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/slab.h>
28 #include <linux/init.h>
29 #include <linux/errno.h>
30 #include <linux/sched.h>
31 #include <linux/i2c.h>
32 #include <linux/i2c-algo-bit.h>
33
34
35 /* ----- global defines ----------------------------------------------- */
36
37 #ifdef DEBUG
38 #define bit_dbg(level, dev, format, args...) \
39 do { \
40 if (i2c_debug >= level) \
41 dev_dbg(dev, format, ##args); \
42 } while (0)
43 #else
44 #define bit_dbg(level, dev, format, args...) \
45 do {} while (0)
46 #endif /* DEBUG */
47
48 /* ----- global variables --------------------------------------------- */
49
50 static int bit_test; /* see if the line-setting functions work */
51 module_param(bit_test, bool, 0);
52 MODULE_PARM_DESC(bit_test, "Test the lines of the bus to see if it is stuck");
53
54 #ifdef DEBUG
55 static int i2c_debug = 1;
56 module_param(i2c_debug, int, S_IRUGO | S_IWUSR);
57 MODULE_PARM_DESC(i2c_debug,
58 "debug level - 0 off; 1 normal; 2 verbose; 3 very verbose");
59 #endif
60
61 /* --- setting states on the bus with the right timing: --------------- */
62
63 #define setsda(adap, val) adap->setsda(adap->data, val)
64 #define setscl(adap, val) adap->setscl(adap->data, val)
65 #define getsda(adap) adap->getsda(adap->data)
66 #define getscl(adap) adap->getscl(adap->data)
67
sdalo(struct i2c_algo_bit_data * adap)68 static inline void sdalo(struct i2c_algo_bit_data *adap)
69 {
70 setsda(adap, 0);
71 udelay((adap->udelay + 1) / 2);
72 }
73
sdahi(struct i2c_algo_bit_data * adap)74 static inline void sdahi(struct i2c_algo_bit_data *adap)
75 {
76 setsda(adap, 1);
77 udelay((adap->udelay + 1) / 2);
78 }
79
scllo(struct i2c_algo_bit_data * adap)80 static inline void scllo(struct i2c_algo_bit_data *adap)
81 {
82 setscl(adap, 0);
83 udelay(adap->udelay / 2);
84 }
85
86 /*
87 * Raise scl line, and do checking for delays. This is necessary for slower
88 * devices.
89 */
sclhi(struct i2c_algo_bit_data * adap)90 static int sclhi(struct i2c_algo_bit_data *adap)
91 {
92 unsigned long start;
93
94 setscl(adap, 1);
95
96 /* Not all adapters have scl sense line... */
97 if (!adap->getscl)
98 goto done;
99
100 start = jiffies;
101 while (!getscl(adap)) {
102 /* This hw knows how to read the clock line, so we wait
103 * until it actually gets high. This is safer as some
104 * chips may hold it low ("clock stretching") while they
105 * are processing data internally.
106 */
107 if (time_after_eq(jiffies, start + adap->timeout))
108 return -ETIMEDOUT;
109 cond_resched();
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
117 done:
118 udelay(adap->udelay);
119 return 0;
120 }
121
122
123 /* --- other auxiliary functions -------------------------------------- */
i2c_start(struct i2c_algo_bit_data * adap)124 static 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
i2c_repstart(struct i2c_algo_bit_data * adap)132 static 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
i2c_stop(struct i2c_algo_bit_data * adap)143 static 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 */
i2c_outb(struct i2c_adapter * i2c_adap,unsigned char c)161 static 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
i2c_inb(struct i2c_adapter * i2c_adap)206 static 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 */
test_bus(struct i2c_algo_bit_data * adap,char * name)236 static int test_bus(struct i2c_algo_bit_data *adap, char *name)
237 {
238 int scl, sda;
239
240 if (adap->getscl == NULL)
241 pr_info("%s: Testing SDA only, SCL is not readable\n", name);
242
243 sda = getsda(adap);
244 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
245 if (!scl || !sda) {
