/*!***************************************************************************
*!
*! FILE NAME : i2c.c
*!
*! DESCRIPTION: implements an interface for IIC/I2C, both directly from other
*! kernel modules (i2c_writereg/readreg) and from userspace using
*! ioctl()'s
*!
*! Nov 30 1998 Torbjorn Eliasson Initial version.
*! Bjorn Wesen Elinux kernel version.
*! Jan 14 2000 Johan Adolfsson Fixed PB shadow register stuff -
*! don't use PB_I2C if DS1302 uses same bits,
*! use PB.
*| June 23 2003 Pieter Grimmerink Added 'i2c_sendnack'. i2c_readreg now
*| generates nack on last received byte,
*| instead of ack.
*| i2c_getack changed data level while clock
*| was high, causing DS75 to see a stop condition
*!
*! ---------------------------------------------------------------------------
*!
*! (C) Copyright 1999-2007 Axis Communications AB, LUND, SWEDEN
*!
*!***************************************************************************/
/****************** INCLUDE FILES SECTION ***********************************/
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/string.h>
#include <linux/init.h>
#include <asm/etraxi2c.h>
#include <asm/system.h>
#include <asm/io.h>
#include <asm/delay.h>
#include "i2c.h"
/****************** I2C DEFINITION SECTION *************************/
#define D(x)
#define I2C_MAJOR 123 /* LOCAL/EXPERIMENTAL */
static const char i2c_name[] = "i2c";
#define CLOCK_LOW_TIME 8
#define CLOCK_HIGH_TIME 8
#define START_CONDITION_HOLD_TIME 8
#define STOP_CONDITION_HOLD_TIME 8
#define ENABLE_OUTPUT 0x01
#define ENABLE_INPUT 0x00
#define I2C_CLOCK_HIGH 1
#define I2C_CLOCK_LOW 0
#define I2C_DATA_HIGH 1
#define I2C_DATA_LOW 0
#define i2c_enable()
#define i2c_disable()
/* enable or disable output-enable, to select output or input on the i2c bus */
#define i2c_dir_out() crisv32_io_set_dir(&cris_i2c_data, crisv32_io_dir_out)
#define i2c_dir_in() crisv32_io_set_dir(&cris_i2c_data, crisv32_io_dir_in)
/* control the i2c clock and data signals */
#define i2c_clk(x) crisv32_io_set(&cris_i2c_clk, x)
#define i2c_data(x) crisv32_io_set(&cris_i2c_data, x)
/* read a bit from the i2c interface */
#define i2c_getbit() crisv32_io_rd(&cris_i2c_data)
#define i2c_delay(usecs) udelay(usecs)
static DEFINE_SPINLOCK(i2c_lock); /* Protect directions etc */
/****************** VARIABLE SECTION ************************************/
static struct crisv32_iopin cris_i2c_clk;
static struct crisv32_iopin cris_i2c_data;
/****************** FUNCTION DEFINITION SECTION *************************/
/* generate i2c start condition */
void
i2c_start(void)
{
/*
* SCL=1 SDA=1
*/
i2c_dir_out();
i2c_delay(CLOCK_HIGH_TIME/6);
i2c_data(I2C_DATA_HIGH);
i2c_clk(I2C_CLOCK_HIGH);
i2c_delay(CLOCK_HIGH_TIME);
/*
* SCL=1 SDA=0
*/
i2c_data(I2C_DATA_LOW);
i2c_delay(START_CONDITION_HOLD_TIME);
/*
