Loading...
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., 675 Mass Ave, Cambridge, MA 02139, USA.
19 * ------------------------------------------------------------------------- */
20
21/* With some changes from Frodo Looijaard <frodol@dds.nl>, Kyösti Mälkki
22 <kmalkki@cc.hut.fi> and Jean Delvare <khali@linux-fr.org> */
23
24#include <linux/kernel.h>
25#include <linux/module.h>
26#include <linux/delay.h>
27#include <linux/init.h>
28#include <linux/errno.h>
29#include <linux/sched.h>
30#include <linux/i2c.h>
31#include <linux/i2c-algo-bit.h>
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, bool, 0);
51MODULE_PARM_DESC(bit_test, "Test the lines of the bus to see if it is 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 return -ETIMEDOUT;
108 cond_resched();
109 }
110#ifdef DEBUG
111 if (jiffies != start && i2c_debug >= 3)
112 pr_debug("i2c-algo-bit: needed %ld jiffies for SCL to go "
113 "high\n", jiffies - start);
114#endif
115
116done:
117 udelay(adap->udelay);
118 return 0;
119}
120
121
122/* --- other auxiliary functions -------------------------------------- */
123static void i2c_start(struct i2c_algo_bit_data *adap)
124{
125 /* assert: scl, sda are high */
126 setsda(adap, 0);
127 udelay(adap->udelay);
128 scllo(adap);
129}
130
131static void i2c_repstart(struct i2c_algo_bit_data *adap)
132{
133 /* assert: scl is low */
134 sdahi(adap);
135 sclhi(adap);
136 setsda(adap, 0);
137 udelay(adap->udelay);
138 scllo(adap);
139}
140
141
142static void i2c_stop(struct i2c_algo_bit_data *adap)
143{
144 /* assert: scl is low */
145 sdalo(adap);
146 sclhi(adap);
147 setsda(adap, 1);
148 udelay(adap->udelay);
149}
150
151
152
153/* send a byte without start cond., look for arbitration,
154 check ackn. from slave */
155/* returns:
156 * 1 if the device acknowledged
157 * 0 if the device did not ack
158 * -ETIMEDOUT if an error occurred (while raising the scl line)
159 */
160static int i2c_outb(struct i2c_adapter *i2c_adap, unsigned char c)
161{
162 int i;
163 int sb;
164 int ack;
165 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
166
167 /* assert: scl is low */
168 for (i = 7; i >= 0; i--) {
169 sb = (c >> i) & 1;
170 setsda(adap, sb);
171 udelay((adap->udelay + 1) / 2);
172 if (sclhi(adap) < 0) { /* timed out */
173 bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
174 "timeout at bit #%d\n", (int)c, i);
175 return -ETIMEDOUT;
176 }
177 /* FIXME do arbitration here:
178 * if (sb && !getsda(adap)) -> ouch! Get out of here.
179 *
180 * Report a unique code, so higher level code can retry
181 * the whole (combined) message and *NOT* issue STOP.
182 */
183 scllo(adap);
184 }
185 sdahi(adap);
186 if (sclhi(adap) < 0) { /* timeout */
187 bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
188 "timeout at ack\n", (int)c);
189 return -ETIMEDOUT;
190 }
191
192 /* read ack: SDA should be pulled down by slave, or it may
193 * NAK (usually to report problems with the data we wrote).
194 */
195 ack = !getsda(adap); /* ack: sda is pulled low -> success */
196 bit_dbg(2, &i2c_adap->dev, "i2c_outb: 0x%02x %s\n", (int)c,
197 ack ? "A" : "NA");
198
199 scllo(adap);
200 return ack;
201 /* assert: scl is low (sda undef) */
202}
203
204
205static int i2c_inb(struct i2c_adapter *i2c_adap)
206{
207 /* read byte via i2c port, without start/stop sequence */
208 /* acknowledge is sent in i2c_read. */
209 int i;
210 unsigned char indata = 0;
211 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
212
213 /* assert: scl is low */
214 sdahi(adap);
215 for (i = 0; i < 8; i++) {
216 if (sclhi(adap) < 0) { /* timeout */
217 bit_dbg(1, &i2c_adap->dev, "i2c_inb: timeout at bit "
218 "#%d\n", 7 - i);
219 return -ETIMEDOUT;
220 }
221 indata *= 2;
222 if (getsda(adap))
223 indata |= 0x01;
224 setscl(adap, 0);
225 udelay(i == 7 ? adap->udelay / 2 : adap->udelay);
226 }
227 /* assert: scl is low */
228 return indata;
229}
230
231/*
232 * Sanity check for the adapter hardware - check the reaction of
233 * the bus lines only if it seems to be idle.
