1// SPDX-License-Identifier: GPL-2.0-only
2/**
3 * ds2482.c - provides i2c to w1-master bridge(s)
4 * Copyright (C) 2005  Ben Gardner <bgardner@wabtec.com>
5 *
6 * The DS2482 is a sensor chip made by Dallas Semiconductor (Maxim).
7 * It is a I2C to 1-wire bridge.
8 * There are two variations: -100 and -800, which have 1 or 8 1-wire ports.
9 * The complete datasheet can be obtained from MAXIM's website at:
10 *   http://www.maxim-ic.com/quick_view2.cfm/qv_pk/4382
11 */
12
13#include <linux/module.h>
14#include <linux/init.h>
15#include <linux/slab.h>
16#include <linux/i2c.h>
17#include <linux/delay.h>
18#include <asm/delay.h>
19
20#include <linux/w1.h>
21
22/**
23 * Allow the active pullup to be disabled, default is enabled.
24 *
25 * Note from the DS2482 datasheet:
26 * The APU bit controls whether an active pullup (controlled slew-rate
27 * transistor) or a passive pullup (Rwpu resistor) will be used to drive
28 * a 1-Wire line from low to high. When APU = 0, active pullup is disabled
29 * (resistor mode). Active Pullup should always be selected unless there is
30 * only a single slave on the 1-Wire line.
31 */
32static int ds2482_active_pullup = 1;
33module_param_named(active_pullup, ds2482_active_pullup, int, 0644);
34MODULE_PARM_DESC(active_pullup, "Active pullup (apply to all buses): " \
35				"0-disable, 1-enable (default)");
36
37/* extra configurations - e.g. 1WS */
38static int extra_config;
39module_param(extra_config, int, S_IRUGO | S_IWUSR);
40MODULE_PARM_DESC(extra_config, "Extra Configuration settings 1=APU,2=PPM,3=SPU,8=1WS");
41
42/**
43 * The DS2482 registers - there are 3 registers that are addressed by a read
44 * pointer. The read pointer is set by the last command executed.
45 *
46 * To read the data, issue a register read for any address
47 */
48#define DS2482_CMD_RESET		0xF0	/* No param */
49#define DS2482_CMD_SET_READ_PTR		0xE1	/* Param: DS2482_PTR_CODE_xxx */
50#define DS2482_CMD_CHANNEL_SELECT	0xC3	/* Param: Channel byte - DS2482-800 only */
51#define DS2482_CMD_WRITE_CONFIG		0xD2	/* Param: Config byte */
52#define DS2482_CMD_1WIRE_RESET		0xB4	/* Param: None */
53#define DS2482_CMD_1WIRE_SINGLE_BIT	0x87	/* Param: Bit byte (bit7) */
54#define DS2482_CMD_1WIRE_WRITE_BYTE	0xA5	/* Param: Data byte */
55#define DS2482_CMD_1WIRE_READ_BYTE	0x96	/* Param: None */
56/* Note to read the byte, Set the ReadPtr to Data then read (any addr) */
57#define DS2482_CMD_1WIRE_TRIPLET	0x78	/* Param: Dir byte (bit7) */
58
59/* Values for DS2482_CMD_SET_READ_PTR */
60#define DS2482_PTR_CODE_STATUS		0xF0
61#define DS2482_PTR_CODE_DATA		0xE1
62#define DS2482_PTR_CODE_CHANNEL		0xD2	/* DS2482-800 only */
63#define DS2482_PTR_CODE_CONFIG		0xC3
64
65/**
66 * Configure Register bit definitions
67 * The top 4 bits always read 0.
68 * To write, the top nibble must be the 1's compl. of the low nibble.
69 */
70#define DS2482_REG_CFG_1WS		0x08	/* 1-wire speed */
71#define DS2482_REG_CFG_SPU		0x04	/* strong pull-up */
72#define DS2482_REG_CFG_PPM		0x02	/* presence pulse masking */
73#define DS2482_REG_CFG_APU		0x01	/* active pull-up */
74
75
76/**
77 * Write and verify codes for the CHANNEL_SELECT command (DS2482-800 only).
78 * To set the channel, write the value at the index of the channel.
79 * Read and compare against the corresponding value to verify the change.