* SCL=0 SDA=0
*/
i2c_clk(I2C_CLOCK_LOW);
i2c_delay(CLOCK_LOW_TIME);
}
/* generate i2c stop condition */
void
i2c_stop(void)
{
i2c_dir_out();
/*
* SCL=0 SDA=0
*/
i2c_clk(I2C_CLOCK_LOW);
i2c_data(I2C_DATA_LOW);
i2c_delay(CLOCK_LOW_TIME*2);
/*
* SCL=1 SDA=0
*/
i2c_clk(I2C_CLOCK_HIGH);
i2c_delay(CLOCK_HIGH_TIME*2);
/*
* SCL=1 SDA=1
*/
i2c_data(I2C_DATA_HIGH);
i2c_delay(STOP_CONDITION_HOLD_TIME);
i2c_dir_in();
}
/* write a byte to the i2c interface */
void
i2c_outbyte(unsigned char x)
{
int i;
i2c_dir_out();
for (i = 0; i < 8; i++) {
if (x & 0x80) {
i2c_data(I2C_DATA_HIGH);
} else {
i2c_data(I2C_DATA_LOW);
}
i2c_delay(CLOCK_LOW_TIME/2);
i2c_clk(I2C_CLOCK_HIGH);
i2c_delay(CLOCK_HIGH_TIME);
i2c_clk(I2C_CLOCK_LOW);
i2c_delay(CLOCK_LOW_TIME/2);
x <<= 1;
}
i2c_data(I2C_DATA_LOW);
i2c_delay(CLOCK_LOW_TIME/2);
/*
* enable input
*/
i2c_dir_in();
}
/* read a byte from the i2c interface */
unsigned char
i2c_inbyte(void)
{
unsigned char aBitByte = 0;
int i;
/* Switch off I2C to get bit */
i2c_disable();
i2c_dir_in();
i2c_delay(CLOCK_HIGH_TIME/2);
/* Get bit */
aBitByte |= i2c_getbit();
/* Enable I2C */
i2c_enable();
i2c_delay(CLOCK_LOW_TIME/2);
for (i = 1; i < 8; i++) {
aBitByte <<= 1;
/* Clock pulse */
i2c_clk(I2C_CLOCK_HIGH);
i2c_delay(CLOCK_HIGH_TIME);
i2c_clk(I2C_CLOCK_LOW);
i2c_delay(CLOCK_LOW_TIME);
/* Switch off I2C to get bit */
i2c_disable();
i2c_dir_in();
i2c_delay(CLOCK_HIGH_TIME/2);
/* Get bit */
aBitByte |= i2c_getbit();
/* Enable I2C */
i2c_enable();
i2c_delay(CLOCK_LOW_TIME/2);
}
i2c_clk(I2C_CLOCK_HIGH);
i2c_delay(CLOCK_HIGH_TIME);
/*
* we leave the clock low, getbyte is usually followed
* by sendack/nack, they assume the clock to be low
*/
i2c_clk(I2C_CLOCK_LOW);
return aBitByte;
}
/*#---------------------------------------------------------------------------
*#
*# FUNCTION NAME: i2c_getack
*#
*# DESCRIPTION : checks if ack was received from ic2
*#
*#--------------------------------------------------------------------------*/
int
i2c_getack(void)
{
int ack = 1;
/*
* enable output
*/
i2c_dir_out();
/*
* Release data bus by setting
* data high
*/
i2c_data(I2C_DATA_HIGH);
/*
* enable input
*/
i2c_dir_in();
i2c_delay(CLOCK_HIGH_TIME/4);
/*
* generate ACK clock pulse
*/
i2c_clk(I2C_CLOCK_HIGH);
#if 0
/*
* Use PORT PB instead of I2C
* for input. (I2C not working)
*/
i2c_clk(1);
i2c_data(1);
/*
* switch off I2C
*/
i2c_data(1);
i2c_disable();
i2c_dir_in();
#endif
/*
* now wait for ack
*/
i2c_delay(CLOCK_HIGH_TIME/2);
/*
* check for ack
*/
if (i2c_getbit())
ack = 0;
i2c_delay(CLOCK_HIGH_TIME/2);
if (!ack) {
if (!i2c_getbit()) /* receiver pulld SDA low */
ack = 1;
i2c_delay(CLOCK_HIGH_TIME/2);
}
/*
* our clock is high now, make sure data is low
* before we enable our output. If we keep data high
* and enable output, we would generate a stop condition.
