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1/* -------------------------------------------------------------------------
2 * i2c-algo-bit.c i2c driver algorithms for bit-shift adapters
3 * -------------------------------------------------------------------------
4 * Copyright (C) 1995-2000 Simon G. Vogl
5
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.
10
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.
15
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., 51 Franklin Street, Fifth Floor, Boston,
19 MA 02110-1301 USA.
20 * ------------------------------------------------------------------------- */
21
22/* With some changes from Frodo Looijaard <frodol@dds.nl>, Kyösti Mälkki
23 <kmalkki@cc.hut.fi> and Jean Delvare <jdelvare@suse.de> */
24
25#include <linux/kernel.h>
26#include <linux/module.h>
27#include <linux/delay.h>
28#include <linux/errno.h>
29#include <linux/sched.h>
30#include <linux/i2c.h>
31#include <linux/i2c-algo-bit.h>
32
33
34/* ----- global defines ----------------------------------------------- */
35
36#ifdef DEBUG
37#define bit_dbg(level, dev, format, args...) \
38 do { \
39 if (i2c_debug >= level) \
40 dev_dbg(dev, format, ##args); \
41 } while (0)
42#else
43#define bit_dbg(level, dev, format, args...) \
44 do {} while (0)
45#endif /* DEBUG */
46
47/* ----- global variables --------------------------------------------- */
48
49static int bit_test; /* see if the line-setting functions work */
50module_param(bit_test, int, S_IRUGO);
51MODULE_PARM_DESC(bit_test, "lines testing - 0 off; 1 report; 2 fail if stuck");
52
53#ifdef DEBUG
54static int i2c_debug = 1;
55module_param(i2c_debug, int, S_IRUGO | S_IWUSR);
56MODULE_PARM_DESC(i2c_debug,
57 "debug level - 0 off; 1 normal; 2 verbose; 3 very verbose");
58#endif
59
60/* --- setting states on the bus with the right timing: --------------- */
61
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)
66
67static inline void sdalo(struct i2c_algo_bit_data *adap)
68{
69 setsda(adap, 0);
70 udelay((adap->udelay + 1) / 2);
71}
72
73static inline void sdahi(struct i2c_algo_bit_data *adap)
74{
75 setsda(adap, 1);
76 udelay((adap->udelay + 1) / 2);
77}
78
79static inline void scllo(struct i2c_algo_bit_data *adap)
80{
81 setscl(adap, 0);
82 udelay(adap->udelay / 2);
83}
84
85/*
86 * Raise scl line, and do checking for delays. This is necessary for slower
87 * devices.
88 */
89static int sclhi(struct i2c_algo_bit_data *adap)
90{
91 unsigned long start;
92
93 setscl(adap, 1);
94
95 /* Not all adapters have scl sense line... */
96 if (!adap->getscl)
97 goto done;
98
99 start = jiffies;
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.
105 */
106 if (time_after(jiffies, start + adap->timeout)) {
107 /* Test one last time, as we may have been preempted
108 * between last check and timeout test.
109 */
110 if (getscl(adap))
111 break;
112 return -ETIMEDOUT;
113 }
114 cpu_relax();
115 }
116#ifdef DEBUG
117 if (jiffies != start && i2c_debug >= 3)
118 pr_debug("i2c-algo-bit: needed %ld jiffies for SCL to go "
119 "high\n", jiffies - start);
120#endif
121
122done:
123 udelay(adap->udelay);
124 return 0;
125}
126
127
128/* --- other auxiliary functions -------------------------------------- */
129static void i2c_start(struct i2c_algo_bit_data *adap)
130{
131 /* assert: scl, sda are high */
132 setsda(adap, 0);
133 udelay(adap->udelay);
134 scllo(adap);
135}
136
137static void i2c_repstart(struct i2c_algo_bit_data *adap)
138{
139 /* assert: scl is low */
140 sdahi(adap);
141 sclhi(adap);
142 setsda(adap, 0);
143 udelay(adap->udelay);
144 scllo(adap);
145}
146
147
148static void i2c_stop(struct i2c_algo_bit_data *adap)
149{
150 /* assert: scl is low */
151 sdalo(adap);
152 sclhi(adap);
153 setsda(adap, 1);
154 udelay(adap->udelay);
155}
156
157
158
159/* send a byte without start cond., look for arbitration,
160 check ackn. from slave */
161/* returns:
162 * 1 if the device acknowledged
163 * 0 if the device did not ack
164 * -ETIMEDOUT if an error occurred (while raising the scl line)
165 */
166static int i2c_outb(struct i2c_adapter *i2c_adap, unsigned char c)
167{
168 int i;
169 int sb;
170 int ack;
171 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
172
173 /* assert: scl is low */
174 for (i = 7; i >= 0; i--) {
175 sb = (c >> i) & 1;
176 setsda(adap, sb);
177 udelay((adap->udelay + 1) / 2);
178 if (sclhi(adap) < 0) { /* timed out */
179 bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
180 "timeout at bit #%d\n", (int)c, i);
181 return -ETIMEDOUT;
182 }
183 /* FIXME do arbitration here:
184 * if (sb && !getsda(adap)) -> ouch! Get out of here.
