linux/drivers/i2c/algos/i2c-algo-bit.c
David Brownell bf3e2d1d9b i2c-algo-bit: Fix NAK/ARB comments
Update comments and logging on return path for byte writes.  NAK is
an error, to be reported or optionally ignored.  Timeouts are always
errors.  Lost arbitration is not currently handled, so don't even list
it as an option in the error message.

Don't return bogus EFAULT code for inappropriate NAK; EIO is better,
there is no bad userspace address in question.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
2008-01-27 18:14:46 +01:00

641 lines
16 KiB
C

/* -------------------------------------------------------------------------
* 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)) {
/* This 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 ("clock stretching") 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;
}
/* FIXME do arbitration here:
* if (sb && !getsda(adap)) -> ouch! Get out of here.
*
* Report a unique code, so higher level code can retry
* the whole (combined) message and *NOT* issue STOP.
*/
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, or it may
* NAK (usually to report problems with the data we wrote).
*/
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 (sda) {
printk(KERN_WARNING "%s: SDA stuck high!\n", name);
goto bailout;
}
if (!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 (!sda) {
printk(KERN_WARNING "%s: SDA stuck low!\n", name);
goto bailout;
}
if (!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 (scl) {
printk(KERN_WARNING "%s: SCL stuck high!\n", name);
goto bailout;
}
if (!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 (!scl) {
printk(KERN_WARNING "%s: SCL stuck low!\n", name);
goto bailout;
}
if (!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);
/* OK/ACK; or ignored NAK */
if ((retval > 0) || (nak_ok && (retval == 0))) {
count--;
temp++;
wrcount++;
/* A slave NAKing the master means the slave didn't like
* something about the data it saw. For example, maybe
* the SMBus PEC was wrong.
*/
} else if (retval == 0) {
dev_err(&i2c_adap->dev, "sendbytes: NAK bailout.\n");
return -EIO;
/* Timeout; or (someday) lost arbitration
*
* FIXME Lost ARB implies retrying the transaction from
* the first message, after the "winning" master issues
* its STOP. As a rule, upper layer code has no reason
* to know or care about this ... it is *NOT* an error.
*/
} else {
dev_err(&i2c_adap->dev, "sendbytes: error %d\n",
retval);
return retval;
}
}
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");