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1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * i2c-algo-bit.c: i2c driver algorithms for bit-shift adapters
4 *
5 * Copyright (C) 1995-2000 Simon G. Vogl
6 *
7 * With some changes from Frodo Looijaard <frodol@dds.nl>, Kyösti Mälkki
8 * <kmalkki@cc.hut.fi> and Jean Delvare <jdelvare@suse.de>
9 */
10
11#include <linux/kernel.h>
12#include <linux/module.h>
13#include <linux/delay.h>
14#include <linux/errno.h>
15#include <linux/sched.h>
16#include <linux/i2c.h>
17#include <linux/i2c-algo-bit.h>
18
19
20/* ----- global defines ----------------------------------------------- */
21
22#ifdef DEBUG
23#define bit_dbg(level, dev, format, args...) \
24 do { \
25 if (i2c_debug >= level) \
26 dev_dbg(dev, format, ##args); \
27 } while (0)
28#else
29#define bit_dbg(level, dev, format, args...) \
30 do {} while (0)
31#endif /* DEBUG */
32
33/* ----- global variables --------------------------------------------- */
34
35static int bit_test; /* see if the line-setting functions work */
36module_param(bit_test, int, S_IRUGO);
37MODULE_PARM_DESC(bit_test, "lines testing - 0 off; 1 report; 2 fail if stuck");
38
39#ifdef DEBUG
40static int i2c_debug = 1;
41module_param(i2c_debug, int, S_IRUGO | S_IWUSR);
42MODULE_PARM_DESC(i2c_debug,
43 "debug level - 0 off; 1 normal; 2 verbose; 3 very verbose");
44#endif
45
46/* --- setting states on the bus with the right timing: --------------- */
47
48#define setsda(adap, val) adap->setsda(adap->data, val)
49#define setscl(adap, val) adap->setscl(adap->data, val)
50#define getsda(adap) adap->getsda(adap->data)
51#define getscl(adap) adap->getscl(adap->data)
52
53static inline void sdalo(struct i2c_algo_bit_data *adap)
54{
55 setsda(adap, 0);
56 udelay((adap->udelay + 1) / 2);
57}
58
59static inline void sdahi(struct i2c_algo_bit_data *adap)
60{
61 setsda(adap, 1);
62 udelay((adap->udelay + 1) / 2);
63}
64
65static inline void scllo(struct i2c_algo_bit_data *adap)
66{
67 setscl(adap, 0);
68 udelay(adap->udelay / 2);
69}
70
71/*
72 * Raise scl line, and do checking for delays. This is necessary for slower
73 * devices.
74 */
75static int sclhi(struct i2c_algo_bit_data *adap)
76{
77 unsigned long start;
78
79 setscl(adap, 1);
80
81 /* Not all adapters have scl sense line... */
82 if (!adap->getscl)
83 goto done;
84
85 start = jiffies;
86 while (!getscl(adap)) {
87 /* This hw knows how to read the clock line, so we wait
88 * until it actually gets high. This is safer as some
89 * chips may hold it low ("clock stretching") while they
90 * are processing data internally.
91 */
92 if (time_after(jiffies, start + adap->timeout)) {
93 /* Test one last time, as we may have been preempted
94 * between last check and timeout test.
