1 /* -------------------------------------------------------------------------
2 * i2c-algo-bit.c i2c driver algorithms for bit-shift adapters
3 * -------------------------------------------------------------------------
4 * Copyright (C) 1995-2000 Simon G. Vogl
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.
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.
16 You should have received a copy of the GNU General Public License
17 along with this program; if not, write to the Free Software
18 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
20 * ------------------------------------------------------------------------- */
22 /* With some changes from Frodo Looijaard <frodol@dds.nl>, Kyösti Mälkki
23 <kmalkki@cc.hut.fi> and Jean Delvare <khali@linux-fr.org> */
25 #include <linux/kernel.h>
26 #include <linux/module.h>
27 #include <linux/delay.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>
35 /* ----- global defines ----------------------------------------------- */
38 #define bit_dbg(level, dev, format, args...) \
40 if (i2c_debug >= level) \
41 dev_dbg(dev, format, ##args); \
44 #define bit_dbg(level, dev, format, args...) \
48 /* ----- global variables --------------------------------------------- */
50 static int bit_test
; /* see if the line-setting functions work */
51 module_param(bit_test
, int, S_IRUGO
);
52 MODULE_PARM_DESC(bit_test
, "lines testing - 0 off; 1 report; 2 fail if stuck");
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");
61 /* --- setting states on the bus with the right timing: --------------- */
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)
68 static inline void sdalo(struct i2c_algo_bit_data
*adap
)
71 udelay((adap
->udelay
+ 1) / 2);
74 static inline void sdahi(struct i2c_algo_bit_data
*adap
)
77 udelay((adap
->udelay
+ 1) / 2);
80 static inline void scllo(struct i2c_algo_bit_data
*adap
)
83 udelay(adap
->udelay
/ 2);
87 * Raise scl line, and do checking for delays. This is necessary for slower
90 static int sclhi(struct i2c_algo_bit_data
*adap
)
96 /* Not all adapters have scl sense line... */
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.
107 if (time_after(jiffies
, start
+ adap
->timeout
)) {
108 /* Test one last time, as we may have been preempted
109 * between last check and timeout test.
118 if (jiffies
!= start
&& i2c_debug
>= 3)
119 pr_debug("i2c-algo-bit: needed %ld jiffies for SCL to go "
120 "high\n", jiffies
- start
);
124 udelay(adap
->udelay
);
129 /* --- other auxiliary functions -------------------------------------- */
130 static void i2c_start(struct i2c_algo_bit_data
*adap
)
132 /* assert: scl, sda are high */
134 udelay(adap
->udelay
);
138 static void i2c_repstart(struct i2c_algo_bit_data
*adap
)
140 /* assert: scl is low */
144 udelay(adap
->udelay
);
149 static void i2c_stop(struct i2c_algo_bit_data
*adap
)
151 /* assert: scl is low */
155 udelay(adap
->udelay
);
160 /* send a byte without start cond., look for arbitration,
161 check ackn. from slave */
163 * 1 if the device acknowledged
164 * 0 if the device did not ack
165 * -ETIMEDOUT if an error occurred (while raising the scl line)
167 static int i2c_outb(struct i2c_adapter
*i2c_adap
, unsigned char c
)
172 struct i2c_algo_bit_data
*adap
= i2c_adap
->algo_data
;
174 /* assert: scl is low */
175 for (i
= 7; i
>= 0; i
--) {
178 udelay((adap
->udelay
+ 1) / 2);
179 if (sclhi(adap
) < 0) { /* timed out */
180 bit_dbg(1, &i2c_adap
->dev
, "i2c_outb: 0x%02x, "
181 "timeout at bit #%d\n", (int)c
, i
);
184 /* FIXME do arbitration here:
185 * if (sb && !getsda(adap)) -> ouch! Get out of here.
187 * Report a unique code, so higher level code can retry
188 * the whole (combined) message and *NOT* issue STOP.
193 if (sclhi(adap
) < 0) { /* timeout */
194 bit_dbg(1, &i2c_adap
->dev
, "i2c_outb: 0x%02x, "
195 "timeout at ack\n", (int)c
);
199 /* read ack: SDA should be pulled down by slave, or it may
200 * NAK (usually to report problems with the data we wrote).
