( "%02x ", *(data - 1) );
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}
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DBG ( "%s\n", ( rc ? "failed" : "" ) );
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i2c_stop ( 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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DBG ( "Writing to I2C device %x: ", i2cdev->address );
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while ( 1 ) {
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/* Select device for writing */
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if ( ( rc = i2c_select ( basher, i2cdev, 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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DBG ( "%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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DBG ( "%s\n", ( rc ? "failed" : "" ) );
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i2c_stop ( 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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*/
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void init_i2c_bit_basher ( struct i2c_bit_basher *i2cbit ) {
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struct bit_basher *basher = &i2cbit->basher;
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assert ( basher->read != NULL );
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assert ( basher->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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basher->udelay = I2C_UDELAY;
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i2c_stop ( basher );
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}
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#ifndef _GPXE_I2C_H
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#define _GPXE_I2C_H
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/** @file
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*
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* I2C interface
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*
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*/
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#include <stdint.h>
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/** An I2C device
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*
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* An I2C device represents a specific slave device on an I2C bus. It
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* is accessed via an I2C interface.
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*/
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struct i2c_device {
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/** Address of this device */
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unsigned int address;
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/** Flag indicating a ten-bit address format */
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int tenbit;
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};
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/** An I2C interface
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*
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* An I2C interface provides access to an I2C bus, via which I2C
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* devices may be reached.
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*/
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struct i2c_interface {
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/**
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* Read data from I2C device
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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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int ( * read ) ( struct i2c_interface *i2c, struct i2c_device *i2cdev,
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unsigned int offset, uint8_t *data,
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unsigned int len );
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/**
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* Write data to I2C device
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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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int ( * write ) ( struct i2c_interface *i2c, struct i2c_device *i2cdev,
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unsigned int offset, const uint8_t *data,
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unsigned int len );
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};
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/** A bit-bashing I2C interface
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*
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* This provides a standardised way to construct I2C buses via a
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* bit-bashing interface.
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*/
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struct i2c_bit_basher {
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/** I2C interface */
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struct i2c_interface i2c;
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/** Bit-bashing interface */
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struct bit_basher basher;
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};
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/** Ten-bit address marker
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*
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* This value is ORed with the I2C device address to indicate a
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* ten-bit address format on the bus.
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*/
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#define I2C_TENBIT_ADDRESS 0x7800
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/** An I2C write command */
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#define I2C_WRITE 0
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/** An I2C read command */
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#define I2C_READ 1
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/** Bit indices used for I2C bit-bashing interface */
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enum {
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I2C_BIT_SCL = 0,
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I2C_BIT_SDA,
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};
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/** Delay required for bit-bashing operation */
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#define I2C_UDELAY 5
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/**
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* Check presence of I2C device
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*
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* @v i2c I2C interface
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* @v i2cdev I2C device
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* @ret rc Return status code
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*
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* Checks for the presence of the device on the I2C bus by attempting
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* a zero-length write.
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*/
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static inline int i2c_check_presence ( struct i2c_interface *i2c,
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struct i2c_device *i2cdev ) {
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return i2c->write ( i2c, i2cdev, 0, NULL, 0 );
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}
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extern void init_i2c_bit_basher ( struct i2c_bit_basher *i2cbit );
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#endif /* _GPXE_I2C_H */
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