aboutsummaryrefslogtreecommitdiff
path: root/drivers/i2c/algos/i2c-algo-bit.c
blob: 38319a69bd0a9de978fc688bded38fa3dea90def (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
/* -------------------------------------------------------------------------
 * i2c-algo-bit.c i2c driver algorithms for bit-shift adapters
 * -------------------------------------------------------------------------
 *   Copyright (C) 1995-2000 Simon G. Vogl

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 * ------------------------------------------------------------------------- */

/* With some changes from Frodo Looijaard <frodol@dds.nl>, Kyösti Mälkki
   <kmalkki@cc.hut.fi> and Jean Delvare <khali@linux-fr.org> */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/i2c.h>
#include <linux/i2c-algo-bit.h>


/* ----- global defines ----------------------------------------------- */

#ifdef DEBUG
#define bit_dbg(level, dev, format, args...) \
	do { \
		if (i2c_debug >= level) \
			dev_dbg(dev, format, ##args); \
	} while (0)
#else
#define bit_dbg(level, dev, format, args...) \
	do {} while (0)
#endif /* DEBUG */

/* ----- global variables ---------------------------------------------	*/

static int bit_test;	/* see if the line-setting functions work	*/
module_param(bit_test, bool, 0);
MODULE_PARM_DESC(bit_test, "Test the lines of the bus to see if it is stuck");

#ifdef DEBUG
static int i2c_debug = 1;
module_param(i2c_debug, int, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(i2c_debug,
		 "debug level - 0 off; 1 normal; 2 verbose; 3 very verbose");
#endif

/* --- setting states on the bus with the right timing: ---------------	*/

#define setsda(adap, val)	adap->setsda(adap->data, val)
#define setscl(adap, val)	adap->setscl(adap->data, val)
#define getsda(adap)		adap->getsda(adap->data)
#define getscl(adap)		adap->getscl(adap->data)

static inline void sdalo(struct i2c_algo_bit_data *adap)
{
	setsda(adap, 0);
	udelay((adap->udelay + 1) / 2);
}

static inline void sdahi(struct i2c_algo_bit_data *adap)
{
	setsda(adap, 1);
	udelay((adap->udelay + 1) / 2);
}

static inline void scllo(struct i2c_algo_bit_data *adap)
{
	setscl(adap, 0);
	udelay(adap->udelay / 2);
}

/*
 * Raise scl line, and do checking for delays. This is necessary for slower
 * devices.
 */
static int sclhi(struct i2c_algo_bit_data *adap)
{
	unsigned long start;

	setscl(adap, 1);

	/* Not all adapters have scl sense line... */
	if (!adap->getscl)
		goto done;

	start = jiffies;
	while (!getscl(adap)) {
		/* This hw knows how to read the clock line, so we wait
		 * until it actually gets high.  This is safer as some
		 * chips may hold it low ("clock stretching") while they
		 * are processing data internally.
		 */
		if (time_after(jiffies, start + adap->timeout))
			return -ETIMEDOUT;
		cond_resched();
	}
#ifdef DEBUG
	if (jiffies != start && i2c_debug >= 3)
		pr_debug("i2c-algo-bit: needed %ld jiffies for SCL to go "
			 "high\n", jiffies - start);
#endif

done:
	udelay(adap->udelay);
	return 0;
}


/* --- other auxiliary functions --------------------------------------	*/
static void i2c_start(struct i2c_algo_bit_data *adap)
{
	/* assert: scl, sda are high */
	setsda(adap, 0);
	udelay(adap->udelay);
	scllo(adap);
}

static void i2c_repstart(struct i2c_algo_bit_data *adap)
{
	/* assert: scl is low */
	sdahi(adap);
	sclhi(adap);
	setsda(adap, 0);
	udelay(adap->udelay);
	scllo(adap);
}


static void i2c_stop(struct i2c_algo_bit_data *adap)
{
	/* assert: scl is low */
	sdalo(adap);
	sclhi(adap);
	setsda(adap, 1);
	udelay(adap->udelay);
}



/* send a byte without start cond., look for arbitration,
   check ackn. from slave */
/* returns:
 * 1 if the device acknowledged
 * 0 if the device did not ack
 * -ETIMEDOUT if an error occurred (while raising the scl line)
 */
static int i2c_outb(struct i2c_adapter *i2c_adap, unsigned char c)
{
	int i;
	int sb;
	int ack;
	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;

	/* assert: scl is low */
	for (i = 7; i >= 0; i--) {
		sb = (c >> i) & 1;
		setsda(adap, sb);
		udelay((adap->udelay + 1) / 2);
		if (sclhi(adap) < 0) { /* timed out */
			bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
				"timeout at bit #%d\n", (int)c, i);
			return -ETIMEDOUT;
		}
		/* FIXME do arbitration here:
		 * if (sb && !getsda(adap)) -> ouch! Get out of here.
		 *
		 * Report a unique code, so higher level code can retry
		 * the whole (combined) message and *NOT* issue STOP.
		 */
		scllo(adap);
	}
	sdahi(adap);
	if (sclhi(adap) < 0) { /* timeout */
		bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
			"timeout at ack\n", (int)c);
		return -ETIMEDOUT;
	}

	/* read ack: SDA should be pulled down by slave, or it may
	 * NAK (usually to report problems with the data we wrote).
	 */
	ack = !getsda(adap);    /* ack: sda is pulled low -> success */
	bit_dbg(2, &i2c_adap->dev, "i2c_outb: 0x%02x %s\n", (int)c,
		ack ? "A" : "NA");

	scllo(adap);
	return ack;
	/* assert: scl is low (sda undef) */
}


static int i2c_inb(struct i2c_adapter *i2c_adap)
{
	/* read byte via i2c port, without start/stop sequence	*/
	/* acknowledge is sent in i2c_read.			*/
	int i;
	unsigned char indata = 0;
	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;

	/* assert: scl is low */
	sdahi(adap);
	for (i = 0; i < 8; i++) {
		if (sclhi(adap) < 0) { /* timeout */
			bit_dbg(1, &i2c_adap->dev, "i2c_inb: timeout at bit "
				"#%d\n", 7 - i);
			return -ETIMEDOUT;
		}
		indata *= 2;
		if (getsda(adap))
			indata |= 0x01;
		setscl(adap, 0);
		udelay(i == 7 ? adap->udelay / 2 : adap->udelay);
	}
	/* assert: scl is low */
	return indata;
}

/*
 * Sanity check for the adapter hardware - check the reaction of
 * the bus lines only if it seems to be idle.
 */
static int test_bus(struct i2c_algo_bit_data *adap, char *name)
{
	int scl, sda;

	if (adap->getscl == NULL)
		pr_info("%s: Testing SDA only, SCL is not readable\n", name);

	sda = getsda(adap);
	scl = (adap->getscl == NULL) ? 1 : getscl(adap);
	if (!scl || !sda) {
		printk(KERN_WARNING "%s: bus seems to be busy\n", name);
		goto bailout;
	}

	sdalo(adap);
	sda = getsda(adap);
	scl = (adap->getscl == NULL) ? 1 : getscl(adap);
	if (sda) {
		printk(KERN_WARNING "%s: SDA stuck high!\n", name);
		goto bailout;
	}
	if (!scl) {
		printk(KERN_WARNING "%s: SCL unexpected low "
		       "while pulling SDA low!\n", name);
		goto bailout;
	}

	sdahi(adap);
	sda = getsda(adap);
	scl = (adap->getscl == NULL) ? 1 : getscl(adap);
	if (!sda) {
		printk(KERN_WARNING "%s: SDA stuck low!\n", name);
		goto bailout;
	}
	if (!scl) {
		printk(KERN_WARNING "%s: SCL unexpected low "
		       "while pulling SDA high!\n", name);
		goto bailout;
	}

	scllo(adap);
	sda = getsda(adap);
	scl = (adap->getscl == NULL) ? 0 : getscl(adap);
	if (scl) {
		printk(KERN_WARNING "%s: SCL stuck high!\n", name);
		goto bailout;
	}
	if (!sda) {
		printk(KERN_WARNING "%s: SDA unexpected low "
		       "while pulling SCL low!\n", name);
		goto bailout;
	}

	sclhi(adap);
	sda = getsda(adap);
	scl = (adap->getscl == NULL) ? 1 : getscl(adap);
	if (!scl) {
		printk(KERN_WARNING "%s: SCL stuck low!\n", name);
		goto bailout;
	}
	if (!sda) {
		printk(KERN_WARNING "%s: SDA unexpected low "
		       "while pulling SCL high!\n", name);
		goto bailout;
	}
	pr_info("%s: Test OK\n", name);
	return 0;
bailout:
	sdahi(adap);
	sclhi(adap);
	return -ENODEV;
}

/* ----- Utility functions
 */

/* try_address tries to contact a chip for a number of
 * times before it gives up.
 * return values:
 * 1 chip answered
 * 0 chip did not answer
 * -x transmission error
 */
static int try_address(struct i2c_adapter *i2c_adap,
		       unsigned char addr, int retries)
{
	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
	int i, ret = 0;

	for (i = 0; i <= retries; i++) {
		ret = i2c_outb(i2c_adap, addr);
		if (ret == 1 || i == retries)
			break;
		bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
		i2c_stop(adap);
		udelay(adap->udelay);
		yield();
		bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
		i2c_start(adap);
	}
	if (i && ret)
		bit_dbg(1, &i2c_adap->dev, "Used %d tries to %s client at "
			"0x%02x: %s\n", i + 1,
			addr & 1 ? "read from" : "write to", addr >> 1,
			ret == 1 ? "success" : "failed, timeout?");
	return ret;
}

static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
{
	const unsigned char *temp = msg->buf;
	int count = msg->len;
	unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
	int retval;
	int wrcount = 0;

	while (count > 0) {
		retval = i2c_outb(i2c_adap, *temp);

		/* OK/ACK; or ignored NAK */
		if ((retval > 0) || (nak_ok && (retval == 0))) {
			count--;
			temp++;
			wrcount++;

		/* A slave NAKing the master means the slave didn't like
		 * something about the data it saw.  For example, maybe
		 * the SMBus PEC was wrong.
		 */
		} else if (retval == 0) {
			dev_err(&i2c_adap->dev, "sendbytes: NAK bailout.\n");
			return -EIO;

		/* Timeout; or (someday) lost arbitration
		 *
		 * FIXME Lost ARB implies retrying the transaction from
		 * the first message, after the "winning" master issues
		 * its STOP.  As a rule, upper layer code has no reason
		 * to know or care about this ... it is *NOT* an error.
		 */
		} else {
			dev_err(&i2c_adap->dev, "sendbytes: error %d\n",
					retval);
			return retval;
		}
	}
	return wrcount;
}

static int acknak(struct i2c_adapter *i2c_adap, int is_ack)
{
	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;

	/* assert: sda is high */
	if (is_ack)		/* send ack */
		setsda(adap, 0);
	udelay((adap->udelay + 1) / 2);
	if (sclhi(adap) < 0) {	/* timeout */
		dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n");
		return -ETIMEDOUT;
	}
	scllo(adap);
	return 0;
}

static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
{
	int inval;
	int rdcount = 0;	/* counts bytes read */
	unsigned char *temp = msg->buf;
	int count = msg->len;
	const unsigned flags = msg->flags;

	while (count > 0) {
		inval = i2c_inb(i2c_adap);
		if (inval >= 0) {
			*temp = inval;
			rdcount++;
		} else {   /* read timed out */
			break;
		}

		temp++;
		count--;

		/* Some SMBus transactions require that we receive the
		   transaction length as the first read byte. */
		if (rdcount == 1 && (flags & I2C_M_RECV_LEN)) {
			if (inval <= 0 || inval > I2C_SMBUS_BLOCK_MAX) {
				if (!(flags & I2C_M_NO_RD_ACK))
					acknak(i2c_adap, 0);
				dev_err(&i2c_adap->dev, "readbytes: invalid "
					"block length (%d)\n", inval);
				return -EREMOTEIO;
			}
			/* The original count value accounts for the extra
			   bytes, that is, either 1 for a regular transaction,
			   or 2 for a PEC transaction. */
			count += inval;
			msg->len += inval;
		}

		bit_dbg(2, &i2c_adap->dev, "readbytes: 0x%02x %s\n",
			inval,
			(flags & I2C_M_NO_RD_ACK)
				? "(no ack/nak)"
				: (count ? "A" : "NA"));

		if (!(flags & I2C_M_NO_RD_ACK)) {
			inval = acknak(i2c_adap, count);
			if (inval < 0)
				return inval;
		}
	}
	return rdcount;
}

/* doAddress initiates the transfer by generating the start condition (in
 * try_address) and transmits the address in the necessary format to handle
 * reads, writes as well as 10bit-addresses.
 * returns:
 *  0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set
 * -x an error occurred (like: -EREMOTEIO if the device did not answer, or
 *	-ETIMEDOUT, for example if the lines are stuck...)
 */
static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
{
	unsigned short flags = msg->flags;
	unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;

	unsigned char addr;
	int ret, retries;

	retries = nak_ok ? 0 : i2c_adap->retries;

