1 /* -------------------------------------------------------------------------
2 * i2c-algo-bit.c i2c driver algorithms for bit-shift adapters
3 * -------------------------------------------------------------------------
4 * Copyright (C) 1995-2000 Simon G. Vogl
6 This program is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2 of the License, or
9 (at your option) any later version.
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program; if not, write to the Free Software
18 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
19 * ------------------------------------------------------------------------- */
21 /* With some changes from Frodo Looijaard <frodol@dds.nl>, Kyösti Mälkki
22 <kmalkki@cc.hut.fi> and Jean Delvare <khali@linux-fr.org> */
24 #include <linux/kernel.h>
25 #include <linux/module.h>
26 #include <linux/delay.h>
27 #include <linux/init.h>
28 #include <linux/errno.h>
29 #include <linux/sched.h>
30 #include <linux/i2c.h>
31 #include <linux/i2c-algo-bit.h>
34 /* ----- global defines ----------------------------------------------- */
37 #define bit_dbg(level, dev, format, args...) \
39 if (i2c_debug >= level) \
40 dev_dbg(dev, format, ##args); \
43 #define bit_dbg(level, dev, format, args...) \
47 /* ----- global variables --------------------------------------------- */
49 static int bit_test; /* see if the line-setting functions work */
50 module_param(bit_test, bool, 0);
51 MODULE_PARM_DESC(bit_test, "Test the lines of the bus to see if it is stuck");
54 static int i2c_debug = 1;
55 module_param(i2c_debug, int, S_IRUGO | S_IWUSR);
56 MODULE_PARM_DESC(i2c_debug,
57 "debug level - 0 off; 1 normal; 2 verbose; 3 very verbose");
60 /* --- setting states on the bus with the right timing: --------------- */
62 #define setsda(adap, val) adap->setsda(adap->data, val)
63 #define setscl(adap, val) adap->setscl(adap->data, val)
64 #define getsda(adap) adap->getsda(adap->data)
65 #define getscl(adap) adap->getscl(adap->data)
67 static inline void sdalo(struct i2c_algo_bit_data *adap)
70 udelay((adap->udelay + 1) / 2);
73 static inline void sdahi(struct i2c_algo_bit_data *adap)
76 udelay((adap->udelay + 1) / 2);
79 static inline void scllo(struct i2c_algo_bit_data *adap)
82 udelay(adap->udelay / 2);
86 * Raise scl line, and do checking for delays. This is necessary for slower
89 static int sclhi(struct i2c_algo_bit_data *adap)
95 /* Not all adapters have scl sense line... */
100 while (!getscl(adap)) {
101 /* This hw knows how to read the clock line, so we wait
102 * until it actually gets high. This is safer as some
103 * chips may hold it low ("clock stretching") while they
104 * are processing data internally.
106 if (time_after(jiffies, start + adap->timeout))
111 if (jiffies != start && i2c_debug >= 3)
112 pr_debug("i2c-algo-bit: needed %ld jiffies for SCL to go "
113 "high\n", jiffies - start);
117 udelay(adap->udelay);
122 /* --- other auxiliary functions -------------------------------------- */
123 static void i2c_start(struct i2c_algo_bit_data *adap)
125 /* assert: scl, sda are high */
127 udelay(adap->udelay);
131 static void i2c_repstart(struct i2c_algo_bit_data *adap)
133 /* assert: scl is low */
137 udelay(adap->udelay);
142 static void i2c_stop(struct i2c_algo_bit_data *adap)
144 /* assert: scl is low */
148 udelay(adap->udelay);
153 /* send a byte without start cond., look for arbitration,
154 check ackn. from slave */
156 * 1 if the device acknowledged
157 * 0 if the device did not ack
158 * -ETIMEDOUT if an error occurred (while raising the scl line)
160 static int i2c_outb(struct i2c_adapter *i2c_adap, unsigned char c)
165 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
167 /* assert: scl is low */
168 for (i = 7; i >= 0; i--) {
171 udelay((adap->udelay + 1) / 2);
172 if (sclhi(adap) < 0) { /* timed out */
173 bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
174 "timeout at bit #%d\n", (int)c, i);
177 /* FIXME do arbitration here:
178 * if (sb && !getsda(adap)) -> ouch! Get out of here.
180 * Report a unique code, so higher level code can retry
181 * the whole (combined) message and *NOT* issue STOP.
186 if (sclhi(adap) < 0) { /* timeout */
187 bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
188 "timeout at ack\n", (int)c);
192 /* read ack: SDA should be pulled down by slave, or it may
193 * NAK (usually to report problems with the data we wrote).
