xref: /linux/drivers/i2c/algos/i2c-algo-pcf.c (revision d30c1683aaecb93d2ab95685dc4300a33d3cea7a) 
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * i2c-algo-pcf.c i2c driver algorithms for PCF8584 adapters
4  *
5  *   Copyright (C) 1995-1997 Simon G. Vogl
6  *		   1998-2000 Hans Berglund
7  *
8  * With some changes from Kyösti Mälkki <kmalkki@cc.hut.fi> and
9  * Frodo Looijaard <frodol@dds.nl>, and also from Martin Bailey
10  * <mbailey@littlefeet-inc.com>
11  *
12  * Partially rewriten by Oleg I. Vdovikin <vdovikin@jscc.ru> to handle multiple
13  * messages, proper stop/repstart signaling during receive, added detect code
14  */
15 
16 #include <linux/kernel.h>
17 #include <linux/module.h>
18 #include <linux/delay.h>
19 #include <linux/errno.h>
20 #include <linux/i2c.h>
21 #include <linux/i2c-algo-pcf.h>
22 #include <linux/string_choices.h>
23 #include "i2c-algo-pcf.h"
24 
25 
26 #define DEF_TIMEOUT 16
27 
28 /* setting states on the bus with the right timing: */
29 
30 #define set_pcf(adap, ctl, val) adap->setpcf(adap->data, ctl, val)
31 #define get_pcf(adap, ctl) adap->getpcf(adap->data, ctl)
32 #define get_own(adap) adap->getown(adap->data)
33 #define get_clock(adap) adap->getclock(adap->data)
34 #define i2c_outb(adap, val) adap->setpcf(adap->data, 0, val)
35 #define i2c_inb(adap) adap->getpcf(adap->data, 0)
36 
37 /* other auxiliary functions */
38 
39 static void i2c_start(struct i2c_algo_pcf_data *adap)
40 {
41 	set_pcf(adap, 1, I2C_PCF_START);
42 }
43 
44 static void i2c_repstart(struct i2c_algo_pcf_data *adap)
45 {
46 	set_pcf(adap, 1, I2C_PCF_REPSTART);
47 }
48 
49 static void i2c_stop(struct i2c_algo_pcf_data *adap)
50 {
51 	set_pcf(adap, 1, I2C_PCF_STOP);
52 }
53 
54 static void handle_lab(struct i2c_algo_pcf_data *adap, const int *status)
55 {
56 	/*
57 	 * Cleanup from LAB -- reset and enable ESO.
58 	 * This resets the PCF8584; since we've lost the bus, no
59 	 * further attempts should be made by callers to clean up
60 	 * (no i2c_stop() etc.)
61 	 */
62 	set_pcf(adap, 1, I2C_PCF_PIN);
63 	set_pcf(adap, 1, I2C_PCF_ESO);
64 	/*
65 	 * We pause for a time period sufficient for any running
66 	 * I2C transaction to complete -- the arbitration logic won't
67 	 * work properly until the next START is seen.
68 	 * It is assumed the bus driver or client has set a proper value.
69 	 *
70 	 * REVISIT: should probably use msleep instead of mdelay if we
71 	 * know we can sleep.
72 	 */
73 	if (adap->lab_mdelay)
74 		mdelay(adap->lab_mdelay);
75 
76 }
77 
78 static int wait_for_bb(struct i2c_algo_pcf_data *adap)
79 {
80 
81 	int timeout = DEF_TIMEOUT;
82 	int status;
83 
84 	status = get_pcf(adap, 1);
85 
86 	while (!(status & I2C_PCF_BB) && --timeout) {
87 		udelay(100); /* wait for 100 us */
88 		status = get_pcf(adap, 1);
89 	}
90 
91 	if (timeout == 0) {
92 		printk(KERN_ERR "Timeout waiting for Bus Busy\n");
93 		return -ETIMEDOUT;
94 	}
95 
96 	return 0;
97 }
98 
99 static int wait_for_pin(struct i2c_algo_pcf_data *adap, int *status)
100 {
101 
102 	int timeout = DEF_TIMEOUT;
103 
104 	*status = get_pcf(adap, 1);
105 
106 	while ((*status & I2C_PCF_PIN) && --timeout) {
107 		adap->waitforpin(adap->data);
108 		*status = get_pcf(adap, 1);
109 	}
110 	if (*status & I2C_PCF_LAB) {
111 		handle_lab(adap, status);
112 		return -EINTR;
113 	}
114 
115 	if (timeout == 0)
116 		return -ETIMEDOUT;
117 
118 	return 0;
119 }
120 
121 /*
122  * This should perform the 'PCF8584 initialization sequence' as described
123  * in the Philips IC12 data book (1995, Aug 29).