*/
#if 0
i2c_data(I2C_DATA_LOW);
/*
* end clock pulse
*/
i2c_enable();
i2c_dir_out();
#endif
i2c_clk(I2C_CLOCK_LOW);
i2c_delay(CLOCK_HIGH_TIME/4);
/*
* enable output
*/
i2c_dir_out();
/*
* remove ACK clock pulse
*/
i2c_data(I2C_DATA_HIGH);
i2c_delay(CLOCK_LOW_TIME/2);
return ack;
}
/*#---------------------------------------------------------------------------
*#
*# FUNCTION NAME: I2C::sendAck
*#
*# DESCRIPTION : Send ACK on received data
*#
*#--------------------------------------------------------------------------*/
void
i2c_sendack(void)
{
/*
* enable output
*/
i2c_delay(CLOCK_LOW_TIME);
i2c_dir_out();
/*
* set ack pulse high
*/
i2c_data(I2C_DATA_LOW);
/*
* generate clock pulse
*/
i2c_delay(CLOCK_HIGH_TIME/6);
i2c_clk(I2C_CLOCK_HIGH);
i2c_delay(CLOCK_HIGH_TIME);
i2c_clk(I2C_CLOCK_LOW);
i2c_delay(CLOCK_LOW_TIME/6);
/*
* reset data out
*/
i2c_data(I2C_DATA_HIGH);
i2c_delay(CLOCK_LOW_TIME);
i2c_dir_in();
}
/*#---------------------------------------------------------------------------
*#
*# FUNCTION NAME: i2c_sendnack
*#
*# DESCRIPTION : Sends NACK on received data
*#
*#--------------------------------------------------------------------------*/
void
i2c_sendnack(void)
{
/*
* enable output
*/
i2c_delay(CLOCK_LOW_TIME);
i2c_dir_out();
/*
* set data high
*/
i2c_data(I2C_DATA_HIGH);
/*
* generate clock pulse
*/
i2c_delay(CLOCK_HIGH_TIME/6);
i2c_clk(I2C_CLOCK_HIGH);
i2c_delay(CLOCK_HIGH_TIME);
i2c_clk(I2C_CLOCK_LOW);
i2c_delay(CLOCK_LOW_TIME);
i2c_dir_in();
}
/*#---------------------------------------------------------------------------
*#
*# FUNCTION NAME: i2c_write
*#
*# DESCRIPTION : Writes a value to an I2C device
*#
*#--------------------------------------------------------------------------*/
int
i2c_write(unsigned char theSlave, void *data, size_t nbytes)
{
int error, cntr = 3;
unsigned char bytes_wrote = 0;
unsigned char value;
unsigned long flags;
spin_lock_irqsave(&i2c_lock, flags);
do {
error = 0;
i2c_start();
/*
* send slave address
*/
i2c_outbyte((theSlave & 0xfe));
/*
* wait for ack
*/
if (!i2c_getack())
error = 1;
/*
* send data
*/
for (bytes_wrote = 0; bytes_wrote < nbytes; bytes_wrote++) {
memcpy(&value, data + bytes_wrote, sizeof value);
i2c_outbyte(value);
/*
* now it's time to wait for ack
*/
if (!i2c_getack())
error |= 4;
}
/*
* end byte stream
*/
i2c_stop();
} while (error && cntr--);
i2c_delay(CLOCK_LOW_TIME);
spin_unlock_irqrestore(&i2c_lock, flags);
return -error;
}
/*#---------------------------------------------------------------------------
*#
*# FUNCTION NAME: i2c_read
*#
*# DESCRIPTION : Reads a value from an I2C device
*#
*#--------------------------------------------------------------------------*/
int
i2c_read(unsigned char theSlave, void *data, size_t nbytes)
{
unsigned char b = 0;
unsigned char bytes_read = 0;
int error, cntr = 3;
unsigned long flags;
spin_lock_irqsave(&i2c_lock, flags);
do {
error = 0;
memset(data, 0, nbytes);
/*
* generate start condition
*/
i2c_start();
/*
* send slave address
*/
i2c_outbyte((theSlave | 0x01));
/*
* wait for ack
*/
if (!i2c_getack())
error = 1;
/*
* fetch data
*/
for (bytes_read = 0; bytes_read < nbytes; bytes_read++) {
b = i2c_inbyte();
memcpy(data + bytes_read, &b, sizeof b);
if (bytes_read < (nbytes - 1))
i2c_sendack();
}
/*
* last received byte needs to be nacked
* instead of acked
*/
i2c_sendnack();
/*
* end sequence
*/
i2c_stop();
} while (error && cntr--);
spin_unlock_irqrestore(&i2c_lock, flags);
return -error;
}
/*#---------------------------------------------------------------------------
*#
*# FUNCTION NAME: i2c_writereg
*#
*# DESCRIPTION : Writes a value to an I2C device
*#
*#--------------------------------------------------------------------------*/
int
i2c_writereg(unsigned char theSlave, unsigned char theReg,
unsigned char theValue)
{
int error, cntr = 3;
unsigned long flags;
spin_lock_irqsave(&i2c_lock, flags);
do {
error = 0;
i2c_start();
/*
* send slave address
*/
i2c_outbyte((theSlave & 0xfe));
/*
* wait for ack
*/
if(!i2c_getack())
error = 1;
/*
* now select register
*/
i2c_dir_out();
i2c_outbyte(theReg);
/*
* now it's time to wait for ack
*/
if(!i2c_getack())
error |= 2;
/*
* send register register data
*/
i2c_outbyte(theValue);
/*
* now it's time to wait for ack
*/
if(!i2c_getack())
error |= 4;
/*
* end byte stream
*/
i2c_stop();
} while(error && cntr--);
i2c_delay(CLOCK_LOW_TIME);
spin_unlock_irqrestore(&i2c_lock, flags);
return -error;
}
/*#---------------------------------------------------------------------------
*#
*# FUNCTION NAME: i2c_readreg
*#
*# DESCRIPTION : Reads a value from the decoder registers.
