/* ------------------------------------------------------------------------- */
/* i2c-algo-bit.c i2c driver algorithms for bit-shift adapters */
/* ------------------------------------------------------------------------- */
/* Copyright (C) 1995-2000 Simon G. Vogl
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
(at your option) 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. */
/* ------------------------------------------------------------------------- */
/* With some changes from Frodo Looijaard <frodol@dds.nl>, Kyösti Mälkki
<kmalkki@cc.hut.fi> and Jean Delvare <khali@linux-fr.org> */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/i2c.h>
#include <linux/i2c-algo-bit.h>
/* ----- global defines ----------------------------------------------- */
#ifdef DEBUG
#define bit_dbg(level, dev, format, args...) \
do { \
if (i2c_debug >= level) \
dev_dbg(dev, format, ##args); \
} while (0)
#else
#define bit_dbg(level, dev, format, args...) \
do {} while (0)
#endif /* DEBUG */
/* ----- global variables --------------------------------------------- */
static int bit_test; /* see if the line-setting functions work */
module_param(bit_test, bool, 0);
MODULE_PARM_DESC(bit_test, "Test the lines of the bus to see if it is stuck");
#ifdef DEBUG
static int i2c_debug = 1;
module_param(i2c_debug, int, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(i2c_debug,
"debug level - 0 off; 1 normal; 2 verbose; 3 very verbose");
#endif
/* --- setting states on the bus with the right timing: --------------- */
#define setsda(adap,val) adap->setsda(adap->data, val)
#define setscl(adap,val) adap->setscl(adap->data, val)
#define getsda(adap) adap->getsda(adap->data)
#define getscl(adap) adap->getscl(adap->data)
static inline void sdalo(struct i2c_algo_bit_data *adap)
{
setsda(adap,0);
udelay((adap->udelay + 1) / 2);
}
static inline void sdahi(struct i2c_algo_bit_data *adap)
{
setsda(adap,1);
udelay((adap->udelay + 1) / 2);
}
static inline void scllo(struct i2c_algo_bit_data *adap)
{
setscl(adap,0);
udelay(adap->udelay / 2);
}
/*
* Raise scl line, and do checking for delays. This is necessary for slower
* devices.
*/
static int sclhi(struct i2c_algo_bit_data *adap)
{
unsigned long start;
setscl(adap,1);
/* Not all adapters have scl sense line... */
if (!adap->getscl)
goto done;
start=jiffies;
while (! getscl(adap) ) {
/* the hw knows how to read the clock line,
* so we wait until it actually gets high.
* This is safer as some chips may hold it low
* while they are processing data internally.
*/
if (time_after_eq(jiffies, start+adap->timeout)) {
return -ETIMEDOUT;
}
cond_resched();
}
#ifdef DEBUG
if (jiffies != start && i2c_debug >= 3)
pr_debug("i2c-algo-bit: needed %ld jiffies for SCL to go "
"high\n", jiffies - start);
#endif
done:
udelay(adap->udelay);
return 0;
}
/* --- other auxiliary functions -------------------------------------- */
static void i2c_start(struct i2c_algo_bit_data *adap)
{
/* assert: scl, sda are high */
setsda(adap, 0);
udelay(adap->udelay);
scllo(adap);
}
static void i2c_repstart(struct i2c_algo_bit_data *adap)
{
/* assert: scl is low */
sdahi(adap);
sclhi(adap);
setsda(adap, 0);
udelay(adap->udelay);
scllo(adap);
}
static void i2c_stop(struct i2c_algo_bit_data *adap)
{
/* assert: scl is low */
sdalo(adap);
sclhi(adap);
setsda(adap, 1);
udelay(adap->udelay);
}
/* send a byte without start cond., look for arbitration,
check ackn. from slave */
/* returns:
* 1 if the device acknowledged
* 0 if the device did not ack
* -ETIMEDOUT if an error occurred (while raising the scl line)
*/
static int i2c_outb(struct i2c_adapter *i2c_adap, unsigned char c)
{
int i;
int sb;
int ack;
struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
/* assert: scl is low */
for ( i=7 ; i>=0 ; i-- ) {
sb = (c >> i) & 1;
setsda(adap,sb);
udelay((adap->udelay + 1) / 2);
if (sclhi(adap)<0) { /* timed out */
bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
"timeout at bit #%d\n", (int)c, i);
return -ETIMEDOUT;
};
/* do arbitration here:
* if ( sb && ! getsda(adap) ) -> ouch! Get out of here.