195 ack = !getsda(adap); /* ack: sda is pulled low -> success */
196 bit_dbg(2, &i2c_adap->dev, "i2c_outb: 0x%02x %s\n", (int)c,
201 /* assert: scl is low (sda undef) */
205 static int i2c_inb(struct i2c_adapter *i2c_adap)
207 /* read byte via i2c port, without start/stop sequence */
208 /* acknowledge is sent in i2c_read. */
210 unsigned char indata = 0;
211 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
213 /* assert: scl is low */
215 for (i = 0; i < 8; i++) {
216 if (sclhi(adap) < 0) { /* timeout */
217 bit_dbg(1, &i2c_adap->dev, "i2c_inb: timeout at bit "
225 udelay(i == 7 ? adap->udelay / 2 : adap->udelay);
227 /* assert: scl is low */
232 * Sanity check for the adapter hardware - check the reaction of
233 * the bus lines only if it seems to be idle.
235 static int test_bus(struct i2c_adapter *i2c_adap)
237 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
238 const char *name = i2c_adap->name;
241 if (adap->pre_xfer) {
242 ret = adap->pre_xfer(i2c_adap);
247 if (adap->getscl == NULL)
248 pr_info("%s: Testing SDA only, SCL is not readable\n", name);
251 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
253 printk(KERN_WARNING "%s: bus seems to be busy\n", name);
259 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
261 printk(KERN_WARNING "%s: SDA stuck high!\n", name);
265 printk(KERN_WARNING "%s: SCL unexpected low "
266 "while pulling SDA low!\n", name);
272 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
274 printk(KERN_WARNING "%s: SDA stuck low!\n", name);
278 printk(KERN_WARNING "%s: SCL unexpected low "
279 "while pulling SDA high!\n", name);
285 scl = (adap->getscl == NULL) ? 0 : getscl(adap);
287 printk(KERN_WARNING "%s: SCL stuck high!\n", name);
291 printk(KERN_WARNING "%s: SDA unexpected low "
292 "while pulling SCL low!\n", name);
298 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
300 printk(KERN_WARNING "%s: SCL stuck low!\n", name);
304 printk(KERN_WARNING "%s: SDA unexpected low "
305 "while pulling SCL high!\n", name);
310 adap->post_xfer(i2c_adap);
312 pr_info("%s: Test OK\n", name);
319 adap->post_xfer(i2c_adap);
324 /* ----- Utility functions
327 /* try_address tries to contact a chip for a number of
328 * times before it gives up.
331 * 0 chip did not answer
332 * -x transmission error
334 static int try_address(struct i2c_adapter *i2c_adap,
335 unsigned char addr, int retries)
337 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
340 for (i = 0; i <= retries; i++) {
341 ret = i2c_outb(i2c_adap, addr);
342 if (ret == 1 || i == retries)
344 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
346 udelay(adap->udelay);
348 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
352 bit_dbg(1, &i2c_adap->dev, "Used %d tries to %s client at "
353 "0x%02x: %s\n", i + 1,
354 addr & 1 ? "read from" : "write to", addr >> 1,
355 ret == 1 ? "success" : "failed, timeout?");
359 static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
361 const unsigned char *temp = msg->buf;
362 int count = msg->len;
363 unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
368 retval = i2c_outb(i2c_adap, *temp);
370 /* OK/ACK; or ignored NAK */
371 if ((retval > 0) || (nak_ok && (retval == 0))) {
376 /* A slave NAKing the master means the slave didn't like
377 * something about the data it saw. For example, maybe
378 * the SMBus PEC was wrong.
380 } else if (retval == 0) {
381 dev_err(&i2c_adap->dev, "sendbytes: NAK bailout.\n");
384 /* Timeout; or (someday) lost arbitration
386 * FIXME Lost ARB implies retrying the transaction from
387 * the first message, after the "winning" master issues
388 * its STOP. As a rule, upper layer code has no reason
389 * to know or care about this ... it is *NOT* an error.
392 dev_err(&i2c_adap->dev, "sendbytes: error %d\n",
400 static int acknak(struct i2c_adapter *i2c_adap, int is_ack)
402 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
404 /* assert: sda is high */
405 if (is_ack) /* send ack */
407 udelay((adap->udelay + 1) / 2);
408 if (sclhi(adap) < 0) { /* timeout */
409 dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n");
416 static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
419 int rdcount = 0; /* counts bytes read */
420 unsigned char *temp = msg->buf;
421 int count = msg->len;
422 const unsigned flags = msg->flags;
425 inval = i2c_inb(i2c_adap);
429 } else { /* read timed out */
436 /* Some SMBus transactions require that we receive the
437 transaction length as the first read byte. */
438 if (rdcount == 1 && (flags & I2C_M_RECV_LEN)) {
439 if (inval <= 0 || inval > I2C_SMBUS_BLOCK_MAX) {
440 if (!(flags & I2C_M_NO_RD_ACK))
442 dev_err(&i2c_adap->dev, "readbytes: invalid "
443 "block length (%d)\n", inval);
446 /* The original count value accounts for the extra
447 bytes, that is, either 1 for a regular transaction,
448 or 2 for a PEC transaction. */
453 bit_dbg(2, &i2c_adap->dev, "readbytes: 0x%02x %s\n",
455 (flags & I2C_M_NO_RD_ACK)
457 : (count ? "A" : "NA"));
459 if (!(flags & I2C_M_NO_RD_ACK)) {
460 inval = acknak(i2c_adap, count);
468 /* doAddress initiates the transfer by generating the start condition (in
469 * try_address) and transmits the address in the necessary format to handle
470 * reads, writes as well as 10bit-addresses.