*#
*#--------------------------------------------------------------------------*/
unsigned char
i2c_readreg(unsigned char theSlave, unsigned char theReg)
{
unsigned char b = 0;
int error, cntr = 3;
unsigned long flags;
spin_lock_irqsave(&i2c_lock, flags);
do {
error = 0;
/*
* generate start condition
*/
i2c_start();
/*
* send slave address
*/
i2c_outbyte((theSlave & 0xfe));
/*
* wait for ack
*/
if(!i2c_getack())
error = 1;
/*
* now select register
*/
i2c_dir_out();
i2c_outbyte(theReg);
/*
* now it's time to wait for ack
*/
if(!i2c_getack())
error |= 2;
/*
* repeat start condition
*/
i2c_delay(CLOCK_LOW_TIME);
i2c_start();
/*
* send slave address
*/
i2c_outbyte(theSlave | 0x01);
/*
* wait for ack
*/
if(!i2c_getack())
error |= 4;
/*
* fetch register
*/
b = i2c_inbyte();
/*
* last received byte needs to be nacked
* instead of acked
*/
i2c_sendnack();
/*
* end sequence
*/
i2c_stop();
} while(error && cntr--);
spin_unlock_irqrestore(&i2c_lock, flags);
return b;
}
static int
i2c_open(struct inode *inode, struct file *filp)
{
return 0;
}
static int
i2c_release(struct inode *inode, struct file *filp)
{
return 0;
}
/* Main device API. ioctl's to write or read to/from i2c registers.
*/
static int
i2c_ioctl(struct inode *inode, struct file *file,
unsigned int cmd, unsigned long arg)
{
if(_IOC_TYPE(cmd) != ETRAXI2C_IOCTYPE) {
return -ENOTTY;
}
switch (_IOC_NR(cmd)) {
case I2C_WRITEREG:
/* write to an i2c slave */
D(printk("i2cw %d %d %d\n",
I2C_ARGSLAVE(arg),
I2C_ARGREG(arg),
I2C_ARGVALUE(arg)));
return i2c_writereg(I2C_ARGSLAVE(arg),
I2C_ARGREG(arg),
I2C_ARGVALUE(arg));
case I2C_READREG:
{
unsigned char val;
/* read from an i2c slave */
D(printk("i2cr %d %d ",
I2C_ARGSLAVE(arg),
I2C_ARGREG(arg)));
val = i2c_readreg(I2C_ARGSLAVE(arg), I2C_ARGREG(arg));
D(printk("= %d\n", val));
return val;
}
default:
return -EINVAL;
}
return 0;
}
static const struct file_operations i2c_fops = {
.owner = THIS_MODULE,
.ioctl = i2c_ioctl,
.open = i2c_open,
.release = i2c_release,
};
static int __init i2c_init(void)
{
static int res;
static int first = 1;
if (!first)
return res;
first = 0;
/* Setup and enable the DATA and CLK pins */
res = crisv32_io_get_name(&cris_i2c_data,
CONFIG_ETRAX_V32_I2C_DATA_PORT);
if (res < 0)
return res;
res = crisv32_io_get_name(&cris_i2c_clk, CONFIG_ETRAX_V32_I2C_CLK_PORT);
crisv32_io_set_dir(&cris_i2c_clk, crisv32_io_dir_out);
return res;
}
static int __init i2c_register(void)
{
int res;
res = i2c_init();
if (res < 0)
return res;
/* register char device */
res = register_chrdev(I2C_MAJOR, i2c_name, &i2c_fops);
if (res < 0) {
printk(KERN_ERR "i2c: couldn't get a major number.\n");
return res;
}
printk(KERN_INFO
"I2C driver v2.2, (c) 1999-2007 Axis Communications AB\n");
return 0;
}
/* this makes sure that i2c_init is called during boot */
module_init(i2c_register);
/****************** END OF FILE i2c.c ********************************/
