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linux/drivers/i2c/algos/i2c-algo-bit.c

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/* ------------------------------------------------------------------------- */
/* 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 ----------------------------------------------- */
#define DEB(x) if (i2c_debug>=1) x;
#define DEB2(x) if (i2c_debug>=2) x;
#define DEBSTAT(x) if (i2c_debug>=3) x; /* print several statistical values*/
#define DEBPROTO(x) if (i2c_debug>=9) { x; }
/* debug the protocol by showing transferred bits */
/* ----- global variables --------------------------------------------- */
/* module parameters:
*/
static int i2c_debug;
static int bit_test; /* see if the line-setting functions work */
/* --- 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);
}
static inline void sdahi(struct i2c_algo_bit_data *adap)
{
setsda(adap,1);
udelay(adap->udelay);
}
static inline void scllo(struct i2c_algo_bit_data *adap)
{
setscl(adap,0);
udelay(adap->udelay);
}
/*
* 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();
}
DEBSTAT(printk(KERN_DEBUG "needed %ld jiffies\n", jiffies-start));
done:
udelay(adap->udelay);
return 0;
}
/* --- other auxiliary functions -------------------------------------- */
static void i2c_start(struct i2c_algo_bit_data *adap)
{
/* assert: scl, sda are high */
DEBPROTO(printk("S "));
sdalo(adap);
scllo(adap);
}
static void i2c_repstart(struct i2c_algo_bit_data *adap)
{
/* scl, sda may not be high */
DEBPROTO(printk(" Sr "));
setsda(adap,1);
sclhi(adap);
sdalo(adap);
scllo(adap);
}
static void i2c_stop(struct i2c_algo_bit_data *adap)
{
DEBPROTO(printk("P\n"));
/* assert: scl is low */
sdalo(adap);
sclhi(adap);
sdahi(adap);
}
/* 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, 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 & ( 1 << i );
setsda(adap,sb);
udelay(adap->udelay);
DEBPROTO(printk(KERN_DEBUG "%d",sb!=0));
if (sclhi(adap)<0) { /* timed out */
sdahi(adap); /* we don't want to block the net */
DEB2(printk(KERN_DEBUG " i2c_outb: 0x%02x, timeout at bit #%d\n", c&0xff, i));
return -ETIMEDOUT;
};
/* do arbitration here:
* if ( sb && ! getsda(adap) ) -> ouch! Get out of here.
*/
setscl(adap, 0 );
udelay(adap->udelay);
}
sdahi(adap);
if (sclhi(adap)<0){ /* timeout */
DEB2(printk(KERN_DEBUG " i2c_outb: 0x%02x, timeout at ack\n", c&0xff));
return -ETIMEDOUT;
};
/* read ack: SDA should be pulled down by slave */
ack=getsda(adap); /* ack: sda is pulled low ->success. */
DEB2(printk(KERN_DEBUG " i2c_outb: 0x%02x , getsda() = %d\n", c & 0xff, ack));
DEBPROTO( printk(KERN_DEBUG "[%2.2x]",c&0xff) );
DEBPROTO(if (0==ack){ printk(KERN_DEBUG " A ");} else printk(KERN_DEBUG " NA ") );
scllo(adap);
return 0==ack; /* return 1 if device acked */
/* 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 */
DEB2(printk(KERN_DEBUG " i2c_inb: timeout at bit #%d\n", 7-i));
return -ETIMEDOUT;
};
indata *= 2;
if ( getsda(adap) )
indata |= 0x01;
scllo(adap);
}
/* assert: scl is low */
DEB2(printk(KERN_DEBUG "i2c_inb: 0x%02x\n", indata & 0xff));
DEBPROTO(printk(KERN_DEBUG " 0x%02x", indata & 0xff));
return (int) (indata & 0xff);
}
/*
* 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)
printk(KERN_INFO "i2c-algo-bit.o: Testing SDA only, "
"SCL is not readable.\n");
sda=getsda(adap);
scl=(adap->getscl==NULL?1:getscl(adap));
printk(KERN_DEBUG "i2c-algo-bit.o: (0) scl=%d, sda=%d\n",scl,sda);
if (!scl || !sda ) {
printk(KERN_WARNING "i2c-algo-bit.o: %s seems to be busy.\n", name);
goto bailout;
}
sdalo(adap);
sda=getsda(adap);
scl=(adap->getscl==NULL?1:getscl(adap));
printk(KERN_DEBUG "i2c-algo-bit.o: (1) scl=%d, sda=%d\n",scl,sda);
if ( 0 != sda ) {
printk(KERN_WARNING "i2c-algo-bit.o: SDA stuck high!\n");
goto bailout;
}
if ( 0 == scl ) {
printk(KERN_WARNING "i2c-algo-bit.o: SCL unexpected low "
"while pulling SDA low!\n");
goto bailout;
}
sdahi(adap);
sda=getsda(adap);
scl=(adap->getscl==NULL?1:getscl(adap));
printk(KERN_DEBUG "i2c-algo-bit.o: (2) scl=%d, sda=%d\n",scl,sda);
if ( 0 == sda ) {
printk(KERN_WARNING "i2c-algo-bit.o: SDA stuck low!\n");
goto bailout;
}
if ( 0 == scl ) {
printk(KERN_WARNING "i2c-algo-bit.o: SCL unexpected low "
"while pulling SDA high!\n");
goto bailout;
}
scllo(adap);
sda=getsda(adap);
scl=(adap->getscl==NULL?0:getscl(adap));
printk(KERN_DEBUG "i2c-algo-bit.o: (3) scl=%d, sda=%d\n",scl,sda);
if ( 0 != scl ) {
printk(KERN_WARNING "i2c-algo-bit.o: SCL stuck high!\n");
goto bailout;