80 */
81static const u8 ds2482_chan_wr[8] =
82	{ 0xF0, 0xE1, 0xD2, 0xC3, 0xB4, 0xA5, 0x96, 0x87 };
83static const u8 ds2482_chan_rd[8] =
84	{ 0xB8, 0xB1, 0xAA, 0xA3, 0x9C, 0x95, 0x8E, 0x87 };
85
86
87/**
88 * Status Register bit definitions (read only)
89 */
90#define DS2482_REG_STS_DIR		0x80
91#define DS2482_REG_STS_TSB		0x40
92#define DS2482_REG_STS_SBR		0x20
93#define DS2482_REG_STS_RST		0x10
94#define DS2482_REG_STS_LL		0x08
95#define DS2482_REG_STS_SD		0x04
96#define DS2482_REG_STS_PPD		0x02
97#define DS2482_REG_STS_1WB		0x01
98
99/*
100 * Client data (each client gets its own)
101 */
102
103struct ds2482_data;
104
105struct ds2482_w1_chan {
106	struct ds2482_data	*pdev;
107	u8			channel;
108	struct w1_bus_master	w1_bm;
109};
110
111struct ds2482_data {
112	struct i2c_client	*client;
113	struct mutex		access_lock;
114
115	/* 1-wire interface(s) */
116	int			w1_count;	/* 1 or 8 */
117	struct ds2482_w1_chan	w1_ch[8];
118
119	/* per-device values */
120	u8			channel;
121	u8			read_prt;	/* see DS2482_PTR_CODE_xxx */
122	u8			reg_config;
123};
124
125
126/**
127 * Helper to calculate values for configuration register
128 * @param conf the raw config value
129 * @return the value w/ complements that can be written to register
130 */
131static inline u8 ds2482_calculate_config(u8 conf)
132{
133	conf |= extra_config;
134
135	if (ds2482_active_pullup)
136		conf |= DS2482_REG_CFG_APU;
137
138	return conf | ((~conf & 0x0f) << 4);
139}
140
141
142/**
143 * Sets the read pointer.
144 * @param pdev		The ds2482 client pointer
145 * @param read_ptr	see DS2482_PTR_CODE_xxx above
146 * @return -1 on failure, 0 on success
147 */
148static inline int ds2482_select_register(struct ds2482_data *pdev, u8 read_ptr)
149{
150	if (pdev->read_prt != read_ptr) {
151		if (i2c_smbus_write_byte_data(pdev->client,
152					      DS2482_CMD_SET_READ_PTR,
153					      read_ptr) < 0)
154			return -1;
155
156		pdev->read_prt = read_ptr;
157	}
158	return 0;
159}
160
161/**
162 * Sends a command without a parameter
163 * @param pdev	The ds2482 client pointer
164 * @param cmd	DS2482_CMD_RESET,
165 *		DS2482_CMD_1WIRE_RESET,
166 *		DS2482_CMD_1WIRE_READ_BYTE
167 * @return -1 on failure, 0 on success
168 */
169static inline int ds2482_send_cmd(struct ds2482_data *pdev, u8 cmd)
170{
171	if (i2c_smbus_write_byte(pdev->client, cmd) < 0)
172		return -1;
173
174	pdev->read_prt = DS2482_PTR_CODE_STATUS;
175	return 0;
176}
177
178/**
179 * Sends a command with a parameter
180 * @param pdev	The ds2482 client pointer
181 * @param cmd	DS2482_CMD_WRITE_CONFIG,
182 *		DS2482_CMD_1WIRE_SINGLE_BIT,
183 *		DS2482_CMD_1WIRE_WRITE_BYTE,
184 *		DS2482_CMD_1WIRE_TRIPLET
185 * @param byte	The data to send
186 * @return -1 on failure, 0 on success
187 */
188static inline int ds2482_send_cmd_data(struct ds2482_data *pdev,
189				       u8 cmd, u8 byte)
190{
191	if (i2c_smbus_write_byte_data(pdev->client, cmd, byte) < 0)
192		return -1;
193
194	/* all cmds leave in STATUS, except CONFIG */
195	pdev->read_prt = (cmd != DS2482_CMD_WRITE_CONFIG) ?