185 *
186 * Report a unique code, so higher level code can retry
187 * the whole (combined) message and *NOT* issue STOP.
188 */
189 scllo(adap);
190 }
191 sdahi(adap);
192 if (sclhi(adap) < 0) { /* timeout */
193 bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
194 "timeout at ack\n", (int)c);
195 return -ETIMEDOUT;
196 }
197
198 /* read ack: SDA should be pulled down by slave, or it may
199 * NAK (usually to report problems with the data we wrote).
200 */
201 ack = !getsda(adap); /* ack: sda is pulled low -> success */
202 bit_dbg(2, &i2c_adap->dev, "i2c_outb: 0x%02x %s\n", (int)c,
203 ack ? "A" : "NA");
204
205 scllo(adap);
206 return ack;
207 /* assert: scl is low (sda undef) */
208}
209
210
211static int i2c_inb(struct i2c_adapter *i2c_adap)
212{
213 /* read byte via i2c port, without start/stop sequence */
214 /* acknowledge is sent in i2c_read. */
215 int i;
216 unsigned char indata = 0;
217 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
218
219 /* assert: scl is low */
220 sdahi(adap);
221 for (i = 0; i < 8; i++) {
222 if (sclhi(adap) < 0) { /* timeout */
223 bit_dbg(1, &i2c_adap->dev, "i2c_inb: timeout at bit "
224 "#%d\n", 7 - i);
225 return -ETIMEDOUT;
226 }
227 indata *= 2;
228 if (getsda(adap))
229 indata |= 0x01;
230 setscl(adap, 0);
231 udelay(i == 7 ? adap->udelay / 2 : adap->udelay);
232 }
233 /* assert: scl is low */
234 return indata;
235}
236
237/*
238 * Sanity check for the adapter hardware - check the reaction of
239 * the bus lines only if it seems to be idle.
240 */
241static int test_bus(struct i2c_adapter *i2c_adap)
242{
243 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
244 const char *name = i2c_adap->name;
245 int scl, sda, ret;
246
247 if (adap->pre_xfer) {
248 ret = adap->pre_xfer(i2c_adap);
249 if (ret < 0)
250 return -ENODEV;
251 }
252
253 if (adap->getscl == NULL)
254 pr_info("%s: Testing SDA only, SCL is not readable\n", name);
255
256 sda = getsda(adap);
257 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
258 if (!scl || !sda) {
259 printk(KERN_WARNING
260 "%s: bus seems to be busy (scl=%d, sda=%d)\n",
261 name, scl, sda);
262 goto bailout;
263 }
264
265 sdalo(adap);
266 sda = getsda(adap);
267 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
268 if (sda) {
269 printk(KERN_WARNING "%s: SDA stuck high!\n", name);
270 goto bailout;
271 }
272 if (!scl) {
273 printk(KERN_WARNING "%s: SCL unexpected low "
274 "while pulling SDA low!\n", name);
275 goto bailout;
276 }
277
278 sdahi(adap);
279 sda = getsda(adap);
280 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
281 if (!sda) {
282 printk(KERN_WARNING "%s: SDA stuck low!\n", name);
283 goto bailout;
284 }
285 if (!scl) {
286 printk(KERN_WARNING "%s: SCL unexpected low "
287 "while pulling SDA high!\n", name);
288 goto bailout;
289 }
290
291 scllo(adap);
292 sda = getsda(adap);
293 scl = (adap->getscl == NULL) ? 0 : getscl(adap);
294 if (scl) {
295 printk(KERN_WARNING "%s: SCL stuck high!\n", name);
296 goto bailout;
297 }
298 if (!sda) {
299 printk(KERN_WARNING "%s: SDA unexpected low "
300 "while pulling SCL low!\n", name);
301 goto bailout;
302 }
303
304 sclhi(adap);
305 sda = getsda(adap);
306 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
307 if (!scl) {
308 printk(KERN_WARNING "%s: SCL stuck low!\n", name);
309 goto bailout;
310 }
311 if (!sda) {
312 printk(KERN_WARNING "%s: SDA unexpected low "
313 "while pulling SCL high!\n", name);
314 goto bailout;
315 }
316
317 if (adap->post_xfer)
318 adap->post_xfer(i2c_adap);
319
320 pr_info("%s: Test OK\n", name);
321 return 0;
322bailout:
323 sdahi(adap);
324 sclhi(adap);
325
326 if (adap->post_xfer)
327 adap->post_xfer(i2c_adap);
328
329 return -ENODEV;
330}
331
332/* ----- Utility functions
333 */
334
335/* try_address tries to contact a chip for a number of
336 * times before it gives up.