	if (flags & I2C_M_TEN) {
		/* a ten bit address */
		addr = 0xf0 | ((msg->addr >> 7) & 0x03);
		bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr);
		/* try extended address code...*/
		ret = try_address(i2c_adap, addr, retries);
		if ((ret != 1) && !nak_ok)  {
			dev_err(&i2c_adap->dev,
				"died at extended address code\n");
			return -EREMOTEIO;
		}
		/* the remaining 8 bit address */
		ret = i2c_outb(i2c_adap, msg->addr & 0x7f);
		if ((ret != 1) && !nak_ok) {
			/* the chip did not ack / xmission error occurred */
			dev_err(&i2c_adap->dev, "died at 2nd address code\n");
			return -EREMOTEIO;
		}
		if (flags & I2C_M_RD) {
			bit_dbg(3, &i2c_adap->dev, "emitting repeated "
				"start condition\n");
			i2c_repstart(adap);
			/* okay, now switch into reading mode */
			addr |= 0x01;
			ret = try_address(i2c_adap, addr, retries);
			if ((ret != 1) && !nak_ok) {
				dev_err(&i2c_adap->dev,
					"died at repeated address code\n");
				return -EREMOTEIO;
			}
		}
	} else {		/* normal 7bit address	*/
		addr = msg->addr << 1;
		if (flags & I2C_M_RD)
			addr |= 1;
		if (flags & I2C_M_REV_DIR_ADDR)
			addr ^= 1;
		ret = try_address(i2c_adap, addr, retries);
		if ((ret != 1) && !nak_ok)
			return -ENXIO;
	}

	return 0;
}

static int bit_xfer(struct i2c_adapter *i2c_adap,
		    struct i2c_msg msgs[], int num)
{
	struct i2c_msg *pmsg;
	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
	int i, ret;
	unsigned short nak_ok;

	if (adap->pre_xfer) {
		ret = adap->pre_xfer(i2c_adap);
		if (ret < 0)
			return ret;
	}

	bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
	i2c_start(adap);
	for (i = 0; i < num; i++) {
		pmsg = &msgs[i];
		nak_ok = pmsg->flags & I2C_M_IGNORE_NAK;
		if (!(pmsg->flags & I2C_M_NOSTART)) {
			if (i) {
				bit_dbg(3, &i2c_adap->dev, "emitting "
					"repeated start condition\n");
				i2c_repstart(adap);
			}
			ret = bit_doAddress(i2c_adap, pmsg);
			if ((ret != 0) && !nak_ok) {
				bit_dbg(1, &i2c_adap->dev, "NAK from "
					"device addr 0x%02x msg #%d\n",
					msgs[i].addr, i);
				goto bailout;
			}
		}
		if (pmsg->flags & I2C_M_RD) {
			/* read bytes into buffer*/
			ret = readbytes(i2c_adap, pmsg);
			if (ret >= 1)
				bit_dbg(2, &i2c_adap->dev, "read %d byte%s\n",
					ret, ret == 1 ? "" : "s");
			if (ret < pmsg->len) {
				if (ret >= 0)
					ret = -EREMOTEIO;
				goto bailout;
			}
		} else {
			/* write bytes from buffer */
			ret = sendbytes(i2c_adap, pmsg);
			if (ret >= 1)
				bit_dbg(2, &i2c_adap->dev, "wrote %d byte%s\n",
					ret, ret == 1 ? "" : "s");
			if (ret < pmsg->len) {
				if (ret >= 0)
					ret = -EREMOTEIO;
				goto bailout;
			}
		}
	}
	ret = i;

bailout:
	bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
	i2c_stop(adap);

	if (adap->post_xfer)
		adap->post_xfer(i2c_adap);
	return ret;
}

static u32 bit_func(struct i2c_adapter *adap)
{
	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
	       I2C_FUNC_SMBUS_READ_BLOCK_DATA |
	       I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
	       I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
}


/* -----exported algorithm data: -------------------------------------	*/

static const struct i2c_algorithm i2c_bit_algo = {
	.master_xfer	= bit_xfer,
	.functionality	= bit_func,
};

/*
 * registering functions to load algorithms at runtime
 */
static int __i2c_bit_add_bus(struct i2c_adapter *adap,
			     int (*add_adapter)(struct i2c_adapter *))
{
	struct i2c_algo_bit_data *bit_adap = adap->algo_data;
	int ret;

	if (bit_test) {
		ret = test_bus(bit_adap, adap->name);
		if (ret < 0)
			return -ENODEV;
	}

	/* register new adapter to i2c module... */
	adap->algo = &i2c_bit_algo;
	adap->retries = 3;

	ret = add_adapter(adap);
	if (ret < 0)
		return ret;

	/* Complain if SCL can't be read */
	if (bit_adap->getscl == NULL) {
		dev_warn(&adap->dev, "Not I2C compliant: can't read SCL\n");
		dev_warn(&adap->dev, "Bus may be unreliable\n");
	}
	return 0;
}

int i2c_bit_add_bus(struct i2c_adapter *adap)
{
	return __i2c_bit_add_bus(adap, i2c_add_adapter);
}
EXPORT_SYMBOL(i2c_bit_add_bus);

int i2c_bit_add_numbered_bus(struct i2c_adapter *adap)
{
	return __i2c_bit_add_bus(adap, i2c_add_numbered_adapter);
}
EXPORT_SYMBOL(i2c_bit_add_numbered_bus);

MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm");
MODULE_LICENSE("GPL");