196			 DS2482_PTR_CODE_STATUS : DS2482_PTR_CODE_CONFIG;
197	return 0;
198}
199
200
201/*
202 * 1-Wire interface code
203 */
204
205#define DS2482_WAIT_IDLE_TIMEOUT	100
206
207/**
208 * Waits until the 1-wire interface is idle (not busy)
209 *
210 * @param pdev Pointer to the device structure
211 * @return the last value read from status or -1 (failure)
212 */
213static int ds2482_wait_1wire_idle(struct ds2482_data *pdev)
214{
215	int temp = -1;
216	int retries = 0;
217
218	if (!ds2482_select_register(pdev, DS2482_PTR_CODE_STATUS)) {
219		do {
220			temp = i2c_smbus_read_byte(pdev->client);
221		} while ((temp >= 0) && (temp & DS2482_REG_STS_1WB) &&
222			 (++retries < DS2482_WAIT_IDLE_TIMEOUT));
223	}
224
225	if (retries >= DS2482_WAIT_IDLE_TIMEOUT)
226		pr_err("%s: timeout on channel %d\n",
227		       __func__, pdev->channel);
228
229	return temp;
230}
231
232/**
233 * Selects a w1 channel.
234 * The 1-wire interface must be idle before calling this function.
235 *
236 * @param pdev		The ds2482 client pointer
237 * @param channel	0-7
238 * @return		-1 (failure) or 0 (success)
239 */
240static int ds2482_set_channel(struct ds2482_data *pdev, u8 channel)
241{
242	if (i2c_smbus_write_byte_data(pdev->client, DS2482_CMD_CHANNEL_SELECT,
243				      ds2482_chan_wr[channel]) < 0)
244		return -1;
245
246	pdev->read_prt = DS2482_PTR_CODE_CHANNEL;
247	pdev->channel = -1;
248	if (i2c_smbus_read_byte(pdev->client) == ds2482_chan_rd[channel]) {
249		pdev->channel = channel;
250		return 0;
251	}
252	return -1;
253}
254
255
256/**
257 * Performs the touch-bit function, which writes a 0 or 1 and reads the level.
258 *
259 * @param data	The ds2482 channel pointer
260 * @param bit	The level to write: 0 or non-zero
261 * @return	The level read: 0 or 1
262 */
263static u8 ds2482_w1_touch_bit(void *data, u8 bit)
264{
265	struct ds2482_w1_chan *pchan = data;
266	struct ds2482_data    *pdev = pchan->pdev;
267	int status = -1;
268
269	mutex_lock(&pdev->access_lock);
270
271	/* Select the channel */
272	ds2482_wait_1wire_idle(pdev);
273	if (pdev->w1_count > 1)
274		ds2482_set_channel(pdev, pchan->channel);
275
276	/* Send the touch command, wait until 1WB == 0, return the status */
277	if (!ds2482_send_cmd_data(pdev, DS2482_CMD_1WIRE_SINGLE_BIT,
278				  bit ? 0xFF : 0))
279		status = ds2482_wait_1wire_idle(pdev);
280
281	mutex_unlock(&pdev->access_lock);
282
283	return (status & DS2482_REG_STS_SBR) ? 1 : 0;
284}
285
286/**
287 * Performs the triplet function, which reads two bits and writes a bit.
288 * The bit written is determined by the two reads:
289 *   00 => dbit, 01 => 0, 10 => 1
290 *
291 * @param data	The ds2482 channel pointer
292 * @param dbit	The direction to choose if both branches are valid
293 * @return	b0=read1 b1=read2 b3=bit written
294 */
295static u8 ds2482_w1_triplet(void *data, u8 dbit)
296{
297	struct ds2482_w1_chan *pchan = data;
298	struct ds2482_data    *pdev = pchan->pdev;
299	int status = (3 << 5);
300
301	mutex_lock(&pdev->access_lock);
302
303	/* Select the channel */
304	ds2482_wait_1wire_idle(pdev);
305	if (pdev->w1_count > 1)
306		ds2482_set_channel(pdev, pchan->channel);
307
308	/* Send the triplet command, wait until 1WB == 0, return the status */
309	if (!ds2482_send_cmd_data(pdev, DS2482_CMD_1WIRE_TRIPLET,
310				  dbit ? 0xFF : 0))
311		status = ds2482_wait_1wire_idle(pdev);
312
313	mutex_unlock(&pdev->access_lock);
314
315	/* Decode the status */
316	return (status >> 5);
317}
318
319/**
320 * Performs the write byte function.