472 * 0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set
473 * -x an error occurred (like: -EREMOTEIO if the device did not answer, or
474 * -ETIMEDOUT, for example if the lines are stuck...)
476 static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
478 unsigned short flags = msg->flags;
479 unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
480 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
485 retries = nak_ok ? 0 : i2c_adap->retries;
487 if (flags & I2C_M_TEN) {
488 /* a ten bit address */
489 addr = 0xf0 | ((msg->addr >> 7) & 0x03);
490 bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr);
491 /* try extended address code...*/
492 ret = try_address(i2c_adap, addr, retries);
493 if ((ret != 1) && !nak_ok) {
494 dev_err(&i2c_adap->dev,
495 "died at extended address code\n");
498 /* the remaining 8 bit address */
499 ret = i2c_outb(i2c_adap, msg->addr & 0x7f);
500 if ((ret != 1) && !nak_ok) {
501 /* the chip did not ack / xmission error occurred */
502 dev_err(&i2c_adap->dev, "died at 2nd address code\n");
505 if (flags & I2C_M_RD) {
506 bit_dbg(3, &i2c_adap->dev, "emitting repeated "
507 "start condition\n");
509 /* okay, now switch into reading mode */
511 ret = try_address(i2c_adap, addr, retries);
512 if ((ret != 1) && !nak_ok) {
513 dev_err(&i2c_adap->dev,
514 "died at repeated address code\n");
518 } else { /* normal 7bit address */
519 addr = msg->addr << 1;
520 if (flags & I2C_M_RD)
522 if (flags & I2C_M_REV_DIR_ADDR)
524 ret = try_address(i2c_adap, addr, retries);
525 if ((ret != 1) && !nak_ok)
532 static int bit_xfer(struct i2c_adapter *i2c_adap,
533 struct i2c_msg msgs[], int num)
535 struct i2c_msg *pmsg;
536 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
538 unsigned short nak_ok;
540 if (adap->pre_xfer) {
541 ret = adap->pre_xfer(i2c_adap);
546 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
548 for (i = 0; i < num; i++) {
550 nak_ok = pmsg->flags & I2C_M_IGNORE_NAK;
551 if (!(pmsg->flags & I2C_M_NOSTART)) {
553 bit_dbg(3, &i2c_adap->dev, "emitting "
554 "repeated start condition\n");
557 ret = bit_doAddress(i2c_adap, pmsg);
558 if ((ret != 0) && !nak_ok) {
559 bit_dbg(1, &i2c_adap->dev, "NAK from "
560 "device addr 0x%02x msg #%d\n",
565 if (pmsg->flags & I2C_M_RD) {
566 /* read bytes into buffer*/
567 ret = readbytes(i2c_adap, pmsg);
569 bit_dbg(2, &i2c_adap->dev, "read %d byte%s\n",
570 ret, ret == 1 ? "" : "s");
571 if (ret < pmsg->len) {
577 /* write bytes from buffer */
578 ret = sendbytes(i2c_adap, pmsg);
580 bit_dbg(2, &i2c_adap->dev, "wrote %d byte%s\n",
581 ret, ret == 1 ? "" : "s");
582 if (ret < pmsg->len) {
592 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
596 adap->post_xfer(i2c_adap);
600 static u32 bit_func(struct i2c_adapter *adap)
602 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
603 I2C_FUNC_SMBUS_READ_BLOCK_DATA |
604 I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
605 I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
609 /* -----exported algorithm data: ------------------------------------- */
611 static const struct i2c_algorithm i2c_bit_algo = {
612 .master_xfer = bit_xfer,
613 .functionality = bit_func,
617 * registering functions to load algorithms at runtime
619 static int __i2c_bit_add_bus(struct i2c_adapter *adap,
620 int (*add_adapter)(struct i2c_adapter *))
622 struct i2c_algo_bit_data *bit_adap = adap->algo_data;
626 ret = test_bus(adap);
631 /* register new adapter to i2c module... */
632 adap->algo = &i2c_bit_algo;
635 ret = add_adapter(adap);
639 /* Complain if SCL can't be read */
640 if (bit_adap->getscl == NULL) {
641 dev_warn(&adap->dev, "Not I2C compliant: can't read SCL\n");
642 dev_warn(&adap->dev, "Bus may be unreliable\n");
647 int i2c_bit_add_bus(struct i2c_adapter *adap)
649 return __i2c_bit_add_bus(adap, i2c_add_adapter);
651 EXPORT_SYMBOL(i2c_bit_add_bus);
653 int i2c_bit_add_numbered_bus(struct i2c_adapter *adap)
655 return __i2c_bit_add_bus(adap, i2c_add_numbered_adapter);
657 EXPORT_SYMBOL(i2c_bit_add_numbered_bus);
659 MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
660 MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm");
661 MODULE_LICENSE("GPL");