95 */
96 if (getscl(adap))
97 break;
98 return -ETIMEDOUT;
99 }
100 cpu_relax();
101 }
102#ifdef DEBUG
103 if (jiffies != start && i2c_debug >= 3)
104 pr_debug("i2c-algo-bit: needed %ld jiffies for SCL to go high\n",
105 jiffies - start);
106#endif
107
108done:
109 udelay(adap->udelay);
110 return 0;
111}
112
113
114/* --- other auxiliary functions -------------------------------------- */
115static void i2c_start(struct i2c_algo_bit_data *adap)
116{
117 /* assert: scl, sda are high */
118 setsda(adap, 0);
119 udelay(adap->udelay);
120 scllo(adap);
121}
122
123static void i2c_repstart(struct i2c_algo_bit_data *adap)
124{
125 /* assert: scl is low */
126 sdahi(adap);
127 sclhi(adap);
128 setsda(adap, 0);
129 udelay(adap->udelay);
130 scllo(adap);
131}
132
133
134static void i2c_stop(struct i2c_algo_bit_data *adap)
135{
136 /* assert: scl is low */
137 sdalo(adap);
138 sclhi(adap);
139 setsda(adap, 1);
140 udelay(adap->udelay);
141}
142
143
144
145/* send a byte without start cond., look for arbitration,
146 check ackn. from slave */
147/* returns:
148 * 1 if the device acknowledged
149 * 0 if the device did not ack
150 * -ETIMEDOUT if an error occurred (while raising the scl line)
151 */
152static int i2c_outb(struct i2c_adapter *i2c_adap, unsigned char c)
153{
154 int i;
155 int sb;
156 int ack;
157 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
158
159 /* assert: scl is low */
160 for (i = 7; i >= 0; i--) {
161 sb = (c >> i) & 1;
162 setsda(adap, sb);
163 udelay((adap->udelay + 1) / 2);
164 if (sclhi(adap) < 0) { /* timed out */
165 bit_dbg(1, &i2c_adap->dev,
166 "i2c_outb: 0x%02x, timeout at bit #%d\n",
167 (int)c, i);
168 return -ETIMEDOUT;
169 }
170 /* FIXME do arbitration here:
171 * if (sb && !getsda(adap)) -> ouch! Get out of here.
172 *
173 * Report a unique code, so higher level code can retry
174 * the whole (combined) message and *NOT* issue STOP.
175 */
176 scllo(adap);
177 }
178 sdahi(adap);
179 if (sclhi(adap) < 0) { /* timeout */
180 bit_dbg(1, &i2c_adap->dev,
181 "i2c_outb: 0x%02x, timeout at ack\n", (int)c);
182 return -ETIMEDOUT;
183 }
184
185 /* read ack: SDA should be pulled down by slave, or it may
186 * NAK (usually to report problems with the data we wrote).
187 */
188 ack = !getsda(adap); /* ack: sda is pulled low -> success */
189 bit_dbg(2, &i2c_adap->dev, "i2c_outb: 0x%02x %s\n", (int)c,
190 ack ? "A" : "NA");
191
192 scllo(adap);
193 return ack;
194 /* assert: scl is low (sda undef) */
195}
196
197
198static int i2c_inb(struct i2c_adapter *i2c_adap)
199{
200 /* read byte via i2c port, without start/stop sequence */
201 /* acknowledge is sent in i2c_read. */
202 int i;
203 unsigned char indata = 0;
204 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
205
206 /* assert: scl is low */
207 sdahi(adap);
208 for (i = 0; i < 8; i++) {
209 if (sclhi(adap) < 0) { /* timeout */
210 bit_dbg(1, &i2c_adap->dev,
211 "i2c_inb: timeout at bit #%d\n",
212 7 - i);
213 return -ETIMEDOUT;
214 }
215 indata *= 2;
216 if (getsda(adap))
217 indata |= 0x01;
218 setscl(adap, 0);
219 udelay(i == 7 ? adap->udelay / 2 : adap->udelay);
220 }
221 /* assert: scl is low */
222 return indata;
223}
224
225/*
226 * Sanity check for the adapter hardware - check the reaction of
227 * the bus lines only if it seems to be idle.
228 */
229static int test_bus(struct i2c_adapter *i2c_adap)
230{
231 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
232 const char *name = i2c_adap->name;
233 int scl, sda, ret;
234
235 if (adap->pre_xfer) {
236 ret = adap->pre_xfer(i2c_adap);
237 if (ret < 0)
238 return -ENODEV;
239 }
240
241 if (adap->getscl == NULL)
242 pr_info("%s: Testing SDA only, SCL is not readable\n", name);
243
244 sda = getsda(adap);
245 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
246 if (!scl || !sda) {
247 printk(KERN_WARNING
248 "%s: bus seems to be busy (scl=%d, sda=%d)\n",
249 name, scl, sda);
250 goto bailout;
251 }
252
253 sdalo(adap);
254 sda = getsda(adap);
255 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
256 if (sda) {
257 printk(KERN_WARNING "%s: SDA stuck high!\n", name);
258 goto bailout;
259 }
260 if (!scl) {
261 printk(KERN_WARNING
262 "%s: SCL unexpected low while pulling SDA low!\n",
263 name);
264 goto bailout;
265 }
266
267 sdahi(adap);
268 sda = getsda(adap);
269 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
270 if (!sda) {
271 printk(KERN_WARNING "%s: SDA stuck low!\n", name);
272 goto bailout;
273 }
274 if (!scl) {
275 printk(KERN_WARNING
276 "%s: SCL unexpected low while pulling SDA high!\n",