321 *
322 * @param data	The ds2482 channel pointer
323 * @param byte	The value to write
324 */
325static void ds2482_w1_write_byte(void *data, u8 byte)
326{
327	struct ds2482_w1_chan *pchan = data;
328	struct ds2482_data    *pdev = pchan->pdev;
329
330	mutex_lock(&pdev->access_lock);
331
332	/* Select the channel */
333	ds2482_wait_1wire_idle(pdev);
334	if (pdev->w1_count > 1)
335		ds2482_set_channel(pdev, pchan->channel);
336
337	/* Send the write byte command */
338	ds2482_send_cmd_data(pdev, DS2482_CMD_1WIRE_WRITE_BYTE, byte);
339
340	mutex_unlock(&pdev->access_lock);
341}
342
343/**
344 * Performs the read byte function.
345 *
346 * @param data	The ds2482 channel pointer
347 * @return	The value read
348 */
349static u8 ds2482_w1_read_byte(void *data)
350{
351	struct ds2482_w1_chan *pchan = data;
352	struct ds2482_data    *pdev = pchan->pdev;
353	int result;
354
355	mutex_lock(&pdev->access_lock);
356
357	/* Select the channel */
358	ds2482_wait_1wire_idle(pdev);
359	if (pdev->w1_count > 1)
360		ds2482_set_channel(pdev, pchan->channel);
361
362	/* Send the read byte command */
363	ds2482_send_cmd(pdev, DS2482_CMD_1WIRE_READ_BYTE);
364
365	/* Wait until 1WB == 0 */
366	ds2482_wait_1wire_idle(pdev);
367
368	/* Select the data register */
369	ds2482_select_register(pdev, DS2482_PTR_CODE_DATA);
370
371	/* Read the data byte */
372	result = i2c_smbus_read_byte(pdev->client);
373
374	mutex_unlock(&pdev->access_lock);
375
376	return result;
377}
378
379
380/**
381 * Sends a reset on the 1-wire interface
382 *
383 * @param data	The ds2482 channel pointer
384 * @return	0=Device present, 1=No device present or error
385 */
386static u8 ds2482_w1_reset_bus(void *data)
387{
388	struct ds2482_w1_chan *pchan = data;
389	struct ds2482_data    *pdev = pchan->pdev;
390	int err;
391	u8 retval = 1;
392
393	mutex_lock(&pdev->access_lock);
394
395	/* Select the channel */
396	ds2482_wait_1wire_idle(pdev);
397	if (pdev->w1_count > 1)
398		ds2482_set_channel(pdev, pchan->channel);
399
400	/* Send the reset command */
401	err = ds2482_send_cmd(pdev, DS2482_CMD_1WIRE_RESET);
402	if (err >= 0) {
403		/* Wait until the reset is complete */
404		err = ds2482_wait_1wire_idle(pdev);
405		retval = !(err & DS2482_REG_STS_PPD);
406
407		/* If the chip did reset since detect, re-config it */
408		if (err & DS2482_REG_STS_RST)
409			ds2482_send_cmd_data(pdev, DS2482_CMD_WRITE_CONFIG,
410					     ds2482_calculate_config(0x00));
411	}
412
413	mutex_unlock(&pdev->access_lock);
414
415	return retval;
416}
417
418static u8 ds2482_w1_set_pullup(void *data, int delay)
419{
420	struct ds2482_w1_chan *pchan = data;
421	struct ds2482_data    *pdev = pchan->pdev;
422	u8 retval = 1;
423
424	/* if delay is non-zero activate the pullup,
425	 * the strong pullup will be automatically deactivated
426	 * by the master, so do not explicitly deactive it
427	 */
428	if (delay) {
429		/* both waits are crucial, otherwise devices might not be
430		 * powered long enough, causing e.g. a w1_therm sensor to
431		 * provide wrong conversion results
432		 */
433		ds2482_wait_1wire_idle(pdev);
434		/* note: it seems like both SPU and APU have to be set! */
435		retval = ds2482_send_cmd_data(pdev, DS2482_CMD_WRITE_CONFIG,
436			ds2482_calculate_config(DS2482_REG_CFG_SPU |
437						DS2482_REG_CFG_APU));
438		ds2482_wait_1wire_idle(pdev);
439	}
440
441	return retval;
442}
443
444