234 */
235static int test_bus(struct i2c_adapter *i2c_adap)
236{
237 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
238 const char *name = i2c_adap->name;
239 int scl, sda, ret;
240
241 if (adap->pre_xfer) {
242 ret = adap->pre_xfer(i2c_adap);
243 if (ret < 0)
244 return -ENODEV;
245 }
246
247 if (adap->getscl == NULL)
248 pr_info("%s: Testing SDA only, SCL is not readable\n", name);
249
250 sda = getsda(adap);
251 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
252 if (!scl || !sda) {
253 printk(KERN_WARNING "%s: bus seems to be busy\n", name);
254 goto bailout;
255 }
256
257 sdalo(adap);
258 sda = getsda(adap);
259 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
260 if (sda) {
261 printk(KERN_WARNING "%s: SDA stuck high!\n", name);
262 goto bailout;
263 }
264 if (!scl) {
265 printk(KERN_WARNING "%s: SCL unexpected low "
266 "while pulling SDA low!\n", name);
267 goto bailout;
268 }
269
270 sdahi(adap);
271 sda = getsda(adap);
272 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
273 if (!sda) {
274 printk(KERN_WARNING "%s: SDA stuck low!\n", name);
275 goto bailout;
276 }
277 if (!scl) {
278 printk(KERN_WARNING "%s: SCL unexpected low "
279 "while pulling SDA high!\n", name);
280 goto bailout;
281 }
282
283 scllo(adap);
284 sda = getsda(adap);
285 scl = (adap->getscl == NULL) ? 0 : getscl(adap);
286 if (scl) {
287 printk(KERN_WARNING "%s: SCL stuck high!\n", name);
288 goto bailout;
289 }
290 if (!sda) {
291 printk(KERN_WARNING "%s: SDA unexpected low "
292 "while pulling SCL low!\n", name);
293 goto bailout;
294 }
295
296 sclhi(adap);
297 sda = getsda(adap);
298 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
299 if (!scl) {
300 printk(KERN_WARNING "%s: SCL stuck low!\n", name);
301 goto bailout;
302 }
303 if (!sda) {
304 printk(KERN_WARNING "%s: SDA unexpected low "
305 "while pulling SCL high!\n", 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, "Used %d tries to %s client at "
353 "0x%02x: %s\n", i + 1,
354 addr & 1 ? "read from" : "write to", addr >> 1,
355 ret == 1 ? "success" : "failed, timeout?");
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, "readbytes: invalid "
443 "block length (%d)\n", inval);
444 return -EREMOTEIO;
445 }
446 /* The original count value accounts for the extra
447 bytes, that is, either 1 for a regular transaction,
448 or 2 for a PEC transaction. */
449 count += inval;
450 msg->len += inval;
451 }
452
453 bit_dbg(2, &i2c_adap->dev, "readbytes: 0x%02x %s\n",
454 inval,
455 (flags & I2C_M_NO_RD_ACK)
456 ? "(no ack/nak)"
457 : (count ? "A" : "NA"));
458
459 if (!(flags & I2C_M_NO_RD_ACK)) {
460 inval = acknak(i2c_adap, count);
461 if (inval < 0)
462 return inval;
463 }
464 }
465 return rdcount;
466}
467
468/* doAddress initiates the transfer by generating the start condition (in
469 * try_address) and transmits the address in the necessary format to handle
470 * reads, writes as well as 10bit-addresses.
471 * returns:
472 * 0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set
473 * -x an error occurred (like: -EREMOTEIO if the device did not answer, or
474 * -ETIMEDOUT, for example if the lines are stuck...)
