xref: /openbmc/linux/drivers/w1/w1_io.c (revision c942fddf)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Copyright (c) 2004 Evgeniy Polyakov <zbr@ioremap.net>
4  */
5 
6 #include <asm/io.h>
7 
8 #include <linux/delay.h>
9 #include <linux/moduleparam.h>
10 #include <linux/module.h>
11 
12 #include "w1_internal.h"
13 
14 static int w1_delay_parm = 1;
15 module_param_named(delay_coef, w1_delay_parm, int, 0);
16 
17 static int w1_disable_irqs = 0;
18 module_param_named(disable_irqs, w1_disable_irqs, int, 0);
19 
20 static u8 w1_crc8_table[] = {
21 	0, 94, 188, 226, 97, 63, 221, 131, 194, 156, 126, 32, 163, 253, 31, 65,
22 	157, 195, 33, 127, 252, 162, 64, 30, 95, 1, 227, 189, 62, 96, 130, 220,
23 	35, 125, 159, 193, 66, 28, 254, 160, 225, 191, 93, 3, 128, 222, 60, 98,
24 	190, 224, 2, 92, 223, 129, 99, 61, 124, 34, 192, 158, 29, 67, 161, 255,
25 	70, 24, 250, 164, 39, 121, 155, 197, 132, 218, 56, 102, 229, 187, 89, 7,
26 	219, 133, 103, 57, 186, 228, 6, 88, 25, 71, 165, 251, 120, 38, 196, 154,
27 	101, 59, 217, 135, 4, 90, 184, 230, 167, 249, 27, 69, 198, 152, 122, 36,
28 	248, 166, 68, 26, 153, 199, 37, 123, 58, 100, 134, 216, 91, 5, 231, 185,
29 	140, 210, 48, 110, 237, 179, 81, 15, 78, 16, 242, 172, 47, 113, 147, 205,
30 	17, 79, 173, 243, 112, 46, 204, 146, 211, 141, 111, 49, 178, 236, 14, 80,
31 	175, 241, 19, 77, 206, 144, 114, 44, 109, 51, 209, 143, 12, 82, 176, 238,
32 	50, 108, 142, 208, 83, 13, 239, 177, 240, 174, 76, 18, 145, 207, 45, 115,
33 	202, 148, 118, 40, 171, 245, 23, 73, 8, 86, 180, 234, 105, 55, 213, 139,
34 	87, 9, 235, 181, 54, 104, 138, 212, 149, 203, 41, 119, 244, 170, 72, 22,
35 	233, 183, 85, 11, 136, 214, 52, 106, 43, 117, 151, 201, 74, 20, 246, 168,
36 	116, 42, 200, 150, 21, 75, 169, 247, 182, 232, 10, 84, 215, 137, 107, 53
37 };
38 
w1_delay(unsigned long tm)39 static void w1_delay(unsigned long tm)
40 {
41 	udelay(tm * w1_delay_parm);
42 }
43 
44 static void w1_write_bit(struct w1_master *dev, int bit);
45 static u8 w1_read_bit(struct w1_master *dev);
46 
47 /**
48  * w1_touch_bit() - Generates a write-0 or write-1 cycle and samples the level.
49  * @dev:	the master device
50  * @bit:	0 - write a 0, 1 - write a 0 read the level
51  */
w1_touch_bit(struct w1_master * dev,int bit)52 u8 w1_touch_bit(struct w1_master *dev, int bit)
53 {
54 	if (dev->bus_master->touch_bit)
55 		return dev->bus_master->touch_bit(dev->bus_master->data, bit);
56 	else if (bit)
57 		return w1_read_bit(dev);
58 	else {
59 		w1_write_bit(dev, 0);
60 		return 0;
61 	}
62 }
63 EXPORT_SYMBOL_GPL(w1_touch_bit);
64 
65 /**
66  * w1_write_bit() - Generates a write-0 or write-1 cycle.
67  * @dev:	the master device
68  * @bit:	bit to write
69  *
70  * Only call if dev->bus_master->touch_bit is NULL
71  */
w1_write_bit(struct w1_master * dev,int bit)72 static void w1_write_bit(struct w1_master *dev, int bit)
73 {
74 	unsigned long flags = 0;
75 
76 	if(w1_disable_irqs) local_irq_save(flags);
77 
78 	if (bit) {
79 		dev->bus_master->write_bit(dev->bus_master->data, 0);
80 		w1_delay(6);
81 		dev->bus_master->write_bit(dev->bus_master->data, 1);
82 		w1_delay(64);
83 	} else {
84 		dev->bus_master->write_bit(dev->bus_master->data, 0);
85 		w1_delay(60);
86 		dev->bus_master->write_bit(dev->bus_master->data, 1);
87 		w1_delay(10);
88 	}
89 
90 	if(w1_disable_irqs) local_irq_restore(flags);
91 }
92 
93 /**
94  * w1_pre_write() - pre-write operations
95  * @dev:	the master device
96  *
97  * Pre-write operation, currently only supporting strong pullups.