337 * return values:
338 * 1 chip answered
339 * 0 chip did not answer
340 * -x transmission error
341 */
342static int try_address(struct i2c_adapter *i2c_adap,
343 unsigned char addr, int retries)
344{
345 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
346 int i, ret = 0;
347
348 for (i = 0; i <= retries; i++) {
349 ret = i2c_outb(i2c_adap, addr);
350 if (ret == 1 || i == retries)
351 break;
352 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
353 i2c_stop(adap);
354 udelay(adap->udelay);
355 yield();
356 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
357 i2c_start(adap);
358 }
359 if (i && ret)
360 bit_dbg(1, &i2c_adap->dev, "Used %d tries to %s client at "
361 "0x%02x: %s\n", i + 1,
362 addr & 1 ? "read from" : "write to", addr >> 1,
363 ret == 1 ? "success" : "failed, timeout?");
364 return ret;
365}
366
367static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
368{
369 const unsigned char *temp = msg->buf;
370 int count = msg->len;
371 unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
372 int retval;
373 int wrcount = 0;
374
375 while (count > 0) {
376 retval = i2c_outb(i2c_adap, *temp);
377
378 /* OK/ACK; or ignored NAK */
379 if ((retval > 0) || (nak_ok && (retval == 0))) {
380 count--;
381 temp++;
382 wrcount++;
383
384 /* A slave NAKing the master means the slave didn't like
385 * something about the data it saw. For example, maybe
386 * the SMBus PEC was wrong.
387 */
388 } else if (retval == 0) {
389 dev_err(&i2c_adap->dev, "sendbytes: NAK bailout.\n");
390 return -EIO;
391
392 /* Timeout; or (someday) lost arbitration
393 *
394 * FIXME Lost ARB implies retrying the transaction from
395 * the first message, after the "winning" master issues
396 * its STOP. As a rule, upper layer code has no reason
397 * to know or care about this ... it is *NOT* an error.
398 */
399 } else {
400 dev_err(&i2c_adap->dev, "sendbytes: error %d\n",
401 retval);
402 return retval;
403 }
404 }
405 return wrcount;
406}
407
408static int acknak(struct i2c_adapter *i2c_adap, int is_ack)
409{
410 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
411
412 /* assert: sda is high */
413 if (is_ack) /* send ack */
414 setsda(adap, 0);
415 udelay((adap->udelay + 1) / 2);
416 if (sclhi(adap) < 0) { /* timeout */
417 dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n");
418 return -ETIMEDOUT;
419 }
420 scllo(adap);
421 return 0;
422}
423
424static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
425{
426 int inval;
427 int rdcount = 0; /* counts bytes read */
428 unsigned char *temp = msg->buf;
429 int count = msg->len;
430 const unsigned flags = msg->flags;
431
432 while (count > 0) {
433 inval = i2c_inb(i2c_adap);
434 if (inval >= 0) {
435 *temp = inval;
436 rdcount++;
437 } else { /* read timed out */
438 break;
439 }
440
441 temp++;
442 count--;
443
444 /* Some SMBus transactions require that we receive the
445 transaction length as the first read byte. */
446 if (rdcount == 1 && (flags & I2C_M_RECV_LEN)) {
447 if (inval <= 0 || inval > I2C_SMBUS_BLOCK_MAX) {
448 if (!(flags & I2C_M_NO_RD_ACK))
449 acknak(i2c_adap, 0);
450 dev_err(&i2c_adap->dev, "readbytes: invalid "
451 "block length (%d)\n", inval);
452 return -EPROTO;
453 }
454 /* The original count value accounts for the extra
455 bytes, that is, either 1 for a regular transaction,
456 or 2 for a PEC transaction. */
457 count += inval;
458 msg->len += inval;
459 }
460
461 bit_dbg(2, &i2c_adap->dev, "readbytes: 0x%02x %s\n",
462 inval,
463 (flags & I2C_M_NO_RD_ACK)
464 ? "(no ack/nak)"
465 : (count ? "A" : "NA"));
466
467 if (!(flags & I2C_M_NO_RD_ACK)) {
468 inval = acknak(i2c_adap, count);
469 if (inval < 0)
470 return inval;
471 }
472 }
473 return rdcount;
474}
475
476/* doAddress initiates the transfer by generating the start condition (in
477 * try_address) and transmits the address in the necessary format to handle
478 * reads, writes as well as 10bit-addresses.
479 * returns:
480 * 0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set
481 * -x an error occurred (like: -ENXIO if the device did not answer, or
482 * -ETIMEDOUT, for example if the lines are stuck...)