*/
scllo(adap);
}
sdahi(adap);
if (sclhi(adap)<0){ /* timeout */
bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
"timeout at ack\n", (int)c);
return -ETIMEDOUT;
};
/* read ack: SDA should be pulled down by slave */
ack = !getsda(adap); /* ack: sda is pulled low -> success */
bit_dbg(2, &i2c_adap->dev, "i2c_outb: 0x%02x %s\n", (int)c,
ack ? "A" : "NA");
scllo(adap);
return ack;
/* assert: scl is low (sda undef) */
}
static int i2c_inb(struct i2c_adapter *i2c_adap)
{
/* read byte via i2c port, without start/stop sequence */
/* acknowledge is sent in i2c_read. */
int i;
unsigned char indata=0;
struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
/* assert: scl is low */
sdahi(adap);
for (i=0;i<8;i++) {
if (sclhi(adap)<0) { /* timeout */
bit_dbg(1, &i2c_adap->dev, "i2c_inb: timeout at bit "
"#%d\n", 7 - i);
return -ETIMEDOUT;
};
indata *= 2;
if ( getsda(adap) )
indata |= 0x01;
setscl(adap, 0);
udelay(i == 7 ? adap->udelay / 2 : adap->udelay);
}
/* assert: scl is low */
return indata;
}
/*
* Sanity check for the adapter hardware - check the reaction of
* the bus lines only if it seems to be idle.
*/
static int test_bus(struct i2c_algo_bit_data *adap, char* name) {
int scl,sda;
if (adap->getscl==NULL)
pr_info("%s: Testing SDA only, SCL is not readable\n", name);
sda=getsda(adap);
scl=(adap->getscl==NULL?1:getscl(adap));
if (!scl || !sda ) {
printk(KERN_WARNING "%s: bus seems to be busy\n", name);
goto bailout;
}
sdalo(adap);
sda=getsda(adap);
scl=(adap->getscl==NULL?1:getscl(adap));
if ( 0 != sda ) {
printk(KERN_WARNING "%s: SDA stuck high!\n", name);
goto bailout;
}
if ( 0 == scl ) {
printk(KERN_WARNING "%s: SCL unexpected low "
"while pulling SDA low!\n", name);
goto bailout;
}
sdahi(adap);
sda=getsda(adap);
scl=(adap->getscl==NULL?1:getscl(adap));
if ( 0 == sda ) {
printk(KERN_WARNING "%s: SDA stuck low!\n", name);
goto bailout;
}
if ( 0 == scl ) {
printk(KERN_WARNING "%s: SCL unexpected low "
"while pulling SDA high!\n", name);
goto bailout;
}
scllo(adap);
sda=getsda(adap);
scl=(adap->getscl==NULL?0:getscl(adap));
if ( 0 != scl ) {
printk(KERN_WARNING "%s: SCL stuck high!\n", name);
goto bailout;
}
if ( 0 == sda ) {
printk(KERN_WARNING "%s: SDA unexpected low "
"while pulling SCL low!\n", name);
goto bailout;
}
sclhi(adap);
sda=getsda(adap);
scl=(adap->getscl==NULL?1:getscl(adap));
if ( 0 == scl ) {
printk(KERN_WARNING "%s: SCL stuck low!\n", name);
goto bailout;
}
if ( 0 == sda ) {
printk(KERN_WARNING "%s: SDA unexpected low "
"while pulling SCL high!\n", name);
goto bailout;
}
pr_info("%s: Test OK\n", name);
return 0;
bailout:
sdahi(adap);
sclhi(adap);
return -ENODEV;
}
/* ----- Utility functions
*/
/* try_address tries to contact a chip for a number of
* times before it gives up.