98  * Program the hardware for a strong pullup, if one has been requested and
99  * the hardware supports it.
100  */
w1_pre_write(struct w1_master * dev)101 static void w1_pre_write(struct w1_master *dev)
102 {
103 	if (dev->pullup_duration &&
104 		dev->enable_pullup && dev->bus_master->set_pullup) {
105 		dev->bus_master->set_pullup(dev->bus_master->data,
106 			dev->pullup_duration);
107 	}
108 }
109 
110 /**
111  * w1_post_write() - post-write options
112  * @dev:	the master device
113  *
114  * Post-write operation, currently only supporting strong pullups.
115  * If a strong pullup was requested, clear it if the hardware supports
116  * them, or execute the delay otherwise, in either case clear the request.
117  */
w1_post_write(struct w1_master * dev)118 static void w1_post_write(struct w1_master *dev)
119 {
120 	if (dev->pullup_duration) {
121 		if (dev->enable_pullup && dev->bus_master->set_pullup)
122 			dev->bus_master->set_pullup(dev->bus_master->data, 0);
123 		else
124 			msleep(dev->pullup_duration);
125 		dev->pullup_duration = 0;
126 	}
127 }
128 
129 /**
130  * w1_write_8() - Writes 8 bits.
131  * @dev:	the master device
132  * @byte:	the byte to write
133  */
w1_write_8(struct w1_master * dev,u8 byte)134 void w1_write_8(struct w1_master *dev, u8 byte)
135 {
136 	int i;
137 
138 	if (dev->bus_master->write_byte) {
139 		w1_pre_write(dev);
140 		dev->bus_master->write_byte(dev->bus_master->data, byte);
141 	}
142 	else
143 		for (i = 0; i < 8; ++i) {
144 			if (i == 7)
145 				w1_pre_write(dev);
146 			w1_touch_bit(dev, (byte >> i) & 0x1);
147 		}
148 	w1_post_write(dev);
149 }
150 EXPORT_SYMBOL_GPL(w1_write_8);
151 
152 
153 /**
154  * w1_read_bit() - Generates a write-1 cycle and samples the level.
155  * @dev:	the master device
156  *
157  * Only call if dev->bus_master->touch_bit is NULL
158  */
w1_read_bit(struct w1_master * dev)159 static u8 w1_read_bit(struct w1_master *dev)
160 {
161 	int result;
162 	unsigned long flags = 0;
163 
164 	/* sample timing is critical here */
165 	local_irq_save(flags);
166 	dev->bus_master->write_bit(dev->bus_master->data, 0);
167 	w1_delay(6);
168 	dev->bus_master->write_bit(dev->bus_master->data, 1);
169 	w1_delay(9);
170 
171 	result = dev->bus_master->read_bit(dev->bus_master->data);
172 	local_irq_restore(flags);
173 
174 	w1_delay(55);
175 
176 	return result & 0x1;
177 }
178 
179 /**
180  * w1_triplet() - * Does a triplet - used for searching ROM addresses.
181  * @dev:	the master device
182  * @bdir:	the bit to write if both id_bit and comp_bit are 0
183  *
184  * Return bits:
185  *  bit 0 = id_bit
186  *  bit 1 = comp_bit
187  *  bit 2 = dir_taken
188  *
189  * If both bits 0 & 1 are set, the search should be restarted.
190  *
191  * Return:        bit fields - see above
192  */
w1_triplet(struct w1_master * dev,int bdir)193 u8 w1_triplet(struct w1_master *dev, int bdir)
194 {
195 	if (dev->bus_master->triplet)
196 		return dev->bus_master->triplet(dev->bus_master->data, bdir);
197 	else {
198 		u8 id_bit   = w1_touch_bit(dev, 1);
199 		u8 comp_bit = w1_touch_bit(dev, 1);
200 		u8 retval;
201 
202 		if (id_bit && comp_bit)
203 			return 0x03;  /* error */
204 
205 		if (!id_bit && !comp_bit) {
206 			/* Both bits are valid, take the direction given */
207 			retval = bdir ? 0x04 : 0;
208 		} else {
209 			/* Only one bit is valid, take that direction */
210 			bdir = id_bit;
211 			retval = id_bit ? 0x05 : 0x02;
212 		}
213 
214 		if (dev->bus_master->touch_bit)
215 			w1_touch_bit(dev, bdir);
216 		else
217 			w1_write_bit(dev, bdir);
218 		return retval;
219 	}
220 }
221 EXPORT_SYMBOL_GPL(w1_triplet);
222 
223 /**
224  * w1_read_8() - Reads 8 bits.