445static int ds2482_probe(struct i2c_client *client,
446			const struct i2c_device_id *id)
447{
448	struct ds2482_data *data;
449	int err = -ENODEV;
450	int temp1;
451	int idx;
452
453	if (!i2c_check_functionality(client->adapter,
454				     I2C_FUNC_SMBUS_WRITE_BYTE_DATA |
455				     I2C_FUNC_SMBUS_BYTE))
456		return -ENODEV;
457
458	if (!(data = kzalloc(sizeof(struct ds2482_data), GFP_KERNEL))) {
459		err = -ENOMEM;
460		goto exit;
461	}
462
463	data->client = client;
464	i2c_set_clientdata(client, data);
465
466	/* Reset the device (sets the read_ptr to status) */
467	if (ds2482_send_cmd(data, DS2482_CMD_RESET) < 0) {
468		dev_warn(&client->dev, "DS2482 reset failed.\n");
469		goto exit_free;
470	}
471
472	/* Sleep at least 525ns to allow the reset to complete */
473	ndelay(525);
474
475	/* Read the status byte - only reset bit and line should be set */
476	temp1 = i2c_smbus_read_byte(client);
477	if (temp1 != (DS2482_REG_STS_LL | DS2482_REG_STS_RST)) {
478		dev_warn(&client->dev, "DS2482 reset status "
479			 "0x%02X - not a DS2482\n", temp1);
480		goto exit_free;
481	}
482
483	/* Detect the 8-port version */
484	data->w1_count = 1;
485	if (ds2482_set_channel(data, 7) == 0)
486		data->w1_count = 8;
487
488	/* Set all config items to 0 (off) */
489	ds2482_send_cmd_data(data, DS2482_CMD_WRITE_CONFIG,
490		ds2482_calculate_config(0x00));
491
492	mutex_init(&data->access_lock);
493
494	/* Register 1-wire interface(s) */
495	for (idx = 0; idx < data->w1_count; idx++) {
496		data->w1_ch[idx].pdev = data;
497		data->w1_ch[idx].channel = idx;
498
499		/* Populate all the w1 bus master stuff */
500		data->w1_ch[idx].w1_bm.data       = &data->w1_ch[idx];
501		data->w1_ch[idx].w1_bm.read_byte  = ds2482_w1_read_byte;
502		data->w1_ch[idx].w1_bm.write_byte = ds2482_w1_write_byte;
503		data->w1_ch[idx].w1_bm.touch_bit  = ds2482_w1_touch_bit;
504		data->w1_ch[idx].w1_bm.triplet    = ds2482_w1_triplet;
505		data->w1_ch[idx].w1_bm.reset_bus  = ds2482_w1_reset_bus;
506		data->w1_ch[idx].w1_bm.set_pullup = ds2482_w1_set_pullup;
507
508		err = w1_add_master_device(&data->w1_ch[idx].w1_bm);
509		if (err) {
510			data->w1_ch[idx].pdev = NULL;
511			goto exit_w1_remove;
512		}
513	}
514
515	return 0;
516
517exit_w1_remove:
518	for (idx = 0; idx < data->w1_count; idx++) {
519		if (data->w1_ch[idx].pdev != NULL)
520			w1_remove_master_device(&data->w1_ch[idx].w1_bm);
521	}
522exit_free:
523	kfree(data);
524exit:
525	return err;
526}
527
528static int ds2482_remove(struct i2c_client *client)
529{
530	struct ds2482_data   *data = i2c_get_clientdata(client);
531	int idx;
532
533	/* Unregister the 1-wire bridge(s) */
534	for (idx = 0; idx < data->w1_count; idx++) {
535		if (data->w1_ch[idx].pdev != NULL)
536			w1_remove_master_device(&data->w1_ch[idx].w1_bm);
537	}
538
539	/* Free the memory */
540	kfree(data);
541	return 0;
542}
543
544/**
545 * Driver data (common to all clients)
546 */
547static const struct i2c_device_id ds2482_id[] = {
548	{ "ds2482", 0 },
549	{ }
550};
551MODULE_DEVICE_TABLE(i2c, ds2482_id);
552
553static struct i2c_driver ds2482_driver = {
554	.driver = {
555		.name	= "ds2482",
556	},
557	.probe		= ds2482_probe,
558	.remove		= ds2482_remove,
559	.id_table	= ds2482_id,
560};
561module_i2c_driver(ds2482_driver);
562
563MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>");
564MODULE_DESCRIPTION("DS2482 driver");
565
566MODULE_LICENSE("GPL");
567