246 printk(KERN_WARNING "%s: bus seems to be busy\n", name);
247 goto bailout;
248 }
249
250 sdalo(adap);
251 sda = getsda(adap);
252 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
253 if (sda) {
254 printk(KERN_WARNING "%s: SDA stuck high!\n", name);
255 goto bailout;
256 }
257 if (!scl) {
258 printk(KERN_WARNING "%s: SCL unexpected low "
259 "while pulling SDA low!\n", name);
260 goto bailout;
261 }
262
263 sdahi(adap);
264 sda = getsda(adap);
265 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
266 if (!sda) {
267 printk(KERN_WARNING "%s: SDA stuck low!\n", name);
268 goto bailout;
269 }
270 if (!scl) {
271 printk(KERN_WARNING "%s: SCL unexpected low "
272 "while pulling SDA high!\n", name);
273 goto bailout;
274 }
275
276 scllo(adap);
277 sda = getsda(adap);
278 scl = (adap->getscl == NULL) ? 0 : getscl(adap);
279 if (scl) {
280 printk(KERN_WARNING "%s: SCL stuck high!\n", name);
281 goto bailout;
282 }
283 if (!sda) {
284 printk(KERN_WARNING "%s: SDA unexpected low "
285 "while pulling SCL low!\n", name);
286 goto bailout;
287 }
288
289 sclhi(adap);
290 sda = getsda(adap);
291 scl = (adap->getscl == NULL) ? 1 : getscl(adap);
292 if (!scl) {
293 printk(KERN_WARNING "%s: SCL stuck low!\n", name);
294 goto bailout;
295 }
296 if (!sda) {
297 printk(KERN_WARNING "%s: SDA unexpected low "
298 "while pulling SCL high!\n", name);
299 goto bailout;
300 }
301 pr_info("%s: Test OK\n", name);
302 return 0;
303 bailout:
304 sdahi(adap);
305 sclhi(adap);
306 return -ENODEV;
307 }
308
309 /* ----- Utility functions
310 */
311
312 /* try_address tries to contact a chip for a number of
313 * times before it gives up.
314 * return values:
315 * 1 chip answered
316 * 0 chip did not answer
317 * -x transmission error
318 */
try_address(struct i2c_adapter * i2c_adap,unsigned char addr,int retries)319 static int try_address(struct i2c_adapter *i2c_adap,
320 unsigned char addr, int retries)
321 {
322 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
323 int i, ret = 0;
324
325 for (i = 0; i <= retries; i++) {
326 ret = i2c_outb(i2c_adap, addr);
327 if (ret == 1 || i == retries)
328 break;
329 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
330 i2c_stop(adap);
331 udelay(adap->udelay);
332 yield();
333 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
334 i2c_start(adap);
335 }
336 if (i && ret)
337 bit_dbg(1, &i2c_adap->dev, "Used %d tries to %s client at "
338 "0x%02x: %s\n", i + 1,
339 addr & 1 ? "read from" : "write to", addr >> 1,
340 ret == 1 ? "success" : "failed, timeout?");
341 return ret;
342 }
343
sendbytes(struct i2c_adapter * i2c_adap,struct i2c_msg * msg)344 static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
345 {
346 const unsigned char *temp = msg->buf;
347 int count = msg->len;
348 unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
349 int retval;
350 int wrcount = 0;
351
352 while (count > 0) {
353 retval = i2c_outb(i2c_adap, *temp);
354
355 /* OK/ACK; or ignored NAK */
356 if ((retval > 0) || (nak_ok && (retval == 0))) {
357 count--;
358 temp++;
359 wrcount++;
360
361 /* A slave NAKing the master means the slave didn't like
362 * something about the data it saw. For example, maybe
363 * the SMBus PEC was wrong.
364 */
365 } else if (retval == 0) {
366 dev_err(&i2c_adap->dev, "sendbytes: NAK bailout.\n");
367 return -EIO;
368
369 /* Timeout; or (someday) lost arbitration
370 *
371 * FIXME Lost ARB implies retrying the transaction from
372 * the first message, after the "winning" master issues
373 * its STOP. As a rule, upper layer code has no reason
374 * to know or care about this ... it is *NOT* an error.