225  * @dev:	the master device
226  *
227  * Return:        the byte read
228  */
w1_read_8(struct w1_master * dev)229 u8 w1_read_8(struct w1_master *dev)
230 {
231 	int i;
232 	u8 res = 0;
233 
234 	if (dev->bus_master->read_byte)
235 		res = dev->bus_master->read_byte(dev->bus_master->data);
236 	else
237 		for (i = 0; i < 8; ++i)
238 			res |= (w1_touch_bit(dev,1) << i);
239 
240 	return res;
241 }
242 EXPORT_SYMBOL_GPL(w1_read_8);
243 
244 /**
245  * w1_write_block() - Writes a series of bytes.
246  * @dev:	the master device
247  * @buf:	pointer to the data to write
248  * @len:	the number of bytes to write
249  */
w1_write_block(struct w1_master * dev,const u8 * buf,int len)250 void w1_write_block(struct w1_master *dev, const u8 *buf, int len)
251 {
252 	int i;
253 
254 	if (dev->bus_master->write_block) {
255 		w1_pre_write(dev);
256 		dev->bus_master->write_block(dev->bus_master->data, buf, len);
257 	}
258 	else
259 		for (i = 0; i < len; ++i)
260 			w1_write_8(dev, buf[i]); /* calls w1_pre_write */
261 	w1_post_write(dev);
262 }
263 EXPORT_SYMBOL_GPL(w1_write_block);
264 
265 /**
266  * w1_touch_block() - Touches a series of bytes.
267  * @dev:	the master device
268  * @buf:	pointer to the data to write
269  * @len:	the number of bytes to write
270  */
w1_touch_block(struct w1_master * dev,u8 * buf,int len)271 void w1_touch_block(struct w1_master *dev, u8 *buf, int len)
272 {
273 	int i, j;
274 	u8 tmp;
275 
276 	for (i = 0; i < len; ++i) {
277 		tmp = 0;
278 		for (j = 0; j < 8; ++j) {
279 			if (j == 7)
280 				w1_pre_write(dev);
281 			tmp |= w1_touch_bit(dev, (buf[i] >> j) & 0x1) << j;
282 		}
283 
284 		buf[i] = tmp;
285 	}
286 }
287 EXPORT_SYMBOL_GPL(w1_touch_block);
288 
289 /**
290  * w1_read_block() - Reads a series of bytes.
291  * @dev:	the master device
292  * @buf:	pointer to the buffer to fill
293  * @len:	the number of bytes to read
294  * Return:	the number of bytes read
295  */
w1_read_block(struct w1_master * dev,u8 * buf,int len)296 u8 w1_read_block(struct w1_master *dev, u8 *buf, int len)
297 {
298 	int i;
299 	u8 ret;
300 
301 	if (dev->bus_master->read_block)
302 		ret = dev->bus_master->read_block(dev->bus_master->data, buf, len);
303 	else {
304 		for (i = 0; i < len; ++i)
305 			buf[i] = w1_read_8(dev);
306 		ret = len;
307 	}
308 
309 	return ret;
310 }
311 EXPORT_SYMBOL_GPL(w1_read_block);
312 
313 /**
314  * w1_reset_bus() - Issues a reset bus sequence.
315  * @dev:	the master device
316  * Return:	0=Device present, 1=No device present or error
317  */
w1_reset_bus(struct w1_master * dev)318 int w1_reset_bus(struct w1_master *dev)
319 {
320 	int result;
321 	unsigned long flags = 0;
322 
323 	if(w1_disable_irqs) local_irq_save(flags);
324 
325 	if (dev->bus_master->reset_bus)
326 		result = dev->bus_master->reset_bus(dev->bus_master->data) & 0x1;
327 	else {
328 		dev->bus_master->write_bit(dev->bus_master->data, 0);
329 		/* minimum 480, max ? us
330 		 * be nice and sleep, except 18b20 spec lists 960us maximum,
331 		 * so until we can sleep with microsecond accuracy, spin.
332 		 * Feel free to come up with some other way to give up the
333 		 * cpu for such a short amount of time AND get it back in
334 		 * the maximum amount of time.