* return values:
* 1 chip answered
* 0 chip did not answer
* -x transmission error
*/
static int try_address(struct i2c_adapter *i2c_adap,
unsigned char addr, int retries)
{
struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
int i,ret = -1;
for (i=0;i<=retries;i++) {
ret = i2c_outb(i2c_adap,addr);
if (ret == 1 || i == retries)
break;
bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
i2c_stop(adap);
udelay(adap->udelay);
yield();
bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
i2c_start(adap);
}
if (i && ret)
bit_dbg(1, &i2c_adap->dev, "Used %d tries to %s client at "
"0x%02x: %s\n", i + 1,
addr & 1 ? "read from" : "write to", addr >> 1,
ret == 1 ? "success" : "failed, timeout?");
return ret;
}
static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
{
const unsigned char *temp = msg->buf;
int count = msg->len;
unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
int retval;
int wrcount=0;
while (count > 0) {
retval = i2c_outb(i2c_adap, *temp);
if ((retval>0) || (nak_ok && (retval==0))) { /* ok or ignored NAK */
count--;
temp++;
wrcount++;
} else { /* arbitration or no acknowledge */
dev_err(&i2c_adap->dev, "sendbytes: error - bailout.\n");
return (retval<0)? retval : -EFAULT;
/* got a better one ?? */
}
}
return wrcount;
}
static int acknak(struct i2c_adapter *i2c_adap, int is_ack)
{
struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
/* assert: sda is high */
if (is_ack) /* send ack */
setsda(adap, 0);
udelay((adap->udelay + 1) / 2);
if (sclhi(adap) < 0) { /* timeout */
dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n");
return -ETIMEDOUT;
}
scllo(adap);
return 0;
}
static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
{
int inval;
int rdcount=0; /* counts bytes read */
unsigned char *temp = msg->buf;
int count = msg->len;
const unsigned flags = msg->flags;
while (count > 0) {
inval = i2c_inb(i2c_adap);
if (inval>=0) {
*temp = inval;
rdcount++;
} else { /* read timed out */
break;
}
temp++;
count--;
/* Some SMBus transactions require that we receive the
transaction length as the first read byte. */
if (rdcount == 1 && (flags & I2C_M_RECV_LEN)) {
if (inval <= 0 || inval > I2C_SMBUS_BLOCK_MAX) {
if (!(flags & I2C_M_NO_RD_ACK))
acknak(i2c_adap, 0);
dev_err(&i2c_adap->dev, "readbytes: invalid "
"block length (%d)\n", inval);
return -EREMOTEIO;
}
/* The original count value accounts for the extra
bytes, that is, either 1 for a regular transaction,
or 2 for a PEC transaction. */
count += inval;
msg->len += inval;
}
bit_dbg(2, &i2c_adap->dev, "readbytes: 0x%02x %s\n",
inval,
(flags & I2C_M_NO_RD_ACK)
? "(no ack/nak)"
: (count ? "A" : "NA"));
if (!(flags & I2C_M_NO_RD_ACK)) {
inval = acknak(i2c_adap, count);
if (inval < 0)
return inval;
}
}
return rdcount;
}
/* doAddress initiates the transfer by generating the start condition (in
* try_address) and transmits the address in the necessary format to handle
* reads, writes as well as 10bit-addresses.
* returns:
* 0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set
* -x an error occurred (like: -EREMOTEIO if the device did not answer, or
* -ETIMEDOUT, for example if the lines are stuck...)