277 name);
278 goto bailout;
279 }
280
281 scllo(adap);
282 sda = getsda(adap);
283 scl = (adap->getscl == NULL) ? 0 : getscl(adap);
284 if (scl) {
285 printk(KERN_WARNING "%s: SCL stuck high!\n", name);
286 goto bailout;
287 }
288 if (!sda) {
289 printk(KERN_WARNING
290 "%s: SDA unexpected low while pulling SCL low!\n",
291 name);
292 goto bailout;
293 }
294
295 sclhi(adap);
296 sda = getsda(adap);
297 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
298 if (!scl) {
299 printk(KERN_WARNING "%s: SCL stuck low!\n", name);
300 goto bailout;
301 }
302 if (!sda) {
303 printk(KERN_WARNING
304 "%s: SDA unexpected low while pulling SCL high!\n",
305 name);
306 goto bailout;
307 }
308
309 if (adap->post_xfer)
310 adap->post_xfer(i2c_adap);
311
312 pr_info("%s: Test OK\n", name);
313 return 0;
314bailout:
315 sdahi(adap);
316 sclhi(adap);
317
318 if (adap->post_xfer)
319 adap->post_xfer(i2c_adap);
320
321 return -ENODEV;
322}
323
324/* ----- Utility functions
325 */
326
327/* try_address tries to contact a chip for a number of
328 * times before it gives up.
329 * return values:
330 * 1 chip answered
331 * 0 chip did not answer
332 * -x transmission error
333 */
334static int try_address(struct i2c_adapter *i2c_adap,
335 unsigned char addr, int retries)
336{
337 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
338 int i, ret = 0;
339
340 for (i = 0; i <= retries; i++) {
341 ret = i2c_outb(i2c_adap, addr);
342 if (ret == 1 || i == retries)
343 break;
344 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
345 i2c_stop(adap);
346 udelay(adap->udelay);
347 yield();
348 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
349 i2c_start(adap);
350 }
351 if (i && ret)
352 bit_dbg(1, &i2c_adap->dev,
353 "Used %d tries to %s client at 0x%02x: %s\n", i + 1,
354 addr & 1 ? "read from" : "write to", addr >> 1,
355 ret == 1 ? "success" : "failed, timeout?");
356 return ret;
357}
358
359static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
360{
361 const unsigned char *temp = msg->buf;
362 int count = msg->len;
363 unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
364 int retval;
365 int wrcount = 0;
366
367 while (count > 0) {
368 retval = i2c_outb(i2c_adap, *temp);
369
370 /* OK/ACK; or ignored NAK */
371 if ((retval > 0) || (nak_ok && (retval == 0))) {
372 count--;
373 temp++;
374 wrcount++;
375
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.
379 */
380 } else if (retval == 0) {
381 dev_err(&i2c_adap->dev, "sendbytes: NAK bailout.\n");
382 return -EIO;
383
384 /* Timeout; or (someday) lost arbitration
385 *
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.
390 */
391 } else {
392 dev_err(&i2c_adap->dev, "sendbytes: error %d\n",
393 retval);
394 return retval;
395 }
396 }
397 return wrcount;
398}
399
400static int acknak(struct i2c_adapter *i2c_adap, int is_ack)
401{
402 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
403
404 /* assert: sda is high */
405 if (is_ack) /* send ack */
406 setsda(adap, 0);
407 udelay((adap->udelay + 1) / 2);
408 if (sclhi(adap) < 0) { /* timeout */
409 dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n");
410 return -ETIMEDOUT;
411 }
412 scllo(adap);
413 return 0;
414}
415
416static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
417{
418 int inval;
419 int rdcount = 0; /* counts bytes read */
420 unsigned char *temp = msg->buf;
421 int count = msg->len;
422 const unsigned flags = msg->flags;
423
424 while (count > 0) {
425 inval = i2c_inb(i2c_adap);
426 if (inval >= 0) {
427 *temp = inval;
428 rdcount++;
429 } else { /* read timed out */
430 break;
431 }
432
433 temp++;
434 count--;
435
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))
441 acknak(i2c_adap, 0);
442 dev_err(&i2c_adap->dev,
443 "readbytes: invalid block length (%d)\n",
444 inval);
445 return -EPROTO;
446 }
447 /* The original count value accounts for the extra
448 bytes, that is, either 1 for a regular transaction,
449 or 2 for a PEC transaction. */
450 count += inval;
451 msg->len += inval;
452 }
453
454 bit_dbg(2, &i2c_adap->dev, "readbytes: 0x%02x %s\n",
455 inval,
456 (flags & I2C_M_NO_RD_ACK)
457 ? "(no ack/nak)"
458 : (count ? "A" : "NA"));
459
460 if (!(flags & I2C_M_NO_RD_ACK)) {
461 inval = acknak(i2c_adap, count);
462 if (inval < 0)
463 return inval;
464 }
465 }
466 return rdcount;
467}
468
469/* doAddress initiates the transfer by generating the start condition (in
470 * try_address) and transmits the address in the necessary format to handle
471 * reads, writes as well as 10bit-addresses.