124  * There should be a 30 clock cycle wait after reset, I assume this
125  * has been fulfilled.
126  * There should be a delay at the end equal to the longest I2C message
127  * to synchronize the BB-bit (in multimaster systems). How long is
128  * this? I assume 1 second is always long enough.
129  *
130  * vdovikin: added detect code for PCF8584
131  */
132 static int pcf_init_8584(struct i2c_algo_pcf_data *adap)
133 {
134 	unsigned char temp;
135 
136 	/* S1=0x80: S0 selected, serial interface off */
137 	set_pcf(adap, 1, I2C_PCF_PIN);
138 	/*
139 	 * check to see S1 now used as R/W ctrl -
140 	 * PCF8584 does that when ESO is zero
141 	 */
142 	temp = get_pcf(adap, 1);
143 	if ((temp & 0x7f) != 0)
144 		return -ENXIO; /* definitely not PCF8584 */
145 
146 	/* load own address in S0, effective address is (own << 1) */
147 	i2c_outb(adap, get_own(adap));
148 	/* check it's really written */
149 	temp = i2c_inb(adap);
150 	if (temp != get_own(adap))
151 		return -ENXIO;
152 
153 	/* S1=0xA0, next byte in S2 */
154 	set_pcf(adap, 1, I2C_PCF_PIN | I2C_PCF_ES1);
155 	/* check to see S2 now selected */
156 	temp = get_pcf(adap, 1);
157 	if ((temp & 0x7f) != I2C_PCF_ES1)
158 		return -ENXIO;
159 
160 	/* load clock register S2 */
161 	i2c_outb(adap, get_clock(adap));
162 	/* check it's really written, the only 5 lowest bits does matter */
163 	temp = i2c_inb(adap);
164 	if ((temp & 0x1f) != get_clock(adap))
165 		return -ENXIO;
166 
167 	/* Enable serial interface, idle, S0 selected */
168 	set_pcf(adap, 1, I2C_PCF_IDLE);
169 
170 	/* check to see PCF is really idled and we can access status register */
171 	temp = get_pcf(adap, 1);
172 	if (temp != (I2C_PCF_PIN | I2C_PCF_BB))
173 		return -ENXIO;
174 
175 	printk(KERN_DEBUG "i2c-algo-pcf.o: detected and initialized PCF8584.\n");
176 
177 	return 0;
178 }
179 
180 static int pcf_sendbytes(struct i2c_adapter *i2c_adap, const char *buf,
181 			 int count, int last)
182 {
183 	struct i2c_algo_pcf_data *adap = i2c_adap->algo_data;
184 	int wrcount, status, timeout;
185 
186 	for (wrcount = 0; wrcount < count; ++wrcount) {
187 		i2c_outb(adap, buf[wrcount]);
188 		timeout = wait_for_pin(adap, &status);
189 		if (timeout) {
190 			if (timeout == -EINTR)
191 				return -EINTR; /* arbitration lost */
192 
193 			i2c_stop(adap);
194 			dev_err(&i2c_adap->dev, "i2c_write: error - timeout.\n");
195 			return -EREMOTEIO; /* got a better one ?? */
196 		}
197 		if (status & I2C_PCF_LRB) {
198 			i2c_stop(adap);
199 			dev_err(&i2c_adap->dev, "i2c_write: error - no ack.\n");
200 			return -EREMOTEIO; /* got a better one ?? */
201 		}
202 	}
203 	if (last)
204 		i2c_stop(adap);
205 	else
206 		i2c_repstart(adap);
207 
208 	return wrcount;
209 }
210 
211 static int pcf_readbytes(struct i2c_adapter *i2c_adap, char *buf,
212 			 int count, int last)
213 {
214 	int i, status;
215 	struct i2c_algo_pcf_data *adap = i2c_adap->algo_data;
216 	int wfp;
217 
218 	/* increment number of bytes to read by one -- read dummy byte */
219 	for (i = 0; i <= count; i++) {
220 
221 		wfp = wait_for_pin(adap, &status);
222 		if (wfp) {
223 			if (wfp == -EINTR)
224 				return -EINTR; /* arbitration lost */
225 
226 			i2c_stop(adap);