335 		 */
336 		w1_delay(500);
337 		dev->bus_master->write_bit(dev->bus_master->data, 1);
338 		w1_delay(70);
339 
340 		result = dev->bus_master->read_bit(dev->bus_master->data) & 0x1;
341 		/* minimum 70 (above) + 430 = 500 us
342 		 * There aren't any timing requirements between a reset and
343 		 * the following transactions.  Sleeping is safe here.
344 		 */
345 		/* w1_delay(430); min required time */
346 		msleep(1);
347 	}
348 
349 	if(w1_disable_irqs) local_irq_restore(flags);
350 
351 	return result;
352 }
353 EXPORT_SYMBOL_GPL(w1_reset_bus);
354 
w1_calc_crc8(u8 * data,int len)355 u8 w1_calc_crc8(u8 * data, int len)
356 {
357 	u8 crc = 0;
358 
359 	while (len--)
360 		crc = w1_crc8_table[crc ^ *data++];
361 
362 	return crc;
363 }
364 EXPORT_SYMBOL_GPL(w1_calc_crc8);
365 
w1_search_devices(struct w1_master * dev,u8 search_type,w1_slave_found_callback cb)366 void w1_search_devices(struct w1_master *dev, u8 search_type, w1_slave_found_callback cb)
367 {
368 	dev->attempts++;
369 	if (dev->bus_master->search)
370 		dev->bus_master->search(dev->bus_master->data, dev,
371 			search_type, cb);
372 	else
373 		w1_search(dev, search_type, cb);
374 }
375 
376 /**
377  * w1_reset_select_slave() - reset and select a slave
378  * @sl:		the slave to select
379  *
380  * Resets the bus and then selects the slave by sending either a skip rom
381  * or a rom match.  A skip rom is issued if there is only one device
382  * registered on the bus.
383  * The w1 master lock must be held.
384  *
385  * Return:	0=success, anything else=error
386  */
w1_reset_select_slave(struct w1_slave * sl)387 int w1_reset_select_slave(struct w1_slave *sl)
388 {
389 	if (w1_reset_bus(sl->master))
390 		return -1;
391 
392 	if (sl->master->slave_count == 1)
393 		w1_write_8(sl->master, W1_SKIP_ROM);
394 	else {
395 		u8 match[9] = {W1_MATCH_ROM, };
396 		u64 rn = le64_to_cpu(*((u64*)&sl->reg_num));
397 
398 		memcpy(&match[1], &rn, 8);
399 		w1_write_block(sl->master, match, 9);
400 	}
401 	return 0;
402 }
403 EXPORT_SYMBOL_GPL(w1_reset_select_slave);
404 
405 /**
406  * w1_reset_resume_command() - resume instead of another match ROM
407  * @dev:	the master device
408  *
409  * When the workflow with a slave amongst many requires several
410  * successive commands a reset between each, this function is similar
411  * to doing a reset then a match ROM for the last matched ROM. The
412  * advantage being that the matched ROM step is skipped in favor of the
413  * resume command. The slave must support the command of course.
414  *
415  * If the bus has only one slave, traditionnaly the match ROM is skipped
416  * and a "SKIP ROM" is done for efficiency. On multi-slave busses, this
417  * doesn't work of course, but the resume command is the next best thing.
418  *
419  * The w1 master lock must be held.
420  */
w1_reset_resume_command(struct w1_master * dev)421 int w1_reset_resume_command(struct w1_master *dev)
422 {
423 	if (w1_reset_bus(dev))
424 		return -1;
425 
426 	w1_write_8(dev, dev->slave_count > 1 ? W1_RESUME_CMD : W1_SKIP_ROM);
427 	return 0;
428 }
429 EXPORT_SYMBOL_GPL(w1_reset_resume_command);
430 
431 /**
432  * w1_next_pullup() - register for a strong pullup
433  * @dev:	the master device
434  * @delay:	time in milliseconds
435  *
436  * Put out a strong pull-up of the specified duration after the next write
437  * operation.  Not all hardware supports strong pullups.  Hardware that
438  * doesn't support strong pullups will sleep for the given time after the
439  * write operation without a strong pullup.  This is a one shot request for
440  * the next write, specifying zero will clear a previous request.
441  * The w1 master lock must be held.
442  *
443  * Return:	0=success, anything else=error
444  */
w1_next_pullup(struct w1_master * dev,int delay)445 void w1_next_pullup(struct w1_master *dev, int delay)
446 {
447 	dev->pullup_duration = delay;
448 }
449 EXPORT_SYMBOL_GPL(w1_next_pullup);
450