202 ack
= !getsda(adap
); /* ack: sda is pulled low -> success */
203 bit_dbg(2, &i2c_adap
->dev
, "i2c_outb: 0x%02x %s\n", (int)c
,
208 /* assert: scl is low (sda undef) */
212 static int i2c_inb(struct i2c_adapter
*i2c_adap
)
214 /* read byte via i2c port, without start/stop sequence */
215 /* acknowledge is sent in i2c_read. */
217 unsigned char indata
= 0;
218 struct i2c_algo_bit_data
*adap
= i2c_adap
->algo_data
;
220 /* assert: scl is low */
222 for (i
= 0; i
< 8; i
++) {
223 if (sclhi(adap
) < 0) { /* timeout */
224 bit_dbg(1, &i2c_adap
->dev
, "i2c_inb: timeout at bit "
232 udelay(i
== 7 ? adap
->udelay
/ 2 : adap
->udelay
);
234 /* assert: scl is low */
239 * Sanity check for the adapter hardware - check the reaction of
240 * the bus lines only if it seems to be idle.
242 static int test_bus(struct i2c_adapter
*i2c_adap
)
244 struct i2c_algo_bit_data
*adap
= i2c_adap
->algo_data
;
245 const char *name
= i2c_adap
->name
;
248 if (adap
->pre_xfer
) {
249 ret
= adap
->pre_xfer(i2c_adap
);
254 if (adap
->getscl
== NULL
)
255 pr_info("%s: Testing SDA only, SCL is not readable\n", name
);
258 scl
= (adap
->getscl
== NULL
) ? 1 : getscl(adap
);
261 "%s: bus seems to be busy (scl=%d, sda=%d)\n",
268 scl
= (adap
->getscl
== NULL
) ? 1 : getscl(adap
);
270 printk(KERN_WARNING
"%s: SDA stuck high!\n", name
);
274 printk(KERN_WARNING
"%s: SCL unexpected low "
275 "while pulling SDA low!\n", name
);
281 scl
= (adap
->getscl
== NULL
) ? 1 : getscl(adap
);
283 printk(KERN_WARNING
"%s: SDA stuck low!\n", name
);
287 printk(KERN_WARNING
"%s: SCL unexpected low "
288 "while pulling SDA high!\n", name
);
294 scl
= (adap
->getscl
== NULL
) ? 0 : getscl(adap
);
296 printk(KERN_WARNING
"%s: SCL stuck high!\n", name
);
300 printk(KERN_WARNING
"%s: SDA unexpected low "
301 "while pulling SCL low!\n", name
);
307 scl
= (adap
->getscl
== NULL
) ? 1 : getscl(adap
);
309 printk(KERN_WARNING
"%s: SCL stuck low!\n", name
);
313 printk(KERN_WARNING
"%s: SDA unexpected low "
314 "while pulling SCL high!\n", name
);
319 adap
->post_xfer(i2c_adap
);
321 pr_info("%s: Test OK\n", name
);
328 adap
->post_xfer(i2c_adap
);
333 /* ----- Utility functions
336 /* try_address tries to contact a chip for a number of
337 * times before it gives up.
340 * 0 chip did not answer
341 * -x transmission error
343 static int try_address(struct i2c_adapter
*i2c_adap
,
344 unsigned char addr
, int retries
)
346 struct i2c_algo_bit_data
*adap
= i2c_adap
->algo_data
;
349 for (i
= 0; i
<= retries
; i
++) {
350 ret
= i2c_outb(i2c_adap
, addr
);
351 if (ret
== 1 || i
== retries
)
353 bit_dbg(3, &i2c_adap
->dev
, "emitting stop condition\n");
355 udelay(adap
->udelay
);
357 bit_dbg(3, &i2c_adap
->dev
, "emitting start condition\n");
361 bit_dbg(1, &i2c_adap
->dev
, "Used %d tries to %s client at "
362 "0x%02x: %s\n", i
+ 1,
363 addr
& 1 ? "read from" : "write to", addr
>> 1,
364 ret
== 1 ? "success" : "failed, timeout?");
368 static int sendbytes(struct i2c_adapter
*i2c_adap
, struct i2c_msg
*msg
)
370 const unsigned char *temp
= msg
->buf
;
371 int count
= msg
->len
;
372 unsigned short nak_ok
= msg
->flags
& I2C_M_IGNORE_NAK
;
377 retval
= i2c_outb(i2c_adap
, *temp
);
379 /* OK/ACK; or ignored NAK */
380 if ((retval
> 0) || (nak_ok
&& (retval
== 0))) {
385 /* A slave NAKing the master means the slave didn't like
386 * something about the data it saw. For example, maybe
387 * the SMBus PEC was wrong.
389 } else if (retval
== 0) {
390 dev_err(&i2c_adap
->dev
, "sendbytes: NAK bailout.\n");
393 /* Timeout; or (someday) lost arbitration
395 * FIXME Lost ARB implies retrying the transaction from
396 * the first message, after the "winning" master issues
397 * its STOP. As a rule, upper layer code has no reason
398 * to know or care about this ... it is *NOT* an error.
401 dev_err(&i2c_adap
->dev
, "sendbytes: error %d\n",
409 static int acknak(struct i2c_adapter
*i2c_adap
, int is_ack
)
411 struct i2c_algo_bit_data
*adap
= i2c_adap
->algo_data
;
413 /* assert: sda is high */
414 if (is_ack
) /* send ack */
416 udelay((adap
->udelay
+ 1) / 2);
417 if (sclhi(adap
) < 0) { /* timeout */
418 dev_err(&i2c_adap
->dev
, "readbytes: ack/nak timeout\n");
425 static int readbytes(struct i2c_adapter
*i2c_adap
, struct i2c_msg
*msg
)
428 int rdcount
= 0; /* counts bytes read */
429 unsigned char *temp
= msg
->buf
;
430 int count
= msg
->len
;
431 const unsigned flags
= msg
->flags
;
434 inval
= i2c_inb(i2c_adap
);
438 } else { /* read timed out */
445 /* Some SMBus transactions require that we receive the
446 transaction length as the first read byte. */
447 if (rdcount
== 1 && (flags
& I2C_M_RECV_LEN
)) {
448 if (inval
<= 0 || inval
> I2C_SMBUS_BLOCK_MAX
) {
449 if (!(flags
& I2C_M_NO_RD_ACK
))
451 dev_err(&i2c_adap
->dev
, "readbytes: invalid "
452 "block length (%d)\n", inval
);
455 /* The original count value accounts for the extra
456 bytes, that is, either 1 for a regular transaction,
457 or 2 for a PEC transaction. */
462 bit_dbg(2, &i2c_adap
->dev
, "readbytes: 0x%02x %s\n",
464 (flags
& I2C_M_NO_RD_ACK
)
466 : (count
? "A" : "NA"));
468 if (!(flags
& I2C_M_NO_RD_ACK
)) {
469 inval
= acknak(i2c_adap
, count
);
477 /* doAddress initiates the transfer by generating the start condition (in
478 * try_address) and transmits the address in the necessary format to handle
479 * reads, writes as well as 10bit-addresses.
481 * 0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set
482 * -x an error occurred (like: -ENXIO if the device did not answer, or
483 * -ETIMEDOUT, for example if the lines are stuck...)
485 static int bit_doAddress(struct i2c_adapter
*i2c_adap
, struct i2c_msg
*msg
)
487 unsigned short flags
= msg
->flags
;
488 unsigned short nak_ok
= msg
->flags
& I2C_M_IGNORE_NAK
;
489 struct i2c_algo_bit_data
*adap
= i2c_adap
->algo_data
;
494 retries
= nak_ok
? 0 : i2c_adap
->retries
;
496 if (flags
& I2C_M_TEN
) {
497 /* a ten bit address */
498 addr
= 0xf0 | ((msg
->addr
>> 7) & 0x06);
499 bit_dbg(2, &i2c_adap
->dev
, "addr0: %d\n", addr
);
500 /* try extended address code...*/
501 ret
= try_address(i2c_adap
, addr
, retries
);
502 if ((ret
!= 1) && !nak_ok
) {
503 dev_err(&i2c_adap
->dev
,
504 "died at extended address code\n");
507 /* the remaining 8 bit address */
508 ret
= i2c_outb(i2c_adap
, msg
->addr
& 0xff);
509 if ((ret
!= 1) && !nak_ok
) {
510 /* the chip did not ack / xmission error occurred */
511 dev_err(&i2c_adap
->dev
, "died at 2nd address code\n");
514 if (flags
& I2C_M_RD
) {
515 bit_dbg(3, &i2c_adap
->dev
, "emitting repeated "
516 "start condition\n");
518 /* okay, now switch into reading mode */
520 ret
= try_address(i2c_adap
, addr
, retries
);
521 if ((ret
!= 1) && !nak_ok
) {
522 dev_err(&i2c_adap
->dev
,
523 "died at repeated address code\n");
527 } else { /* normal 7bit address */
528 addr
= msg
->addr
<< 1;
529 if (flags
& I2C_M_RD
)
531 if (flags
& I2C_M_REV_DIR_ADDR
)
533 ret
= try_address(i2c_adap
, addr
, retries
);
534 if ((ret
!= 1) && !nak_ok
)
541 static int bit_xfer(struct i2c_adapter
*i2c_adap
,
542 struct i2c_msg msgs
[], int num
)
544 struct i2c_msg
*pmsg
;
545 struct i2c_algo_bit_data
*adap
= i2c_adap
->algo_data
;
547 unsigned short nak_ok
;
549 if (adap
->pre_xfer
) {
550 ret
= adap
->pre_xfer(i2c_adap
);
555 bit_dbg(3, &i2c_adap
->dev
, "emitting start condition\n");
557 for (i
= 0; i
< num
; i
++) {
559 nak_ok
= pmsg
->flags
& I2C_M_IGNORE_NAK
;
560 if (!(pmsg
->flags
& I2C_M_NOSTART
)) {
562 bit_dbg(3, &i2c_adap
->dev
, "emitting "
563 "repeated start condition\n");
566 ret
= bit_doAddress(i2c_adap
, pmsg
);
567 if ((ret
!= 0) && !nak_ok
) {
568 bit_dbg(1, &i2c_adap
->dev
, "NAK from "
569 "device addr 0x%02x msg #%d\n",
574 if (pmsg
->flags
& I2C_M_RD
) {
575 /* read bytes into buffer*/
576 ret
= readbytes(i2c_adap
, pmsg
);
578 bit_dbg(2, &i2c_adap
->dev
, "read %d byte%s\n",
579 ret
, ret
== 1 ? "" : "s");
580 if (ret
< pmsg
->len
) {
586 /* write bytes from buffer */
587 ret
= sendbytes(i2c_adap
, pmsg
);
589 bit_dbg(2, &i2c_adap
->dev
, "wrote %d byte%s\n",
590 ret
, ret
== 1 ? "" : "s");
591 if (ret
< pmsg
->len
) {
601 bit_dbg(3, &i2c_adap
->dev
, "emitting stop condition\n");
605 adap
->post_xfer(i2c_adap
);
609 static u32
bit_func(struct i2c_adapter
*adap
)
611 return I2C_FUNC_I2C
| I2C_FUNC_NOSTART
| I2C_FUNC_SMBUS_EMUL
|
612 I2C_FUNC_SMBUS_READ_BLOCK_DATA
|
613 I2C_FUNC_SMBUS_BLOCK_PROC_CALL
|
614 I2C_FUNC_10BIT_ADDR
| I2C_FUNC_PROTOCOL_MANGLING
;
618 /* -----exported algorithm data: ------------------------------------- */
620 const struct i2c_algorithm i2c_bit_algo
= {
621 .master_xfer
= bit_xfer
,
622 .functionality
= bit_func
,
624 EXPORT_SYMBOL(i2c_bit_algo
);
627 * registering functions to load algorithms at runtime
629 static int __i2c_bit_add_bus(struct i2c_adapter
*adap
,
630 int (*add_adapter
)(struct i2c_adapter
*))
632 struct i2c_algo_bit_data
*bit_adap
= adap
->algo_data
;
636 ret
= test_bus(adap
);
637 if (bit_test
>= 2 && ret
< 0)
641 /* register new adapter to i2c module... */
642 adap
->algo
= &i2c_bit_algo
;
645 ret
= add_adapter(adap
);
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");
657 int i2c_bit_add_bus(struct i2c_adapter
*adap
)
659 return __i2c_bit_add_bus(adap
, i2c_add_adapter
);
661 EXPORT_SYMBOL(i2c_bit_add_bus
);
663 int i2c_bit_add_numbered_bus(struct i2c_adapter
*adap
)
665 return __i2c_bit_add_bus(adap
, i2c_add_numbered_adapter
);
667 EXPORT_SYMBOL(i2c_bit_add_numbered_bus
);
669 MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
670 MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm");
671 MODULE_LICENSE("GPL");