*/
static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
{
unsigned short flags = msg->flags;
unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
unsigned char addr;
int ret, retries;
retries = nak_ok ? 0 : i2c_adap->retries;
if ( (flags & I2C_M_TEN) ) {
/* a ten bit address */
addr = 0xf0 | (( msg->addr >> 7) & 0x03);
bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr);
/* try extended address code...*/
ret = try_address(i2c_adap, addr, retries);
if ((ret != 1) && !nak_ok) {
dev_err(&i2c_adap->dev,
"died at extended address code\n");
return -EREMOTEIO;
}
/* the remaining 8 bit address */
ret = i2c_outb(i2c_adap,msg->addr & 0x7f);
if ((ret != 1) && !nak_ok) {
/* the chip did not ack / xmission error occurred */
dev_err(&i2c_adap->dev, "died at 2nd address code\n");
return -EREMOTEIO;
}
if ( flags & I2C_M_RD ) {
bit_dbg(3, &i2c_adap->dev, "emitting repeated "
"start condition\n");
i2c_repstart(adap);
/* okay, now switch into reading mode */
addr |= 0x01;
ret = try_address(i2c_adap, addr, retries);
if ((ret!=1) && !nak_ok) {
dev_err(&i2c_adap->dev,
"died at repeated address code\n");
return -EREMOTEIO;
}
}
} else { /* normal 7bit address */
addr = ( msg->addr << 1 );
if (flags & I2C_M_RD )
addr |= 1;
if (flags & I2C_M_REV_DIR_ADDR )
addr ^= 1;
ret = try_address(i2c_adap, addr, retries);
if ((ret!=1) && !nak_ok)
return -EREMOTEIO;
}
return 0;
}
static int bit_xfer(struct i2c_adapter *i2c_adap,
struct i2c_msg msgs[], int num)
{
struct i2c_msg *pmsg;
struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
int i,ret;
unsigned short nak_ok;
bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
i2c_start(adap);
for (i=0;i<num;i++) {
pmsg = &msgs[i];
nak_ok = pmsg->flags & I2C_M_IGNORE_NAK;
if (!(pmsg->flags & I2C_M_NOSTART)) {
if (i) {
bit_dbg(3, &i2c_adap->dev, "emitting "
"repeated start condition\n");
i2c_repstart(adap);
}
ret = bit_doAddress(i2c_adap, pmsg);
if ((ret != 0) && !nak_ok) {
bit_dbg(1, &i2c_adap->dev, "NAK from "
"device addr 0x%02x msg #%d\n",
msgs[i].addr, i);
goto bailout;
}
}
if (pmsg->flags & I2C_M_RD ) {
/* read bytes into buffer*/
ret = readbytes(i2c_adap, pmsg);
if (ret >= 1)
bit_dbg(2, &i2c_adap->dev, "read %d byte%s\n",
ret, ret == 1 ? "" : "s");
if (ret < pmsg->len) {
if (ret >= 0)
ret = -EREMOTEIO;
goto bailout;
}
} else {
/* write bytes from buffer */
ret = sendbytes(i2c_adap, pmsg);
if (ret >= 1)
bit_dbg(2, &i2c_adap->dev, "wrote %d byte%s\n",
ret, ret == 1 ? "" : "s");
if (ret < pmsg->len) {
if (ret >= 0)
ret = -EREMOTEIO;
goto bailout;
}
}
}
ret = i;
bailout:
bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
i2c_stop(adap);
return ret;
}
static u32 bit_func(struct i2c_adapter *adap)
{
return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
I2C_FUNC_SMBUS_READ_BLOCK_DATA |
I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
}
/* -----exported algorithm data: ------------------------------------- */
static const struct i2c_algorithm i2c_bit_algo = {
.master_xfer = bit_xfer,
.functionality = bit_func,
};
/*
* registering functions to load algorithms at runtime
*/
static int i2c_bit_prepare_bus(struct i2c_adapter *adap)
{
struct i2c_algo_bit_data *bit_adap = adap->algo_data;
if (bit_test) {
int ret = test_bus(bit_adap, adap->name);
if (ret<0)
return -ENODEV;
}
/* register new adapter to i2c module... */
adap->algo = &i2c_bit_algo;
adap->timeout = 100; /* default values, should */
adap->retries = 3; /* be replaced by defines */
return 0;
}
int i2c_bit_add_bus(struct i2c_adapter *adap)
{
int err;
err = i2c_bit_prepare_bus(adap);
if (err)
return err;
return i2c_add_adapter(adap);
}
EXPORT_SYMBOL(i2c_bit_add_bus);
int i2c_bit_add_numbered_bus(struct i2c_adapter *adap)
{
int err;
err = i2c_bit_prepare_bus(adap);
if (err)
return err;
return i2c_add_numbered_adapter(adap);
}
EXPORT_SYMBOL(i2c_bit_add_numbered_bus);
MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm");
MODULE_LICENSE("GPL");