472 * returns:
473 * 0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set
474 * -x an error occurred (like: -ENXIO if the device did not answer, or
475 * -ETIMEDOUT, for example if the lines are stuck...)
476 */
477static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
478{
479 unsigned short flags = msg->flags;
480 unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
481 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
482
483 unsigned char addr;
484 int ret, retries;
485
486 retries = nak_ok ? 0 : i2c_adap->retries;
487
488 if (flags & I2C_M_TEN) {
489 /* a ten bit address */
490 addr = 0xf0 | ((msg->addr >> 7) & 0x06);
491 bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr);
492 /* try extended address code...*/
493 ret = try_address(i2c_adap, addr, retries);
494 if ((ret != 1) && !nak_ok) {
495 dev_err(&i2c_adap->dev,
496 "died at extended address code\n");
497 return -ENXIO;
498 }
499 /* the remaining 8 bit address */
500 ret = i2c_outb(i2c_adap, msg->addr & 0xff);
501 if ((ret != 1) && !nak_ok) {
502 /* the chip did not ack / xmission error occurred */
503 dev_err(&i2c_adap->dev, "died at 2nd address code\n");
504 return -ENXIO;
505 }
506 if (flags & I2C_M_RD) {
507 bit_dbg(3, &i2c_adap->dev,
508 "emitting repeated start condition\n");
509 i2c_repstart(adap);
510 /* okay, now switch into reading mode */
511 addr |= 0x01;
512 ret = try_address(i2c_adap, addr, retries);
513 if ((ret != 1) && !nak_ok) {
514 dev_err(&i2c_adap->dev,
515 "died at repeated address code\n");
516 return -EIO;
517 }
518 }
519 } else { /* normal 7bit address */
520 addr = i2c_8bit_addr_from_msg(msg);
521 if (flags & I2C_M_REV_DIR_ADDR)
522 addr ^= 1;
523 ret = try_address(i2c_adap, addr, retries);
524 if ((ret != 1) && !nak_ok)
525 return -ENXIO;
526 }
527
528 return 0;
529}
530
531static int bit_xfer(struct i2c_adapter *i2c_adap,
532 struct i2c_msg msgs[], int num)
533{
534 struct i2c_msg *pmsg;
535 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
536 int i, ret;
537 unsigned short nak_ok;
538
539 if (adap->pre_xfer) {
540 ret = adap->pre_xfer(i2c_adap);
541 if (ret < 0)
542 return ret;
543 }
544
545 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
546 i2c_start(adap);
547 for (i = 0; i < num; i++) {
548 pmsg = &msgs[i];
549 nak_ok = pmsg->flags & I2C_M_IGNORE_NAK;
550 if (!(pmsg->flags & I2C_M_NOSTART)) {
551 if (i) {
552 if (msgs[i - 1].flags & I2C_M_STOP) {
553 bit_dbg(3, &i2c_adap->dev,
554 "emitting enforced stop/start condition\n");
555 i2c_stop(adap);
556 i2c_start(adap);
557 } else {
558 bit_dbg(3, &i2c_adap->dev,
559 "emitting repeated start condition\n");
560 i2c_repstart(adap);
561 }
562 }
563 ret = bit_doAddress(i2c_adap, pmsg);
564 if ((ret != 0) && !nak_ok) {
565 bit_dbg(1, &i2c_adap->dev,
566 "NAK from device addr 0x%02x msg #%d\n",
567 msgs[i].addr, i);
568 goto bailout;
569 }
570 }
571 if (pmsg->flags & I2C_M_RD) {
572 /* read bytes into buffer*/
573 ret = readbytes(i2c_adap, pmsg);
574 if (ret >= 1)
575 bit_dbg(2, &i2c_adap->dev, "read %d byte%s\n",
576 ret, ret == 1 ? "" : "s");
577 if (ret < pmsg->len) {
578 if (ret >= 0)
579 ret = -EIO;
580 goto bailout;
581 }
582 } else {
583 /* write bytes from buffer */
584 ret = sendbytes(i2c_adap, pmsg);
585 if (ret >= 1)