475 */
476static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
477{
478 unsigned short flags = msg->flags;
479 unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
480 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
481
482 unsigned char addr;
483 int ret, retries;
484
485 retries = nak_ok ? 0 : i2c_adap->retries;
486
487 if (flags & I2C_M_TEN) {
488 /* a ten bit address */
489 addr = 0xf0 | ((msg->addr >> 7) & 0x03);
490 bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr);
491 /* try extended address code...*/
492 ret = try_address(i2c_adap, addr, retries);
493 if ((ret != 1) && !nak_ok) {
494 dev_err(&i2c_adap->dev,
495 "died at extended address code\n");
496 return -EREMOTEIO;
497 }
498 /* the remaining 8 bit address */
499 ret = i2c_outb(i2c_adap, msg->addr & 0x7f);
500 if ((ret != 1) && !nak_ok) {
501 /* the chip did not ack / xmission error occurred */
502 dev_err(&i2c_adap->dev, "died at 2nd address code\n");
503 return -EREMOTEIO;
504 }
505 if (flags & I2C_M_RD) {
506 bit_dbg(3, &i2c_adap->dev, "emitting repeated "
507 "start condition\n");
508 i2c_repstart(adap);
509 /* okay, now switch into reading mode */
510 addr |= 0x01;
511 ret = try_address(i2c_adap, addr, retries);
512 if ((ret != 1) && !nak_ok) {
513 dev_err(&i2c_adap->dev,
514 "died at repeated address code\n");
515 return -EREMOTEIO;
516 }
517 }
518 } else { /* normal 7bit address */
519 addr = msg->addr << 1;
520 if (flags & I2C_M_RD)
521 addr |= 1;
522 if (flags & I2C_M_REV_DIR_ADDR)
523 addr ^= 1;
524 ret = try_address(i2c_adap, addr, retries);
525 if ((ret != 1) && !nak_ok)
526 return -ENXIO;
527 }
528
529 return 0;
530}
531
532static int bit_xfer(struct i2c_adapter *i2c_adap,
533 struct i2c_msg msgs[], int num)
534{
535 struct i2c_msg *pmsg;
536 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
537 int i, ret;
538 unsigned short nak_ok;
539
540 if (adap->pre_xfer) {
541 ret = adap->pre_xfer(i2c_adap);
542 if (ret < 0)
543 return ret;
544 }
545
546 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
547 i2c_start(adap);
548 for (i = 0; i < num; i++) {
549 pmsg = &msgs[i];
550 nak_ok = pmsg->flags & I2C_M_IGNORE_NAK;
551 if (!(pmsg->flags & I2C_M_NOSTART)) {
552 if (i) {
553 bit_dbg(3, &i2c_adap->dev, "emitting "
554 "repeated start condition\n");
555 i2c_repstart(adap);
556 }
557 ret = bit_doAddress(i2c_adap, pmsg);
558 if ((ret != 0) && !nak_ok) {
559 bit_dbg(1, &i2c_adap->dev, "NAK from "
560 "device addr 0x%02x msg #%d\n",
561 msgs[i].addr, i);
562 goto bailout;
563 }
564 }
565 if (pmsg->flags & I2C_M_RD) {
566 /* read bytes into buffer*/
567 ret = readbytes(i2c_adap, pmsg);
568 if (ret >= 1)
569 bit_dbg(2, &i2c_adap->dev, "read %d byte%s\n",
570 ret, ret == 1 ? "" : "s");
571 if (ret < pmsg->len) {
572 if (ret >= 0)
573 ret = -EREMOTEIO;
574 goto bailout;
575 }
576 } else {
577 /* write bytes from buffer */
578 ret = sendbytes(i2c_adap, pmsg);
579 if (ret >= 1)
580 bit_dbg(2, &i2c_adap->dev, "wrote %d byte%s\n",
581 ret, ret == 1 ? "" : "s");
582 if (ret < pmsg->len) {
583 if (ret >= 0)
584 ret = -EREMOTEIO;
585 goto bailout;
586 }
587 }
588 }
589 ret = i;
590
591bailout:
592 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
593 i2c_stop(adap);
594
595 if (adap->post_xfer)
596 adap->post_xfer(i2c_adap);
597 return ret;
598}
599
600static u32 bit_func(struct i2c_adapter *adap)
601{
602 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
603 I2C_FUNC_SMBUS_READ_BLOCK_DATA |
604 I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
605 I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
606}
607
608
609/* -----exported algorithm data: ------------------------------------- */
610
611static const struct i2c_algorithm i2c_bit_algo = {
612 .master_xfer = bit_xfer,
613 .functionality = bit_func,
614};
615
616/*
617 * registering functions to load algorithms at runtime
618 */
619static int __i2c_bit_add_bus(struct i2c_adapter *adap,
620 int (*add_adapter)(struct i2c_adapter *))
621{
622 struct i2c_algo_bit_data *bit_adap = adap->algo_data;
623 int ret;
624
625 if (bit_test) {
626 ret = test_bus(adap);
627 if (ret < 0)
628 return -ENODEV;
629 }
630
631 /* register new adapter to i2c module... */
632 adap->algo = &i2c_bit_algo;
633 adap->retries = 3;
634
635 ret = add_adapter(adap);
636 if (ret < 0)
637 return ret;
638
639 /* Complain if SCL can't be read */
640 if (bit_adap->getscl == NULL) {
641 dev_warn(&adap->dev, "Not I2C compliant: can't read SCL\n");
642 dev_warn(&adap->dev, "Bus may be unreliable\n");
643 }
644 return 0;
645}
646
647int i2c_bit_add_bus(struct i2c_adapter *adap)
648{
649 return __i2c_bit_add_bus(adap, i2c_add_adapter);
650}
651EXPORT_SYMBOL(i2c_bit_add_bus);
652
653int i2c_bit_add_numbered_bus(struct i2c_adapter *adap)
654{
655 return __i2c_bit_add_bus(adap, i2c_add_numbered_adapter);
656}
657EXPORT_SYMBOL(i2c_bit_add_numbered_bus);
658
659MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
660MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm");
661MODULE_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");