}
if ( 0 == sda ) {
printk(KERN_WARNING "i2c-algo-bit.o: SDA unexpected low "
"while pulling SCL low!\n");
goto bailout;
}
sclhi(adap);
sda=getsda(adap);
scl=(adap->getscl==NULL?1:getscl(adap));
printk(KERN_DEBUG "i2c-algo-bit.o: (4) scl=%d, sda=%d\n",scl,sda);
if ( 0 == scl ) {
printk(KERN_WARNING "i2c-algo-bit.o: SCL stuck low!\n");
goto bailout;
}
if ( 0 == sda ) {
printk(KERN_WARNING "i2c-algo-bit.o: SDA unexpected low "
"while pulling SCL high!\n");
goto bailout;
}
printk(KERN_INFO "i2c-algo-bit.o: %s passed test.\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)
break; /* success! */
i2c_stop(adap);
udelay(5/*adap->udelay*/);
if (i==retries) /* no success */
break;
i2c_start(adap);
udelay(adap->udelay);
}
DEB2(if (i)
printk(KERN_DEBUG "i2c-algo-bit.o: Used %d tries to %s client at 0x%02x : %s\n",
i+1, addr & 1 ? "read" : "write", addr>>1,
ret==1 ? "success" : ret==0 ? "no ack" : "failed, timeout?" )
);
return ret;
}
static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
{
struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
char c;
const 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) {
c = *temp;
DEB2(dev_dbg(&i2c_adap->dev, "sendbytes: writing %2.2X\n", c&0xff));
retval = i2c_outb(i2c_adap,c);
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");
i2c_stop(adap);
return (retval<0)? retval : -EFAULT;
/* got a better one ?? */
}
}
return wrcount;
}
static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
{
int inval;
int rdcount=0; /* counts bytes read */
struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
char *temp = msg->buf;
int count = msg->len;
while (count > 0) {
inval = i2c_inb(i2c_adap);
if (inval>=0) {
*temp = inval;
rdcount++;
} else { /* read timed out */
printk(KERN_ERR "i2c-algo-bit.o: readbytes: i2c_inb timed out.\n");
break;
}
temp++;
count--;
if (msg->flags & I2C_M_NO_RD_ACK)
continue;
if ( count > 0 ) { /* send ack */
sdalo(adap);
DEBPROTO(printk(" Am "));
} else {
sdahi(adap); /* neg. ack on last byte */
DEBPROTO(printk(" NAm "));
}
if (sclhi(adap)<0) { /* timeout */
sdahi(adap);
printk(KERN_ERR "i2c-algo-bit.o: readbytes: Timeout at ack\n");
return -ETIMEDOUT;
};
scllo(adap);
sdahi(adap);
}
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);
DEB2(printk(KERN_DEBUG "addr0: %d\n",addr));
/* try extended address code...*/
ret = try_address(i2c_adap, addr, retries);
if ((ret != 1) && !nak_ok) {
printk(KERN_ERR "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 */
printk(KERN_ERR "died at 2nd address code.\n");
return -EREMOTEIO;
}
if ( flags & I2C_M_RD ) {
i2c_repstart(adap);
/* okay, now switch into reading mode */
addr |= 0x01;
ret = try_address(i2c_adap, addr, retries);
if ((ret!=1) && !nak_ok) {
printk(KERN_ERR "died at extended 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;
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) {
i2c_repstart(adap);
}
ret = bit_doAddress(i2c_adap, pmsg);
if ((ret != 0) && !nak_ok) {
DEB2(printk(KERN_DEBUG "i2c-algo-bit.o: NAK from device addr %2.2x msg #%d\n"
,msgs[i].addr,i));
return (ret<0) ? ret : -EREMOTEIO;
}
}
if (pmsg->flags & I2C_M_RD ) {
/* read bytes into buffer*/
ret = readbytes(i2c_adap, pmsg);
DEB2(printk(KERN_DEBUG "i2c-algo-bit.o: read %d bytes.\n",ret));
if (ret < pmsg->len ) {
return (ret<0)? ret : -EREMOTEIO;
}
} else {
/* write bytes from buffer */
ret = sendbytes(i2c_adap, pmsg);
DEB2(printk(KERN_DEBUG "i2c-algo-bit.o: wrote %d bytes.\n",ret));
if (ret < pmsg->len ) {
return (ret<0) ? ret : -EREMOTEIO;
}
}
}
i2c_stop(adap);
return num;
}
static u32 bit_func(struct i2c_adapter *adap)
{
return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
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
*/
int i2c_bit_add_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;
}
DEB2(dev_dbg(&adap->dev, "hw routines registered.\n"));
/* 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 i2c_add_adapter(adap);
}
int i2c_bit_del_bus(struct i2c_adapter *adap)
{
return i2c_del_adapter(adap);
}
EXPORT_SYMBOL(i2c_bit_add_bus);
EXPORT_SYMBOL(i2c_bit_del_bus);
MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm");
MODULE_LICENSE("GPL");
module_param(bit_test, bool, 0);
module_param(i2c_debug, int, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(bit_test, "Test the lines of the bus to see if it is stuck");
MODULE_PARM_DESC(i2c_debug,
"debug level - 0 off; 1 normal; 2,3 more verbose; 9 bit-protocol");
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