483 */
484static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
485{
486 unsigned short flags = msg->flags;
487 unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
488 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
489
490 unsigned char addr;
491 int ret, retries;
492
493 retries = nak_ok ? 0 : i2c_adap->retries;
494
495 if (flags & I2C_M_TEN) {
496 /* a ten bit address */
497 addr = 0xf0 | ((msg->addr >> 7) & 0x06);
498 bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr);
499 /* try extended address code...*/
500 ret = try_address(i2c_adap, addr, retries);
501 if ((ret != 1) && !nak_ok) {
502 dev_err(&i2c_adap->dev,
503 "died at extended address code\n");
504 return -ENXIO;
505 }
506 /* the remaining 8 bit address */
507 ret = i2c_outb(i2c_adap, msg->addr & 0xff);
508 if ((ret != 1) && !nak_ok) {
509 /* the chip did not ack / xmission error occurred */
510 dev_err(&i2c_adap->dev, "died at 2nd address code\n");
511 return -ENXIO;
512 }
513 if (flags & I2C_M_RD) {
514 bit_dbg(3, &i2c_adap->dev, "emitting repeated "
515 "start condition\n");
516 i2c_repstart(adap);
517 /* okay, now switch into reading mode */
518 addr |= 0x01;
519 ret = try_address(i2c_adap, addr, retries);
520 if ((ret != 1) && !nak_ok) {
521 dev_err(&i2c_adap->dev,
522 "died at repeated address code\n");
523 return -EIO;
524 }
525 }
526 } else { /* normal 7bit address */
527 addr = msg->addr << 1;
528 if (flags & I2C_M_RD)
529 addr |= 1;
530 if (flags & I2C_M_REV_DIR_ADDR)
531 addr ^= 1;
532 ret = try_address(i2c_adap, addr, retries);
533 if ((ret != 1) && !nak_ok)
534 return -ENXIO;
535 }
536
537 return 0;
538}
539
540static int bit_xfer(struct i2c_adapter *i2c_adap,
541 struct i2c_msg msgs[], int num)
542{
543 struct i2c_msg *pmsg;
544 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
545 int i, ret;
546 unsigned short nak_ok;
547
548 if (adap->pre_xfer) {
549 ret = adap->pre_xfer(i2c_adap);
550 if (ret < 0)
551 return ret;
552 }
553
554 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
555 i2c_start(adap);
556 for (i = 0; i < num; i++) {
557 pmsg = &msgs[i];
558 nak_ok = pmsg->flags & I2C_M_IGNORE_NAK;
559 if (!(pmsg->flags & I2C_M_NOSTART)) {
560 if (i) {
561 bit_dbg(3, &i2c_adap->dev, "emitting "
562 "repeated start condition\n");
563 i2c_repstart(adap);
564 }
565 ret = bit_doAddress(i2c_adap, pmsg);
566 if ((ret != 0) && !nak_ok) {
567 bit_dbg(1, &i2c_adap->dev, "NAK from "
568 "device addr 0x%02x msg #%d\n",
569 msgs[i].addr, i);
570 goto bailout;
571 }
572 }
573 if (pmsg->flags & I2C_M_RD) {
574 /* read bytes into buffer*/
575 ret = readbytes(i2c_adap, pmsg);
576 if (ret >= 1)
577 bit_dbg(2, &i2c_adap->dev, "read %d byte%s\n",
578 ret, ret == 1 ? "" : "s");
579 if (ret < pmsg->len) {
580 if (ret >= 0)
581 ret = -EIO;
582 goto bailout;
583 }
584 } else {
585 /* write bytes from buffer */
586 ret = sendbytes(i2c_adap, pmsg);
587 if (ret >= 1)
588 bit_dbg(2, &i2c_adap->dev, "wrote %d byte%s\n",
589 ret, ret == 1 ? "" : "s");
590 if (ret < pmsg->len) {
591 if (ret >= 0)
592 ret = -EIO;
593 goto bailout;
594 }
595 }
596 }
597 ret = i;
598
599bailout:
600 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
601 i2c_stop(adap);
602
603 if (adap->post_xfer)
604 adap->post_xfer(i2c_adap);
605 return ret;
606}
607
608static u32 bit_func(struct i2c_adapter *adap)
609{
610 return I2C_FUNC_I2C | I2C_FUNC_NOSTART | I2C_FUNC_SMBUS_EMUL |
611 I2C_FUNC_SMBUS_READ_BLOCK_DATA |
612 I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
613 I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
614}
615
616
617/* -----exported algorithm data: ------------------------------------- */
618
619const struct i2c_algorithm i2c_bit_algo = {
620 .master_xfer = bit_xfer,
621 .functionality = bit_func,
622};
623EXPORT_SYMBOL(i2c_bit_algo);
624
625/*
626 * registering functions to load algorithms at runtime
627 */
628static int __i2c_bit_add_bus(struct i2c_adapter *adap,
629 int (*add_adapter)(struct i2c_adapter *))
630{
631 struct i2c_algo_bit_data *bit_adap = adap->algo_data;
632 int ret;
633
634 if (bit_test) {
635 ret = test_bus(adap);
636 if (bit_test >= 2 && ret < 0)
637 return -ENODEV;
638 }
639
640 /* register new adapter to i2c module... */
641 adap->algo = &i2c_bit_algo;
642 adap->retries = 3;
643
644 ret = add_adapter(adap);
645 if (ret < 0)
646 return ret;
647
648 /* Complain if SCL can't be read */
649 if (bit_adap->getscl == NULL) {
650 dev_warn(&adap->dev, "Not I2C compliant: can't read SCL\n");
651 dev_warn(&adap->dev, "Bus may be unreliable\n");
652 }
653 return 0;
654}
655
656int i2c_bit_add_bus(struct i2c_adapter *adap)
657{
658 return __i2c_bit_add_bus(adap, i2c_add_adapter);
659}
660EXPORT_SYMBOL(i2c_bit_add_bus);
661
662int i2c_bit_add_numbered_bus(struct i2c_adapter *adap)
663{
664 return __i2c_bit_add_bus(adap, i2c_add_numbered_adapter);
665}
666EXPORT_SYMBOL(i2c_bit_add_numbered_bus);
667
668MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
669MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm");
670MODULE_LICENSE("GPL");
1/* -------------------------------------------------------------------------
2 * i2c-algo-bit.c i2c driver algorithms for bit-shift adapters
3 * -------------------------------------------------------------------------
4 * Copyright (C) 1995-2000 Simon G. Vogl
5
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.