227 			dev_err(&i2c_adap->dev, "pcf_readbytes timed out.\n");
228 			return -1;
229 		}
230 
231 		if ((status & I2C_PCF_LRB) && (i != count)) {
232 			i2c_stop(adap);
233 			dev_err(&i2c_adap->dev, "i2c_read: i2c_inb, No ack.\n");
234 			return -1;
235 		}
236 
237 		if (i == count - 1) {
238 			set_pcf(adap, 1, I2C_PCF_ESO);
239 		} else if (i == count) {
240 			if (last)
241 				i2c_stop(adap);
242 			else
243 				i2c_repstart(adap);
244 		}
245 
246 		if (i)
247 			buf[i - 1] = i2c_inb(adap);
248 		else
249 			i2c_inb(adap); /* dummy read */
250 	}
251 
252 	return i - 1;
253 }
254 
255 
256 static void pcf_send_address(struct i2c_algo_pcf_data *adap,
257 			 struct i2c_msg *msg)
258 {
259 	unsigned char addr = i2c_8bit_addr_from_msg(msg);
260 
261 	if (msg->flags & I2C_M_REV_DIR_ADDR)
262 		addr ^= 1;
263 	i2c_outb(adap, addr);
264 }
265 
266 static int pcf_xfer(struct i2c_adapter *i2c_adap,
267 		    struct i2c_msg *msgs,
268 		    int num)
269 {
270 	struct i2c_algo_pcf_data *adap = i2c_adap->algo_data;
271 	struct i2c_msg *pmsg;
272 	int i;
273 	int timeout, status;
274 
275 	if (adap->xfer_begin)
276 		adap->xfer_begin(adap->data);
277 
278 	/* Check for bus busy */
279 	timeout = wait_for_bb(adap);
280 	if (timeout) {
281 		i = -EIO;
282 		goto out;
283 	}
284 
285 	for (i = 0; i < num; i++) {
286 		int ret;
287 
288 		pmsg = &msgs[i];
289 		pcf_send_address(adap, pmsg);
290 
291 		/* Send START */
292 		if (i == 0)
293 			i2c_start(adap);
294 
295 		/* Wait for PIN (pending interrupt NOT) */
296 		timeout = wait_for_pin(adap, &status);
297 		if (timeout) {
298 			if (timeout == -EINTR) {
299 				/* arbitration lost */
300 				i = -EINTR;
301 				goto out;
302 			}
303 			i2c_stop(adap);
304 			i = -EREMOTEIO;
305 			goto out;
306 		}
307 
308 		/* Check LRB (last rcvd bit - slave ack) */
309 		if (status & I2C_PCF_LRB) {
310 			i2c_stop(adap);
311 			i = -EREMOTEIO;
312 			goto out;
313 		}
314 
315 
316 		if (pmsg->flags & I2C_M_RD) {
317 			ret = pcf_readbytes(i2c_adap, pmsg->buf, pmsg->len,
318 					    (i + 1 == num));
319 		} else {
320 			ret = pcf_sendbytes(i2c_adap, pmsg->buf, pmsg->len,
321 					    (i + 1 == num));
322 		}
323 
324 		if (ret < 0)
325 			goto out;
326 	}
327 
328 out:
329 	if (adap->xfer_end)
330 		adap->xfer_end(adap->data);
331 	return i;
332 }
333 
334 static u32 pcf_func(struct i2c_adapter *adap)
335 {
336 	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
337 	       I2C_FUNC_PROTOCOL_MANGLING;
338 }
339 
340 /* exported algorithm data: */
341 static const struct i2c_algorithm pcf_algo = {
342 	.xfer = pcf_xfer,
343 	.functionality = pcf_func,
344 };
345 
346 /*
347  * registering functions to load algorithms at runtime
348  */
349 int i2c_pcf_add_bus(struct i2c_adapter *adap)
350 {
351 	struct i2c_algo_pcf_data *pcf_adap = adap->algo_data;
352 	int rval;
353 
354 	/* register new adapter to i2c module... */
355 	adap->algo = &pcf_algo;
356 
357 	rval = pcf_init_8584(pcf_adap);
358 	if (rval)
359 		return rval;
360 
361 	rval = i2c_add_adapter(adap);
362 
363 	return rval;
364 }
365 EXPORT_SYMBOL(i2c_pcf_add_bus);
366 
367 MODULE_AUTHOR("Hans Berglund <hb@spacetec.no>");
368 MODULE_DESCRIPTION("I2C-Bus PCF8584 algorithm");
369 MODULE_LICENSE("GPL");
370