375 */
376 } else {
377 dev_err(&i2c_adap->dev, "sendbytes: error %d\n",
378 retval);
379 return retval;
380 }
381 }
382 return wrcount;
383 }
384
acknak(struct i2c_adapter * i2c_adap,int is_ack)385 static int acknak(struct i2c_adapter *i2c_adap, int is_ack)
386 {
387 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
388
389 /* assert: sda is high */
390 if (is_ack) /* send ack */
391 setsda(adap, 0);
392 udelay((adap->udelay + 1) / 2);
393 if (sclhi(adap) < 0) { /* timeout */
394 dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n");
395 return -ETIMEDOUT;
396 }
397 scllo(adap);
398 return 0;
399 }
400
readbytes(struct i2c_adapter * i2c_adap,struct i2c_msg * msg)401 static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
402 {
403 int inval;
404 int rdcount = 0; /* counts bytes read */
405 unsigned char *temp = msg->buf;
406 int count = msg->len;
407 const unsigned flags = msg->flags;
408
409 while (count > 0) {
410 inval = i2c_inb(i2c_adap);
411 if (inval >= 0) {
412 *temp = inval;
413 rdcount++;
414 } else { /* read timed out */
415 break;
416 }
417
418 temp++;
419 count--;
420
421 /* Some SMBus transactions require that we receive the
422 transaction length as the first read byte. */
423 if (rdcount == 1 && (flags & I2C_M_RECV_LEN)) {
424 if (inval <= 0 || inval > I2C_SMBUS_BLOCK_MAX) {
425 if (!(flags & I2C_M_NO_RD_ACK))
426 acknak(i2c_adap, 0);
427 dev_err(&i2c_adap->dev, "readbytes: invalid "
428 "block length (%d)\n", inval);
429 return -EREMOTEIO;
430 }
431 /* The original count value accounts for the extra
432 bytes, that is, either 1 for a regular transaction,
433 or 2 for a PEC transaction. */
434 count += inval;
435 msg->len += inval;
436 }
437
438 bit_dbg(2, &i2c_adap->dev, "readbytes: 0x%02x %s\n",
439 inval,
440 (flags & I2C_M_NO_RD_ACK)
441 ? "(no ack/nak)"
442 : (count ? "A" : "NA"));
443
444 if (!(flags & I2C_M_NO_RD_ACK)) {
445 inval = acknak(i2c_adap, count);
446 if (inval < 0)
447 return inval;
448 }
449 }
450 return rdcount;
451 }
452
453 /* doAddress initiates the transfer by generating the start condition (in
454 * try_address) and transmits the address in the necessary format to handle
455 * reads, writes as well as 10bit-addresses.
456 * returns:
457 * 0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set
458 * -x an error occurred (like: -EREMOTEIO if the device did not answer, or
459 * -ETIMEDOUT, for example if the lines are stuck...)
460 */
bit_doAddress(struct i2c_adapter * i2c_adap,struct i2c_msg * msg)461 static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
462 {
463 unsigned short flags = msg->flags;
464 unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
465 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
466
467 unsigned char addr;
468 int ret, retries;
469
470 retries = nak_ok ? 0 : i2c_adap->retries;
471
472 if (flags & I2C_M_TEN) {
473 /* a ten bit address */
474 addr = 0xf0 | ((msg->addr >> 7) & 0x03);
475 bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr);
476 /* try extended address code...*/
477 ret = try_address(i2c_adap, addr, retries);
478 if ((ret != 1) && !nak_ok) {
479 dev_err(&i2c_adap->dev,
480 "died at extended address code\n");
481 return -EREMOTEIO;
482 }
483 /* the remaining 8 bit address */
484 ret = i2c_outb(i2c_adap, msg->addr & 0x7f);
485 if ((ret != 1) && !nak_ok) {
486 /* the chip did not ack / xmission error occurred */
487 dev_err(&i2c_adap->dev, "died at 2nd address code\n");
488 return -EREMOTEIO;
489 }
490 if (flags & I2C_M_RD) {
491 bit_dbg(3, &i2c_adap->dev, "emitting repeated "
492 "start condition\n");
493 i2c_repstart(adap);
494 /* okay, now switch into reading mode */
495 addr |= 0x01;
496 ret = try_address(i2c_adap, addr, retries);
497 if ((ret != 1) && !nak_ok) {
498 dev_err(&i2c_adap->dev,
499 "died at repeated address code\n");
500 return -EREMOTEIO;
501 }
502 }
503 } else { /* normal 7bit address */
504 addr = msg->addr << 1;
505 if (flags & I2C_M_RD)
506 addr |= 1;
507 if (flags & I2C_M_REV_DIR_ADDR)
508 addr ^= 1;
509 ret = try_address(i2c_adap, addr, retries);
510 if ((ret != 1) && !nak_ok)
511 return -ENXIO;
512 }
513
514 return 0;
515 }
516
bit_xfer(struct i2c_adapter * i2c_adap,struct i2c_msg msgs[],int num)517 static int bit_xfer(struct i2c_adapter *i2c_adap,
518 struct i2c_msg msgs[], int num)
519 {
520 struct i2c_msg *pmsg;
521 struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
522 int i, ret;
523 unsigned short nak_ok;
524
525 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
526 i2c_start(adap);
527 for (i = 0; i < num; i++) {
528 pmsg = &msgs[i];
529 nak_ok = pmsg->flags & I2C_M_IGNORE_NAK;
530 if (!(pmsg->flags & I2C_M_NOSTART)) {
531 if (i) {
532 bit_dbg(3, &i2c_adap->dev, "emitting "
533 "repeated start condition\n");
534 i2c_repstart(adap);
535 }
536 ret = bit_doAddress(i2c_adap, pmsg);
537 if ((ret != 0) && !nak_ok) {
538 bit_dbg(1, &i2c_adap->dev, "NAK from "
539 "device addr 0x%02x msg #%d\n",
540 msgs[i].addr, i);
541 goto bailout;
542 }
543 }
544 if (pmsg->flags & I2C_M_RD) {
545 /* read bytes into buffer*/
546 ret = readbytes(i2c_adap, pmsg);
547 if (ret >= 1)
548 bit_dbg(2, &i2c_adap->dev, "read %d byte%s\n",
549 ret, ret == 1 ? "" : "s");
550 if (ret < pmsg->len) {
551 if (ret >= 0)
552 ret = -EREMOTEIO;
553 goto bailout;
554 }
555 } else {
556 /* write bytes from buffer */
557 ret = sendbytes(i2c_adap, pmsg);
558 if (ret >= 1)
559 bit_dbg(2, &i2c_adap->dev, "wrote %d byte%s\n",
560 ret, ret == 1 ? "" : "s");
561 if (ret < pmsg->len) {
562 if (ret >= 0)
563 ret = -EREMOTEIO;
564 goto bailout;
565 }
566 }
567 }
568 ret = i;
569
570 bailout:
571 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
572 i2c_stop(adap);
573 return ret;
574 }
575
bit_func(struct i2c_adapter * adap)576 static u32 bit_func(struct i2c_adapter *adap)
577 {
578 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
579 I2C_FUNC_SMBUS_READ_BLOCK_DATA |
580 I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
581 I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
582 }
583
584
585 /* -----exported algorithm data: ------------------------------------- */
586
587 static const struct i2c_algorithm i2c_bit_algo = {
588 .master_xfer = bit_xfer,
589 .functionality = bit_func,
590 };
591
592 /*
593 * registering functions to load algorithms at runtime
594 */
i2c_bit_prepare_bus(struct i2c_adapter * adap)595 static int i2c_bit_prepare_bus(struct i2c_adapter *adap)
596 {
597 struct i2c_algo_bit_data *bit_adap = adap->algo_data;
598
599 if (bit_test) {
600 int ret = test_bus(bit_adap, adap->name);
601 if (ret < 0)
602 return -ENODEV;
603 }
604
605 /* register new adapter to i2c module... */
606 adap->algo = &i2c_bit_algo;
607
608 adap->timeout = 100; /* default values, should */
609 adap->retries = 3; /* be replaced by defines */
610
611 return 0;
612 }
613
i2c_bit_add_bus(struct i2c_adapter * adap)614 int i2c_bit_add_bus(struct i2c_adapter *adap)
615 {
616 int err;
617
618 err = i2c_bit_prepare_bus(adap);
619 if (err)
620 return err;
621
622 return i2c_add_adapter(adap);
623 }
624 EXPORT_SYMBOL(i2c_bit_add_bus);
625
i2c_bit_add_numbered_bus(struct i2c_adapter * adap)626 int i2c_bit_add_numbered_bus(struct i2c_adapter *adap)
627 {
628 int err;
629
630 err = i2c_bit_prepare_bus(adap);
631 if (err)
632 return err;
633
634 return i2c_add_numbered_adapter(adap);
635 }
636 EXPORT_SYMBOL(i2c_bit_add_numbered_bus);
637
638 MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
639 MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm");
640 MODULE_LICENSE("GPL");
641