10
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.
15
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., 51 Franklin Street, Fifth Floor, Boston,
19 MA 02110-1301 USA.
20 * ------------------------------------------------------------------------- */
21
22/* With some changes from Frodo Looijaard <frodol@dds.nl>, Kyösti Mälkki
23 <kmalkki@cc.hut.fi> and Jean Delvare <khali@linux-fr.org> */
24
25#include <linux/kernel.h>
26#include <linux/module.h>
27#include <linux/delay.h>
28#include <linux/init.h>
29#include <linux/errno.h>
30#include <linux/sched.h>
31#include <linux/i2c.h>
32#include <linux/i2c-algo-bit.h>
33
34
35/* ----- global defines ----------------------------------------------- */
36
37#ifdef DEBUG
38#define bit_dbg(level, dev, format, args...) \
39 do { \
40 if (i2c_debug >= level) \
41 dev_dbg(dev, format, ##args); \
42 } while (0)
43#else
44#define bit_dbg(level, dev, format, args...) \
45 do {} while (0)
46#endif /* DEBUG */
47
48/* ----- global variables --------------------------------------------- */
49
50static int bit_test; /* see if the line-setting functions work */
51module_param(bit_test, int, S_IRUGO);
52MODULE_PARM_DESC(bit_test, "lines testing - 0 off; 1 report; 2 fail if stuck");
53
54#ifdef DEBUG
55static int i2c_debug = 1;
56module_param(i2c_debug, int, S_IRUGO | S_IWUSR);
57MODULE_PARM_DESC(i2c_debug,
58 "debug level - 0 off; 1 normal; 2 verbose; 3 very verbose");
59#endif
60
61/* --- setting states on the bus with the right timing: --------------- */
62
63#define setsda(adap, val) adap->setsda(adap->data, val)
64#define setscl(adap, val) adap->setscl(adap->data, val)
65#define getsda(adap) adap->getsda(adap->data)
66#define getscl(adap) adap->getscl(adap->data)
67
68static inline void sdalo(struct i2c_algo_bit_data *adap)
69{
70 setsda(adap, 0);
71 udelay((adap->udelay + 1) / 2);
72}
73
74static inline void sdahi(struct i2c_algo_bit_data *adap)
75{
76 setsda(adap, 1);
77 udelay((adap->udelay + 1) / 2);
78}
79
80static inline void scllo(struct i2c_algo_bit_data *adap)
81{
82 setscl(adap, 0);
83 udelay(adap->udelay / 2);
84}
85
86/*
87 * Raise scl line, and do checking for delays. This is necessary for slower
88 * devices.
89 */
90static int sclhi(struct i2c_algo_bit_data *adap)
91{
92 unsigned long start;
93
94 setscl(adap, 1);
95
96 /* Not all adapters have scl sense line... */
97 if (!adap->getscl)
98 goto done;
99
100 start = jiffies;
101 while (!getscl(adap)) {
102 /* This hw knows how to read the clock line, so we wait
103 * until it actually gets high. This is safer as some
104 * chips may hold it low ("clock stretching") while they
105 * are processing data internally.
106 */
107 if (time_after(jiffies, start + adap->timeout)) {
108 /* Test one last time, as we may have been preempted
109 * between last check and timeout test.
110 */
111 if (getscl(adap))
112 break;
113 return -ETIMEDOUT;
114 }
115 cpu_relax();
116 }
117#ifdef DEBUG
118 if (jiffies != start && i2c_debug >= 3)
119 pr_debug("i2c-algo-bit: needed %ld jiffies for SCL to go "
120 "high\n", jiffies - start);
121#endif
122
123done:
124 udelay(adap->udelay);
125 return 0;
126}
127
128
129/* --- other auxiliary functions -------------------------------------- */
130static void i2c_start(struct i2c_algo_bit_data *adap)
131{
132 /* assert: scl, sda are high */
133 setsda(adap, 0);
134 udelay(adap->udelay);
135 scllo(adap);
136}
137
138static void i2c_repstart(struct i2c_algo_bit_data *adap)
139{
140 /* assert: scl is low */
141 sdahi(adap);
142 sclhi(adap);
143 setsda(adap, 0);
144 udelay(adap->udelay);
145 scllo(adap);
146}
147
148
149static void i2c_stop(struct i2c_algo_bit_data *adap)
150{
151 /* assert: scl is low */
152 sdalo(adap);
153 sclhi(adap);
154 setsda(adap, 1);
155 udelay(adap->udelay);
156}
157
158
159
160/* send a byte without start cond., look for arbitration,
161 check ackn. from slave */
162/* returns:
163 * 1 if the device acknowledged
164 * 0 if the device did not ack
165 * -ETIMEDOUT if an error occurred (while raising the scl line)
166 */
167static int i2c_outb(struct i2c_adapter *i2c_adap, unsigned char c)
168{
169 int i;
170 int sb;
171 int ack;
172 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
173
174 /* assert: scl is low */
175 for (i = 7; i >= 0; i--) {
176 sb = (c >> i) & 1;
177 setsda(adap, sb);
178 udelay((adap->udelay + 1) / 2);
179 if (sclhi(adap) < 0) { /* timed out */
180 bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
181 "timeout at bit #%d\n", (int)c, i);
182 return -ETIMEDOUT;
183 }
184 /* FIXME do arbitration here:
185 * if (sb && !getsda(adap)) -> ouch! Get out of here.
186 *
187 * Report a unique code, so higher level code can retry
188 * the whole (combined) message and *NOT* issue STOP.
189 */
190 scllo(adap);
191 }
192 sdahi(adap);
193 if (sclhi(adap) < 0) { /* timeout */
194 bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
195 "timeout at ack\n", (int)c);
196 return -ETIMEDOUT;
197 }
198
199 /* read ack: SDA should be pulled down by slave, or it may
200 * NAK (usually to report problems with the data we wrote).
201 */
202 ack = !getsda(adap); /* ack: sda is pulled low -> success */
203 bit_dbg(2, &i2c_adap->dev, "i2c_outb: 0x%02x %s\n", (int)c,
204 ack ? "A" : "NA");
205
206 scllo(adap);
207 return ack;
208 /* assert: scl is low (sda undef) */
209}
210
211
212static int i2c_inb(struct i2c_adapter *i2c_adap)
213{
214 /* read byte via i2c port, without start/stop sequence */
215 /* acknowledge is sent in i2c_read. */
216 int i;
217 unsigned char indata = 0;
218 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
219
220 /* assert: scl is low */
221 sdahi(adap);
222 for (i = 0; i < 8; i++) {
223 if (sclhi(adap) < 0) { /* timeout */
224 bit_dbg(1, &i2c_adap->dev, "i2c_inb: timeout at bit "
225 "#%d\n", 7 - i);
226 return -ETIMEDOUT;
227 }
228 indata *= 2;
229 if (getsda(adap))
230 indata |= 0x01;
231 setscl(adap, 0);
232 udelay(i == 7 ? adap->udelay / 2 : adap->udelay);
233 }
234 /* assert: scl is low */
235 return indata;
236}
237
238/*
239 * Sanity check for the adapter hardware - check the reaction of
240 * the bus lines only if it seems to be idle.
241 */
242static int test_bus(struct i2c_adapter *i2c_adap)
243{
244 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
245 const char *name = i2c_adap->name;
246 int scl, sda, ret;
247
248 if (adap->pre_xfer) {
249 ret = adap->pre_xfer(i2c_adap);
250 if (ret < 0)
251 return -ENODEV;
252 }
253
254 if (adap->getscl == NULL)
255 pr_info("%s: Testing SDA only, SCL is not readable\n", name);
256
257 sda = getsda(adap);
258 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
259 if (!scl || !sda) {
260 printk(KERN_WARNING
261 "%s: bus seems to be busy (scl=%d, sda=%d)\n",
262 name, scl, sda);
263 goto bailout;
264 }
265
266 sdalo(adap);
267 sda = getsda(adap);
268 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
269 if (sda) {
270 printk(KERN_WARNING "%s: SDA stuck high!\n", name);
271 goto bailout;
272 }
273 if (!scl) {
274 printk(KERN_WARNING "%s: SCL unexpected low "
275 "while pulling SDA low!\n", name);
276 goto bailout;
277 }
278
279 sdahi(adap);
280 sda = getsda(adap);
281 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
282 if (!sda) {
283 printk(KERN_WARNING "%s: SDA stuck low!\n", name);
284 goto bailout;
285 }
286 if (!scl) {
287 printk(KERN_WARNING "%s: SCL unexpected low "
288 "while pulling SDA high!\n", name);
289 goto bailout;
290 }
291
292 scllo(adap);
293 sda = getsda(adap);
294 scl = (adap->getscl == NULL) ? 0 : getscl(adap);
295 if (scl) {
296 printk(KERN_WARNING "%s: SCL stuck high!\n", name);
297 goto bailout;
298 }
299 if (!sda) {
300 printk(KERN_WARNING "%s: SDA unexpected low "
301 "while pulling SCL low!\n", name);
302 goto bailout;
303 }
304
305 sclhi(adap);
306 sda = getsda(adap);
307 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
308 if (!scl) {
309 printk(KERN_WARNING "%s: SCL stuck low!\n", name);
310 goto bailout;
311 }
312 if (!sda) {
313 printk(KERN_WARNING "%s: SDA unexpected low "
314 "while pulling SCL high!\n", name);
315 goto bailout;
316 }
317
318 if (adap->post_xfer)
319 adap->post_xfer(i2c_adap);
320
321 pr_info("%s: Test OK\n", name);
322 return 0;
323bailout:
324 sdahi(adap);
325 sclhi(adap);
326
327 if (adap->post_xfer)
328 adap->post_xfer(i2c_adap);
329
330 return -ENODEV;
331}
332
333/* ----- Utility functions
334 */
335
336/* try_address tries to contact a chip for a number of
337 * times before it gives up.
338 * return values:
339 * 1 chip answered
340 * 0 chip did not answer
341 * -x transmission error
342 */
343static int try_address(struct i2c_adapter *i2c_adap,
344 unsigned char addr, int retries)
345{
346 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
347 int i, ret = 0;
348
349 for (i = 0; i <= retries; i++) {
350 ret = i2c_outb(i2c_adap, addr);
351 if (ret == 1 || i == retries)
352 break;
353 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
354 i2c_stop(adap);
355 udelay(adap->udelay);
356 yield();
357 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
358 i2c_start(adap);
359 }
360 if (i && ret)
361 bit_dbg(1, &i2c_adap->dev, "Used %d tries to %s client at "
362 "0x%02x: %s\n", i + 1,
363 addr & 1 ? "read from" : "write to", addr >> 1,
364 ret == 1 ? "success" : "failed, timeout?");
365 return ret;
366}
367
368static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
369{
370 const unsigned char *temp = msg->buf;
371 int count = msg->len;
372 unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
373 int retval;
374 int wrcount = 0;
375
376 while (count > 0) {
377 retval = i2c_outb(i2c_adap, *temp);
378
379 /* OK/ACK; or ignored NAK */
380 if ((retval > 0) || (nak_ok && (retval == 0))) {
381 count--;
382 temp++;
383 wrcount++;
384
385 /* A slave NAKing the master means the slave didn't like
386 * something about the data it saw. For example, maybe
387 * the SMBus PEC was wrong.
388 */
389 } else if (retval == 0) {
390 dev_err(&i2c_adap->dev, "sendbytes: NAK bailout.\n");
391 return -EIO;
392
393 /* Timeout; or (someday) lost arbitration
394 *
395 * FIXME Lost ARB implies retrying the transaction from
396 * the first message, after the "winning" master issues
397 * its STOP. As a rule, upper layer code has no reason
398 * to know or care about this ... it is *NOT* an error.
399 */
400 } else {
401 dev_err(&i2c_adap->dev, "sendbytes: error %d\n",
402 retval);
403 return retval;
404 }
405 }
406 return wrcount;
407}
408
409static int acknak(struct i2c_adapter *i2c_adap, int is_ack)
410{
411 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
412
413 /* assert: sda is high */
414 if (is_ack) /* send ack */
415 setsda(adap, 0);
416 udelay((adap->udelay + 1) / 2);
417 if (sclhi(adap) < 0) { /* timeout */
418 dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n");
419 return -ETIMEDOUT;
420 }
421 scllo(adap);
422 return 0;
423}
424
425static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
426{
427 int inval;
428 int rdcount = 0; /* counts bytes read */
429 unsigned char *temp = msg->buf;
430 int count = msg->len;
431 const unsigned flags = msg->flags;
432
433 while (count > 0) {
434 inval = i2c_inb(i2c_adap);
435 if (inval >= 0) {
436 *temp = inval;
437 rdcount++;
438 } else { /* read timed out */
439 break;
440 }
441
442 temp++;
443 count--;
444
445 /* Some SMBus transactions require that we receive the
446 transaction length as the first read byte. */
447 if (rdcount == 1 && (flags & I2C_M_RECV_LEN)) {
448 if (inval <= 0 || inval > I2C_SMBUS_BLOCK_MAX) {
449 if (!(flags & I2C_M_NO_RD_ACK))
450 acknak(i2c_adap, 0);
451 dev_err(&i2c_adap->dev, "readbytes: invalid "
452 "block length (%d)\n", inval);
453 return -EPROTO;
454 }
455 /* The original count value accounts for the extra
456 bytes, that is, either 1 for a regular transaction,
457 or 2 for a PEC transaction. */
458 count += inval;
459 msg->len += inval;
460 }
461
462 bit_dbg(2, &i2c_adap->dev, "readbytes: 0x%02x %s\n",
463 inval,
464 (flags & I2C_M_NO_RD_ACK)
465 ? "(no ack/nak)"
466 : (count ? "A" : "NA"));
467
468 if (!(flags & I2C_M_NO_RD_ACK)) {
469 inval = acknak(i2c_adap, count);
470 if (inval < 0)
471 return inval;
472 }
473 }
474 return rdcount;
475}
476
477/* doAddress initiates the transfer by generating the start condition (in
478 * try_address) and transmits the address in the necessary format to handle
479 * reads, writes as well as 10bit-addresses.
480 * returns:
481 * 0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set
482 * -x an error occurred (like: -ENXIO if the device did not answer, or
483 * -ETIMEDOUT, for example if the lines are stuck...)