586 bit_dbg(2, &i2c_adap->dev, "wrote %d byte%s\n",
587 ret, ret == 1 ? "" : "s");
588 if (ret < pmsg->len) {
589 if (ret >= 0)
590 ret = -EIO;
591 goto bailout;
592 }
593 }
594 }
595 ret = i;
596
597bailout:
598 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
599 i2c_stop(adap);
600
601 if (adap->post_xfer)
602 adap->post_xfer(i2c_adap);
603 return ret;
604}
605
606/*
607 * We print a warning when we are not flagged to support atomic transfers but
608 * will try anyhow. That's what the I2C core would do as well. Sadly, we can't
609 * modify the algorithm struct at probe time because this struct is exported
610 * 'const'.
611 */
612static int bit_xfer_atomic(struct i2c_adapter *i2c_adap, struct i2c_msg msgs[],
613 int num)
614{
615 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
616
617 if (!adap->can_do_atomic)
618 dev_warn(&i2c_adap->dev, "not flagged for atomic transfers\n");
619
620 return bit_xfer(i2c_adap, msgs, num);
621}
622
623static u32 bit_func(struct i2c_adapter *adap)
624{
625 return I2C_FUNC_I2C | I2C_FUNC_NOSTART | I2C_FUNC_SMBUS_EMUL |
626 I2C_FUNC_SMBUS_READ_BLOCK_DATA |
627 I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
628 I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
629}
630
631
632/* -----exported algorithm data: ------------------------------------- */
633
634const struct i2c_algorithm i2c_bit_algo = {
635 .master_xfer = bit_xfer,
636 .master_xfer_atomic = bit_xfer_atomic,
637 .functionality = bit_func,
638};
639EXPORT_SYMBOL(i2c_bit_algo);
640
641static const struct i2c_adapter_quirks i2c_bit_quirk_no_clk_stretch = {
642 .flags = I2C_AQ_NO_CLK_STRETCH,
643};
644
645/*
646 * registering functions to load algorithms at runtime
647 */
648static int __i2c_bit_add_bus(struct i2c_adapter *adap,
649 int (*add_adapter)(struct i2c_adapter *))
650{
651 struct i2c_algo_bit_data *bit_adap = adap->algo_data;
652 int ret;
653
654 if (bit_test) {
655 ret = test_bus(adap);
656 if (bit_test >= 2 && ret < 0)
657 return -ENODEV;
658 }
659
660 /* register new adapter to i2c module... */
661 adap->algo = &i2c_bit_algo;
662 adap->retries = 3;
663 if (bit_adap->getscl == NULL)
664 adap->quirks = &i2c_bit_quirk_no_clk_stretch;
665
666 /*
667 * We tried forcing SCL/SDA to an initial state here. But that caused a
668 * regression, sadly. Check Bugzilla #200045 for details.
669 */
670
671 ret = add_adapter(adap);
672 if (ret < 0)
673 return ret;
674
675 /* Complain if SCL can't be read */
676 if (bit_adap->getscl == NULL) {
677 dev_warn(&adap->dev, "Not I2C compliant: can't read SCL\n");
678 dev_warn(&adap->dev, "Bus may be unreliable\n");
679 }
680 return 0;
681}
682
683int i2c_bit_add_bus(struct i2c_adapter *adap)
684{
685 return __i2c_bit_add_bus(adap, i2c_add_adapter);
686}
687EXPORT_SYMBOL(i2c_bit_add_bus);
688
689int i2c_bit_add_numbered_bus(struct i2c_adapter *adap)
690{
691 return __i2c_bit_add_bus(adap, i2c_add_numbered_adapter);
692}
693EXPORT_SYMBOL(i2c_bit_add_numbered_bus);
694
695MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
696MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm");
697MODULE_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
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
620static const 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");