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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
17/* With some changes from Frodo Looijaard <frodol@dds.nl>, Kyösti Mälkki
18 <kmalkki@cc.hut.fi> and Jean Delvare <jdelvare@suse.de> */
19
20#include <linux/kernel.h>
21#include <linux/module.h>
22#include <linux/delay.h>
23#include <linux/errno.h>
24#include <linux/sched.h>
25#include <linux/i2c.h>
26#include <linux/i2c-algo-bit.h>
27
28
29/* ----- global defines ----------------------------------------------- */
30
31#ifdef DEBUG
32#define bit_dbg(level, dev, format, args...) \
33 do { \
34 if (i2c_debug >= level) \
35 dev_dbg(dev, format, ##args); \
36 } while (0)
37#else
38#define bit_dbg(level, dev, format, args...) \
39 do {} while (0)
40#endif /* DEBUG */
41
42/* ----- global variables --------------------------------------------- */
43
44static int bit_test; /* see if the line-setting functions work */
45module_param(bit_test, int, S_IRUGO);
46MODULE_PARM_DESC(bit_test, "lines testing - 0 off; 1 report; 2 fail if stuck");
47
48#ifdef DEBUG
49static int i2c_debug = 1;
50module_param(i2c_debug, int, S_IRUGO | S_IWUSR);
51MODULE_PARM_DESC(i2c_debug,
52 "debug level - 0 off; 1 normal; 2 verbose; 3 very verbose");
53#endif
54
55/* --- setting states on the bus with the right timing: --------------- */
56
57#define setsda(adap, val) adap->setsda(adap->data, val)
58#define setscl(adap, val) adap->setscl(adap->data, val)
59#define getsda(adap) adap->getsda(adap->data)
60#define getscl(adap) adap->getscl(adap->data)
61
62static inline void sdalo(struct i2c_algo_bit_data *adap)
63{
64 setsda(adap, 0);
65 udelay((adap->udelay + 1) / 2);
66}
67
68static inline void sdahi(struct i2c_algo_bit_data *adap)
69{
70 setsda(adap, 1);
71 udelay((adap->udelay + 1) / 2);
72}
73
74static inline void scllo(struct i2c_algo_bit_data *adap)
75{
76 setscl(adap, 0);
77 udelay(adap->udelay / 2);
78}
79
80/*
81 * Raise scl line, and do checking for delays. This is necessary for slower
82 * devices.
83 */
84static int sclhi(struct i2c_algo_bit_data *adap)
85{
86 unsigned long start;
87
88 setscl(adap, 1);
89
90 /* Not all adapters have scl sense line... */
91 if (!adap->getscl)
92 goto done;
93
94 start = jiffies;
95 while (!getscl(adap)) {
96 /* This hw knows how to read the clock line, so we wait
97 * until it actually gets high. This is safer as some
98 * chips may hold it low ("clock stretching") while they
99 * are processing data internally.
100 */
101 if (time_after(jiffies, start + adap->timeout)) {
102 /* Test one last time, as we may have been preempted
103 * between last check and timeout test.
104 */
105 if (getscl(adap))
106 break;
107 return -ETIMEDOUT;
108 }
109 cpu_relax();
110 }
111#ifdef DEBUG
112 if (jiffies != start && i2c_debug >= 3)
113 pr_debug("i2c-algo-bit: needed %ld jiffies for SCL to go "
114 "high\n", jiffies - start);
115#endif
116
117done:
118 udelay(adap->udelay);
119 return 0;
120}
121
122
123/* --- other auxiliary functions -------------------------------------- */
124static void i2c_start(struct i2c_algo_bit_data *adap)
125{
126 /* assert: scl, sda are high */
127 setsda(adap, 0);
128 udelay(adap->udelay);
129 scllo(adap);
130}
131
132static void i2c_repstart(struct i2c_algo_bit_data *adap)
133{
134 /* assert: scl is low */
135 sdahi(adap);
136 sclhi(adap);
137 setsda(adap, 0);
138 udelay(adap->udelay);
139 scllo(adap);
140}
141
142
143static void i2c_stop(struct i2c_algo_bit_data *adap)
144{
145 /* assert: scl is low */
146 sdalo(adap);
147 sclhi(adap);
148 setsda(adap, 1);
149 udelay(adap->udelay);
150}
151
152
153
154/* send a byte without start cond., look for arbitration,
155 check ackn. from slave */
156/* returns:
157 * 1 if the device acknowledged
158 * 0 if the device did not ack
159 * -ETIMEDOUT if an error occurred (while raising the scl line)
160 */
161static int i2c_outb(struct i2c_adapter *i2c_adap, unsigned char c)
162{
163 int i;
164 int sb;
165 int ack;
166 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
167
168 /* assert: scl is low */
169 for (i = 7; i >= 0; i--) {
170 sb = (c >> i) & 1;
171 setsda(adap, sb);
172 udelay((adap->udelay + 1) / 2);
173 if (sclhi(adap) < 0) { /* timed out */
174 bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
175 "timeout at bit #%d\n", (int)c, i);
176 return -ETIMEDOUT;
177 }
178 /* FIXME do arbitration here:
179 * if (sb && !getsda(adap)) -> ouch! Get out of here.
180 *
181 * Report a unique code, so higher level code can retry
182 * the whole (combined) message and *NOT* issue STOP.
183 */
184 scllo(adap);
185 }
186 sdahi(adap);
187 if (sclhi(adap) < 0) { /* timeout */
188 bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
189 "timeout at ack\n", (int)c);
190 return -ETIMEDOUT;
191 }
192
193 /* read ack: SDA should be pulled down by slave, or it may
194 * NAK (usually to report problems with the data we wrote).
195 */
196 ack = !getsda(adap); /* ack: sda is pulled low -> success */
197 bit_dbg(2, &i2c_adap->dev, "i2c_outb: 0x%02x %s\n", (int)c,
198 ack ? "A" : "NA");
199
200 scllo(adap);
201 return ack;
202 /* assert: scl is low (sda undef) */
203}
204
205
206static int i2c_inb(struct i2c_adapter *i2c_adap)
207{
208 /* read byte via i2c port, without start/stop sequence */
209 /* acknowledge is sent in i2c_read. */
210 int i;
211 unsigned char indata = 0;
212 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
213
214 /* assert: scl is low */
215 sdahi(adap);
216 for (i = 0; i < 8; i++) {
217 if (sclhi(adap) < 0) { /* timeout */
218 bit_dbg(1, &i2c_adap->dev, "i2c_inb: timeout at bit "
219 "#%d\n", 7 - i);
220 return -ETIMEDOUT;
221 }
222 indata *= 2;
223 if (getsda(adap))
224 indata |= 0x01;
225 setscl(adap, 0);
226 udelay(i == 7 ? adap->udelay / 2 : adap->udelay);
227 }
228 /* assert: scl is low */
229 return indata;
230}
231
232/*
233 * Sanity check for the adapter hardware - check the reaction of
234 * the bus lines only if it seems to be idle.
235 */
236static int test_bus(struct i2c_adapter *i2c_adap)
237{
238 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
239 const char *name = i2c_adap->name;
240 int scl, sda, ret;
241
242 if (adap->pre_xfer) {
243 ret = adap->pre_xfer(i2c_adap);
244 if (ret < 0)
245 return -ENODEV;
246 }
247
248 if (adap->getscl == NULL)
249 pr_info("%s: Testing SDA only, SCL is not readable\n", name);
250
251 sda = getsda(adap);
252 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
253 if (!scl || !sda) {
254 printk(KERN_WARNING
255 "%s: bus seems to be busy (scl=%d, sda=%d)\n",
256 name, scl, sda);
257 goto bailout;
258 }
259
260 sdalo(adap);
261 sda = getsda(adap);
262 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
263 if (sda) {
264 printk(KERN_WARNING "%s: SDA stuck high!\n", name);
265 goto bailout;
266 }
267 if (!scl) {
268 printk(KERN_WARNING "%s: SCL unexpected low "
269 "while pulling SDA low!\n", name);
270 goto bailout;
271 }
272
273 sdahi(adap);
274 sda = getsda(adap);
275 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
276 if (!sda) {
277 printk(KERN_WARNING "%s: SDA stuck low!\n", name);
278 goto bailout;
279 }
280 if (!scl) {
281 printk(KERN_WARNING "%s: SCL unexpected low "
282 "while pulling SDA high!\n", name);
283 goto bailout;
284 }
285
286 scllo(adap);
287 sda = getsda(adap);
288 scl = (adap->getscl == NULL) ? 0 : getscl(adap);
289 if (scl) {
290 printk(KERN_WARNING "%s: SCL stuck high!\n", name);
291 goto bailout;
292 }
293 if (!sda) {
294 printk(KERN_WARNING "%s: SDA unexpected low "
295 "while pulling SCL low!\n", name);
296 goto bailout;
297 }
298
299 sclhi(adap);
300 sda = getsda(adap);
301 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
302 if (!scl) {
303 printk(KERN_WARNING "%s: SCL stuck low!\n", name);
304 goto bailout;
305 }
306 if (!sda) {
307 printk(KERN_WARNING "%s: SDA unexpected low "
308 "while pulling SCL high!\n", name);
309 goto bailout;
310 }
311
312 if (adap->post_xfer)
313 adap->post_xfer(i2c_adap);
314
315 pr_info("%s: Test OK\n", name);
316 return 0;
317bailout:
318 sdahi(adap);
319 sclhi(adap);
320
321 if (adap->post_xfer)
322 adap->post_xfer(i2c_adap);
323
324 return -ENODEV;
325}
326
327/* ----- Utility functions
328 */
329
330/* try_address tries to contact a chip for a number of
331 * times before it gives up.
332 * return values:
333 * 1 chip answered
334 * 0 chip did not answer
335 * -x transmission error
336 */
337static int try_address(struct i2c_adapter *i2c_adap,
338 unsigned char addr, int retries)
339{
340 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
341 int i, ret = 0;
342
343 for (i = 0; i <= retries; i++) {
344 ret = i2c_outb(i2c_adap, addr);
345 if (ret == 1 || i == retries)
346 break;
347 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
348 i2c_stop(adap);
349 udelay(adap->udelay);
350 yield();
351 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
352 i2c_start(adap);
353 }
354 if (i && ret)
355 bit_dbg(1, &i2c_adap->dev, "Used %d tries to %s client at "
356 "0x%02x: %s\n", i + 1,
357 addr & 1 ? "read from" : "write to", addr >> 1,
358 ret == 1 ? "success" : "failed, timeout?");
359 return ret;
360}
361
362static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
363{
364 const unsigned char *temp = msg->buf;
365 int count = msg->len;
366 unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
367 int retval;
368 int wrcount = 0;
369
370 while (count > 0) {
371 retval = i2c_outb(i2c_adap, *temp);
372
373 /* OK/ACK; or ignored NAK */
374 if ((retval > 0) || (nak_ok && (retval == 0))) {
375 count--;
376 temp++;
377 wrcount++;
378
379 /* A slave NAKing the master means the slave didn't like
380 * something about the data it saw. For example, maybe
381 * the SMBus PEC was wrong.
382 */
383 } else if (retval == 0) {
384 dev_err(&i2c_adap->dev, "sendbytes: NAK bailout.\n");
385 return -EIO;
386
387 /* Timeout; or (someday) lost arbitration
388 *
389 * FIXME Lost ARB implies retrying the transaction from
390 * the first message, after the "winning" master issues
391 * its STOP. As a rule, upper layer code has no reason
392 * to know or care about this ... it is *NOT* an error.
393 */
394 } else {
395 dev_err(&i2c_adap->dev, "sendbytes: error %d\n",
396 retval);
397 return retval;
398 }
399 }
400 return wrcount;
401}
402
403static int acknak(struct i2c_adapter *i2c_adap, int is_ack)
404{
405 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
406
407 /* assert: sda is high */
408 if (is_ack) /* send ack */
409 setsda(adap, 0);
410 udelay((adap->udelay + 1) / 2);
411 if (sclhi(adap) < 0) { /* timeout */
412 dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n");
413 return -ETIMEDOUT;
414 }
415 scllo(adap);
416 return 0;
417}
418
419static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
420{
421 int inval;
422 int rdcount = 0; /* counts bytes read */
423 unsigned char *temp = msg->buf;
424 int count = msg->len;
425 const unsigned flags = msg->flags;
426
427 while (count > 0) {
428 inval = i2c_inb(i2c_adap);
429 if (inval >= 0) {
430 *temp = inval;
431 rdcount++;
432 } else { /* read timed out */
433 break;
434 }
435
436 temp++;
437 count--;
438
439 /* Some SMBus transactions require that we receive the
440 transaction length as the first read byte. */
441 if (rdcount == 1 && (flags & I2C_M_RECV_LEN)) {
442 if (inval <= 0 || inval > I2C_SMBUS_BLOCK_MAX) {
443 if (!(flags & I2C_M_NO_RD_ACK))
444 acknak(i2c_adap, 0);
445 dev_err(&i2c_adap->dev, "readbytes: invalid "
446 "block length (%d)\n", inval);
447 return -EPROTO;
448 }
449 /* The original count value accounts for the extra
450 bytes, that is, either 1 for a regular transaction,
451 or 2 for a PEC transaction. */
452 count += inval;
453 msg->len += inval;
454 }
455
456 bit_dbg(2, &i2c_adap->dev, "readbytes: 0x%02x %s\n",
457 inval,
458 (flags & I2C_M_NO_RD_ACK)
459 ? "(no ack/nak)"
460 : (count ? "A" : "NA"));
461
462 if (!(flags & I2C_M_NO_RD_ACK)) {
463 inval = acknak(i2c_adap, count);
464 if (inval < 0)
465 return inval;
466 }
467 }
468 return rdcount;
469}
470
471/* doAddress initiates the transfer by generating the start condition (in
472 * try_address) and transmits the address in the necessary format to handle
473 * reads, writes as well as 10bit-addresses.
474 * returns:
475 * 0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set
476 * -x an error occurred (like: -ENXIO if the device did not answer, or
477 * -ETIMEDOUT, for example if the lines are stuck...)
478 */
479static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
480{
481 unsigned short flags = msg->flags;
482 unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
483 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
484
485 unsigned char addr;
486 int ret, retries;
487
488 retries = nak_ok ? 0 : i2c_adap->retries;
489
490 if (flags & I2C_M_TEN) {
491 /* a ten bit address */
492 addr = 0xf0 | ((msg->addr >> 7) & 0x06);
493 bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr);
494 /* try extended address code...*/
495 ret = try_address(i2c_adap, addr, retries);
496 if ((ret != 1) && !nak_ok) {
497 dev_err(&i2c_adap->dev,
498 "died at extended address code\n");
499 return -ENXIO;
500 }
501 /* the remaining 8 bit address */
502 ret = i2c_outb(i2c_adap, msg->addr & 0xff);
503 if ((ret != 1) && !nak_ok) {
504 /* the chip did not ack / xmission error occurred */
505 dev_err(&i2c_adap->dev, "died at 2nd address code\n");
506 return -ENXIO;
507 }
508 if (flags & I2C_M_RD) {
509 bit_dbg(3, &i2c_adap->dev, "emitting repeated "
510 "start condition\n");
511 i2c_repstart(adap);
512 /* okay, now switch into reading mode */
513 addr |= 0x01;
514 ret = try_address(i2c_adap, addr, retries);
515 if ((ret != 1) && !nak_ok) {
516 dev_err(&i2c_adap->dev,
517 "died at repeated address code\n");
518 return -EIO;
519 }
520 }
521 } else { /* normal 7bit address */
522 addr = msg->addr << 1;
523 if (flags & I2C_M_RD)
524 addr |= 1;
525 if (flags & I2C_M_REV_DIR_ADDR)
526 addr ^= 1;
527 ret = try_address(i2c_adap, addr, retries);
528 if ((ret != 1) && !nak_ok)
529 return -ENXIO;
530 }
531
532 return 0;
533}
534
535static int bit_xfer(struct i2c_adapter *i2c_adap,
536 struct i2c_msg msgs[], int num)
537{
538 struct i2c_msg *pmsg;
539 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
540 int i, ret;
541 unsigned short nak_ok;
542
543 if (adap->pre_xfer) {
544 ret = adap->pre_xfer(i2c_adap);
545 if (ret < 0)
546 return ret;
547 }
548
549 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
550 i2c_start(adap);
551 for (i = 0; i < num; i++) {
552 pmsg = &msgs[i];
553 nak_ok = pmsg->flags & I2C_M_IGNORE_NAK;
554 if (!(pmsg->flags & I2C_M_NOSTART)) {
555 if (i) {
556 bit_dbg(3, &i2c_adap->dev, "emitting "
557 "repeated start condition\n");
558 i2c_repstart(adap);
559 }
560 ret = bit_doAddress(i2c_adap, pmsg);
561 if ((ret != 0) && !nak_ok) {
562 bit_dbg(1, &i2c_adap->dev, "NAK from "
563 "device addr 0x%02x msg #%d\n",
564 msgs[i].addr, i);
565 goto bailout;
566 }
567 }
568 if (pmsg->flags & I2C_M_RD) {
569 /* read bytes into buffer*/
570 ret = readbytes(i2c_adap, pmsg);
571 if (ret >= 1)
572 bit_dbg(2, &i2c_adap->dev, "read %d byte%s\n",
573 ret, ret == 1 ? "" : "s");
574 if (ret < pmsg->len) {
575 if (ret >= 0)
576 ret = -EIO;
577 goto bailout;
578 }
579 } else {
580 /* write bytes from buffer */
581 ret = sendbytes(i2c_adap, pmsg);
582 if (ret >= 1)
583 bit_dbg(2, &i2c_adap->dev, "wrote %d byte%s\n",
584 ret, ret == 1 ? "" : "s");
585 if (ret < pmsg->len) {
586 if (ret >= 0)
587 ret = -EIO;
588 goto bailout;
589 }
590 }
591 }
592 ret = i;
593
594bailout:
595 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
596 i2c_stop(adap);
597
598 if (adap->post_xfer)
599 adap->post_xfer(i2c_adap);
600 return ret;
601}
602
603static u32 bit_func(struct i2c_adapter *adap)
604{
605 return I2C_FUNC_I2C | I2C_FUNC_NOSTART | I2C_FUNC_SMBUS_EMUL |
606 I2C_FUNC_SMBUS_READ_BLOCK_DATA |
607 I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
608 I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
609}
610
611
612/* -----exported algorithm data: ------------------------------------- */
613
614const struct i2c_algorithm i2c_bit_algo = {
615 .master_xfer = bit_xfer,
616 .functionality = bit_func,
617};
618EXPORT_SYMBOL(i2c_bit_algo);
619
620const struct i2c_adapter_quirks i2c_bit_quirk_no_clk_stretch = {
621 .flags = I2C_AQ_NO_CLK_STRETCH,
622};
623
624/*
625 * registering functions to load algorithms at runtime
626 */
627static int __i2c_bit_add_bus(struct i2c_adapter *adap,
628 int (*add_adapter)(struct i2c_adapter *))
629{
630 struct i2c_algo_bit_data *bit_adap = adap->algo_data;
631 int ret;
632
633 if (bit_test) {
634 ret = test_bus(adap);
635 if (bit_test >= 2 && ret < 0)
636 return -ENODEV;
637 }
638
639 /* register new adapter to i2c module... */
640 adap->algo = &i2c_bit_algo;
641 adap->retries = 3;
642 if (bit_adap->getscl == NULL)
643 adap->quirks = &i2c_bit_quirk_no_clk_stretch;
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");
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");