484 */
485static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
486{
487 unsigned short flags = msg->flags;
488 unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
489 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
490
491 unsigned char addr;
492 int ret, retries;
493
494 retries = nak_ok ? 0 : i2c_adap->retries;
495
496 if (flags & I2C_M_TEN) {
497 /* a ten bit address */
498 addr = 0xf0 | ((msg->addr >> 7) & 0x06);
499 bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr);
500 /* try extended address code...*/
501 ret = try_address(i2c_adap, addr, retries);
502 if ((ret != 1) && !nak_ok) {
503 dev_err(&i2c_adap->dev,
504 "died at extended address code\n");
505 return -ENXIO;
506 }
507 /* the remaining 8 bit address */
508 ret = i2c_outb(i2c_adap, msg->addr & 0xff);
509 if ((ret != 1) && !nak_ok) {
510 /* the chip did not ack / xmission error occurred */
511 dev_err(&i2c_adap->dev, "died at 2nd address code\n");
512 return -ENXIO;
513 }
514 if (flags & I2C_M_RD) {
515 bit_dbg(3, &i2c_adap->dev, "emitting repeated "
516 "start condition\n");
517 i2c_repstart(adap);
518 /* okay, now switch into reading mode */
519 addr |= 0x01;
520 ret = try_address(i2c_adap, addr, retries);
521 if ((ret != 1) && !nak_ok) {
522 dev_err(&i2c_adap->dev,
523 "died at repeated address code\n");
524 return -EIO;
525 }
526 }
527 } else { /* normal 7bit address */
528 addr = msg->addr << 1;
529 if (flags & I2C_M_RD)
530 addr |= 1;
531 if (flags & I2C_M_REV_DIR_ADDR)
532 addr ^= 1;
533 ret = try_address(i2c_adap, addr, retries);
534 if ((ret != 1) && !nak_ok)
535 return -ENXIO;
536 }
537
538 return 0;
539}
540
541static int bit_xfer(struct i2c_adapter *i2c_adap,
542 struct i2c_msg msgs[], int num)
543{
544 struct i2c_msg *pmsg;
545 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
546 int i, ret;
547 unsigned short nak_ok;
548
549 if (adap->pre_xfer) {
550 ret = adap->pre_xfer(i2c_adap);
551 if (ret < 0)
552 return ret;
553 }
554
555 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
556 i2c_start(adap);
557 for (i = 0; i < num; i++) {
558 pmsg = &msgs[i];
559 nak_ok = pmsg->flags & I2C_M_IGNORE_NAK;
560 if (!(pmsg->flags & I2C_M_NOSTART)) {
561 if (i) {
562 bit_dbg(3, &i2c_adap->dev, "emitting "
563 "repeated start condition\n");
564 i2c_repstart(adap);
565 }
566 ret = bit_doAddress(i2c_adap, pmsg);
567 if ((ret != 0) && !nak_ok) {
568 bit_dbg(1, &i2c_adap->dev, "NAK from "
569 "device addr 0x%02x msg #%d\n",
570 msgs[i].addr, i);
571 goto bailout;
572 }
573 }
574 if (pmsg->flags & I2C_M_RD) {
575 /* read bytes into buffer*/
576 ret = readbytes(i2c_adap, pmsg);
577 if (ret >= 1)
578 bit_dbg(2, &i2c_adap->dev, "read %d byte%s\n",
579 ret, ret == 1 ? "" : "s");
580 if (ret < pmsg->len) {
581 if (ret >= 0)
582 ret = -EIO;
583 goto bailout;
584 }
585 } else {
586 /* write bytes from buffer */
587 ret = sendbytes(i2c_adap, pmsg);
588 if (ret >= 1)
589 bit_dbg(2, &i2c_adap->dev, "wrote %d byte%s\n",
590 ret, ret == 1 ? "" : "s");
591 if (ret < pmsg->len) {
592 if (ret >= 0)
593 ret = -EIO;
594 goto bailout;
595 }
596 }
597 }
598 ret = i;
599
600bailout:
601 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
602 i2c_stop(adap);
603
604 if (adap->post_xfer)
605 adap->post_xfer(i2c_adap);
606 return ret;
607}
608
609static u32 bit_func(struct i2c_adapter *adap)
610{
611 return I2C_FUNC_I2C | I2C_FUNC_NOSTART | I2C_FUNC_SMBUS_EMUL |
612 I2C_FUNC_SMBUS_READ_BLOCK_DATA |
613 I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
614 I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
615}
616
617
618/* -----exported algorithm data: ------------------------------------- */
619
620const struct i2c_algorithm i2c_bit_algo = {
621 .master_xfer = bit_xfer,
622 .functionality = bit_func,
623};
624EXPORT_SYMBOL(i2c_bit_algo);
625
626/*
627 * registering functions to load algorithms at runtime
628 */
629static int __i2c_bit_add_bus(struct i2c_adapter *adap,
630 int (*add_adapter)(struct i2c_adapter *))
631{
632 struct i2c_algo_bit_data *bit_adap = adap->algo_data;
633 int ret;
634
635 if (bit_test) {
636 ret = test_bus(adap);
637 if (bit_test >= 2 && ret < 0)
638 return -ENODEV;
639 }
640
641 /* register new adapter to i2c module... */
642 adap->algo = &i2c_bit_algo;
643 adap->retries = 3;
644
645 ret = add_adapter(adap);
646 if (ret < 0)
647 return ret;
648
649 /* Complain if SCL can't be read */
650 if (bit_adap->getscl == NULL) {
651 dev_warn(&adap->dev, "Not I2C compliant: can't read SCL\n");
652 dev_warn(&adap->dev, "Bus may be unreliable\n");
653 }
654 return 0;
655}
656
657int i2c_bit_add_bus(struct i2c_adapter *adap)
658{
659 return __i2c_bit_add_bus(adap, i2c_add_adapter);
660}
661EXPORT_SYMBOL(i2c_bit_add_bus);
662
663int i2c_bit_add_numbered_bus(struct i2c_adapter *adap)
664{
665 return __i2c_bit_add_bus(adap, i2c_add_numbered_adapter);
666}
667EXPORT_SYMBOL(i2c_bit_add_numbered_bus);
668
669MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
670MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm");
671MODULE_LICENSE("GPL");