1 // SPDX-License-Identifier: GPL-2.0+
3  * i2c-algo-bit.c: i2c driver algorithms for bit-shift adapters
5  *   Copyright (C) 1995-2000 Simon G. Vogl
17 #include <linux/i2c-algo-bit.h>
20 /* ----- global defines ----------------------------------------------- */
33 /* ----- global variables ---------------------------------------------	*/
35 static int bit_test;	/* see if the line-setting functions work	*/
37 MODULE_PARM_DESC(bit_test, "lines testing - 0 off; 1 report; 2 fail if stuck");
43 		 "debug level - 0 off; 1 normal; 2 verbose; 3 very verbose");
46 /* --- setting states on the bus with the right timing: ---------------	*/
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)
56 	udelay((adap->udelay + 1) / 2);  in sdalo()
62 	udelay((adap->udelay + 1) / 2);  in sdahi()
68 	udelay(adap->udelay / 2);  in scllo()
82 	if (!adap->getscl)  in sclhi()
92 		if (time_after(jiffies, start + adap->timeout)) {  in sclhi()
98 			return -ETIMEDOUT;  in sclhi()
104 		pr_debug("i2c-algo-bit: needed %ld jiffies for SCL to go high\n",  in sclhi()
105 			 jiffies - start);  in sclhi()
109 	udelay(adap->udelay);  in sclhi()
114 /* --- other auxiliary functions --------------------------------------	*/
119 	udelay(adap->udelay);  in i2c_start()
129 	udelay(adap->udelay);  in i2c_repstart()
140 	udelay(adap->udelay);  in i2c_stop()
150  * -ETIMEDOUT if an error occurred (while raising the scl line)
157 	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;  in i2c_outb()
160 	for (i = 7; i >= 0; i--) {  in i2c_outb()
163 		udelay((adap->udelay + 1) / 2);  in i2c_outb()
165 			bit_dbg(1, &i2c_adap->dev,  in i2c_outb()
168 			return -ETIMEDOUT;  in i2c_outb()
171 		 * if (sb && !getsda(adap)) -> ouch! Get out of here.  in i2c_outb()
180 		bit_dbg(1, &i2c_adap->dev,  in i2c_outb()
182 		return -ETIMEDOUT;  in i2c_outb()
188 	ack = !getsda(adap);    /* ack: sda is pulled low -> success */  in i2c_outb()
189 	bit_dbg(2, &i2c_adap->dev, "i2c_outb: 0x%02x %s\n", (int)c,  in i2c_outb()
204 	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;  in i2c_inb()
210 			bit_dbg(1, &i2c_adap->dev,  in i2c_inb()
212 				7 - i);  in i2c_inb()
213 			return -ETIMEDOUT;  in i2c_inb()
219 		udelay(i == 7 ? adap->udelay / 2 : adap->udelay);  in i2c_inb()
226  * Sanity check for the adapter hardware - check the reaction of
227  * the bus lines only if it seems to be idle.
231 	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;  in test_bus()
232 	const char *name = i2c_adap->name;  in test_bus()
235 	if (adap->pre_xfer) {  in test_bus()
236 		ret = adap->pre_xfer(i2c_adap);  in test_bus()
238 			return -ENODEV;  in test_bus()
241 	if (adap->getscl == NULL)  in test_bus()
245 	scl = (adap->getscl == NULL) ? 1 : getscl(adap);  in test_bus()
255 	scl = (adap->getscl == NULL) ? 1 : getscl(adap);  in test_bus()
269 	scl = (adap->getscl == NULL) ? 1 : getscl(adap);  in test_bus()
283 	scl = (adap->getscl == NULL) ? 0 : getscl(adap);  in test_bus()
297 	scl = (adap->getscl == NULL) ? 1 : getscl(adap);  in test_bus()
309 	if (adap->post_xfer)  in test_bus()
310 		adap->post_xfer(i2c_adap);  in test_bus()
318 	if (adap->post_xfer)  in test_bus()
319 		adap->post_xfer(i2c_adap);  in test_bus()
321 	return -ENODEV;  in test_bus()
324 /* ----- Utility functions
332  * -x transmission error
337 	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;  in try_address()
344 		bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");  in try_address()
346 		udelay(adap->udelay);  in try_address()
348 		bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");  in try_address()
352 		bit_dbg(1, &i2c_adap->dev,  in try_address()
361 	const unsigned char *temp = msg->buf;  in sendbytes()
362 	int count = msg->len;  in sendbytes()
363 	unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;  in sendbytes()
372 			count--;  in sendbytes()
381 			dev_err(&i2c_adap->dev, "sendbytes: NAK bailout.\n");  in sendbytes()
382 			return -EIO;  in sendbytes()
392 			dev_err(&i2c_adap->dev, "sendbytes: error %d\n",  in sendbytes()
402 	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;  in acknak()
407 	udelay((adap->udelay + 1) / 2);  in acknak()
409 		dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n");  in acknak()
410 		return -ETIMEDOUT;  in acknak()
420 	unsigned char *temp = msg->buf;  in readbytes()
421 	int count = msg->len;  in readbytes()
422 	const unsigned flags = msg->flags;  in readbytes()
434 		count--;  in readbytes()
442 				dev_err(&i2c_adap->dev,  in readbytes()
445 				return -EPROTO;  in readbytes()
451 			msg->len += inval;  in readbytes()
454 		bit_dbg(2, &i2c_adap->dev, "readbytes: 0x%02x %s\n",  in readbytes()
471  * reads, writes as well as 10bit-addresses.
474  * -x an error occurred (like: -ENXIO if the device did not answer, or
475  *	-ETIMEDOUT, for example if the lines are stuck...)
479 	unsigned short flags = msg->flags;  in bit_doAddress()
480 	unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;  in bit_doAddress()
481 	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;  in bit_doAddress()
486 	retries = nak_ok ? 0 : i2c_adap->retries;  in bit_doAddress()
490 		addr = 0xf0 | ((msg->addr >> 7) & 0x06);  in bit_doAddress()
491 		bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr);  in bit_doAddress()
495 			dev_err(&i2c_adap->dev,  in bit_doAddress()
497 			return -ENXIO;  in bit_doAddress()
500 		ret = i2c_outb(i2c_adap, msg->addr & 0xff);  in bit_doAddress()
503 			dev_err(&i2c_adap->dev, "died at 2nd address code\n");  in bit_doAddress()
504 			return -ENXIO;  in bit_doAddress()
507 			bit_dbg(3, &i2c_adap->dev,  in bit_doAddress()
514 				dev_err(&i2c_adap->dev,  in bit_doAddress()
516 				return -EIO;  in bit_doAddress()
525 			return -ENXIO;  in bit_doAddress()
535 	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;  in bit_xfer()
539 	if (adap->pre_xfer) {  in bit_xfer()
540 		ret = adap->pre_xfer(i2c_adap);  in bit_xfer()
545 	bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");  in bit_xfer()
549 		nak_ok = pmsg->flags & I2C_M_IGNORE_NAK;  in bit_xfer()
550 		if (!(pmsg->flags & I2C_M_NOSTART)) {  in bit_xfer()
552 				if (msgs[i - 1].flags & I2C_M_STOP) {  in bit_xfer()
553 					bit_dbg(3, &i2c_adap->dev,  in bit_xfer()
558 					bit_dbg(3, &i2c_adap->dev,  in bit_xfer()
565 				bit_dbg(1, &i2c_adap->dev,  in bit_xfer()
571 		if (pmsg->flags & I2C_M_RD) {  in bit_xfer()
575 				bit_dbg(2, &i2c_adap->dev, "read %d byte%s\n",  in bit_xfer()
577 			if (ret < pmsg->len) {  in bit_xfer()
579 					ret = -EIO;  in bit_xfer()
586 				bit_dbg(2, &i2c_adap->dev, "wrote %d byte%s\n",  in bit_xfer()
588 			if (ret < pmsg->len) {  in bit_xfer()
590 					ret = -EIO;  in bit_xfer()
598 	bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");  in bit_xfer()
601 	if (adap->post_xfer)  in bit_xfer()
602 		adap->post_xfer(i2c_adap);  in bit_xfer()
615 	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;  in bit_xfer_atomic()
617 	if (!adap->can_do_atomic)  in bit_xfer_atomic()
618 		dev_warn(&i2c_adap->dev, "not flagged for atomic transfers\n");  in bit_xfer_atomic()
630 /* -----exported algorithm data: -------------------------------------	*/
649 	struct i2c_algo_bit_data *bit_adap = adap->algo_data;  in __i2c_bit_add_bus()
655 			return -ENODEV;  in __i2c_bit_add_bus()
659 	adap->algo = &i2c_bit_algo;  in __i2c_bit_add_bus()
660 	adap->retries = 3;  in __i2c_bit_add_bus()
661 	if (bit_adap->getscl == NULL)  in __i2c_bit_add_bus()
662 		adap->quirks = &i2c_bit_quirk_no_clk_stretch;  in __i2c_bit_add_bus()
665 	 * We tried forcing SCL/SDA to an initial state here. But that caused a  in __i2c_bit_add_bus()
674 	if (bit_adap->getscl == NULL) {  in __i2c_bit_add_bus()
675 		dev_warn(&adap->dev, "Not I2C compliant: can't read SCL\n");  in __i2c_bit_add_bus()
676 		dev_warn(&adap->dev, "Bus may be unreliable\n");  in __i2c_bit_add_bus()
693 MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
694 MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm");