1 /*
2  * ntc_thermistor.c - NTC Thermistors
3  *
4  *  Copyright (C) 2010 Samsung Electronics
5  *  MyungJoo Ham <myungjoo.ham@samsung.com>
6  *
7  * This program is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License as published by
9  * the Free Software Foundation; either version 2 of the License, or
10  * (at your option) any later version.
11  *
12  * This program is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15  * GNU General Public License for more details.
16  *
17  * You should have received a copy of the GNU General Public License
18  * along with this program; if not, write to the Free Software
19  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
20  *
21  */
22 
23 #include <linux/slab.h>
24 #include <linux/module.h>
25 #include <linux/pm_runtime.h>
26 #include <linux/math64.h>
27 #include <linux/platform_device.h>
28 #include <linux/err.h>
29 #include <linux/of.h>
30 #include <linux/of_device.h>
31 
32 #include <linux/platform_data/ntc_thermistor.h>
33 
34 #include <linux/iio/iio.h>
35 #include <linux/iio/machine.h>
36 #include <linux/iio/driver.h>
37 #include <linux/iio/consumer.h>
38 
39 #include <linux/hwmon.h>
40 #include <linux/hwmon-sysfs.h>
41 #include <linux/thermal.h>
42 
43 struct ntc_compensation {
44 	int		temp_c;
45 	unsigned int	ohm;
46 };
47 
48 /* Order matters, ntc_match references the entries by index */
49 static const struct platform_device_id ntc_thermistor_id[] = {
50 	{ "ncp15wb473", TYPE_NCPXXWB473 },
51 	{ "ncp18wb473", TYPE_NCPXXWB473 },
52 	{ "ncp21wb473", TYPE_NCPXXWB473 },
53 	{ "ncp03wb473", TYPE_NCPXXWB473 },
54 	{ "ncp15wl333", TYPE_NCPXXWL333 },
55 	{ "b57330v2103", TYPE_B57330V2103},
56 	{ "ncp03wf104", TYPE_NCPXXWF104 },
57 	{ },
58 };
59 
60 /*
61  * A compensation table should be sorted by the values of .ohm
62  * in descending order.
63  * The following compensation tables are from the specification of Murata NTC
64  * Thermistors Datasheet
65  */
66 static const struct ntc_compensation ncpXXwb473[] = {
67 	{ .temp_c	= -40, .ohm	= 1747920 },
68 	{ .temp_c	= -35, .ohm	= 1245428 },
69 	{ .temp_c	= -30, .ohm	= 898485 },
70 	{ .temp_c	= -25, .ohm	= 655802 },
71 	{ .temp_c	= -20, .ohm	= 483954 },
72 	{ .temp_c	= -15, .ohm	= 360850 },
73 	{ .temp_c	= -10, .ohm	= 271697 },
74 	{ .temp_c	= -5, .ohm	= 206463 },
75 	{ .temp_c	= 0, .ohm	= 158214 },
76 	{ .temp_c	= 5, .ohm	= 122259 },
77 	{ .temp_c	= 10, .ohm	= 95227 },
78 	{ .temp_c	= 15, .ohm	= 74730 },
79 	{ .temp_c	= 20, .ohm	= 59065 },
80 	{ .temp_c	= 25, .ohm	= 47000 },
81 	{ .temp_c	= 30, .ohm	= 37643 },
82 	{ .temp_c	= 35, .ohm	= 30334 },
83 	{ .temp_c	= 40, .ohm	= 24591 },
84 	{ .temp_c	= 45, .ohm	= 20048 },
85 	{ .temp_c	= 50, .ohm	= 16433 },
86 	{ .temp_c	= 55, .ohm	= 13539 },
87 	{ .temp_c	= 60, .ohm	= 11209 },
88 	{ .temp_c	= 65, .ohm	= 9328 },
89 	{ .temp_c	= 70, .ohm	= 7798 },
90 	{ .temp_c	= 75, .ohm	= 6544 },
91 	{ .temp_c	= 80, .ohm	= 5518 },
92 	{ .temp_c	= 85, .ohm	= 4674 },
93 	{ .temp_c	= 90, .ohm	= 3972 },
94 	{ .temp_c	= 95, .ohm	= 3388 },
95 	{ .temp_c	= 100, .ohm	= 2902 },
96 	{ .temp_c	= 105, .ohm	= 2494 },
97 	{ .temp_c	= 110, .ohm	= 2150 },
98 	{ .temp_c	= 115, .ohm	= 1860 },
99 	{ .temp_c	= 120, .ohm	= 1615 },
100 	{ .temp_c	= 125, .ohm	= 1406 },
101 };
102 static const struct ntc_compensation ncpXXwl333[] = {
103 	{ .temp_c	= -40, .ohm	= 1610154 },
104 	{ .temp_c	= -35, .ohm	= 1130850 },
105 	{ .temp_c	= -30, .ohm	= 802609 },
106 	{ .temp_c	= -25, .ohm	= 575385 },
107 	{ .temp_c	= -20, .ohm	= 416464 },
108 	{ .temp_c	= -15, .ohm	= 304219 },
109 	{ .temp_c	= -10, .ohm	= 224193 },
110 	{ .temp_c	= -5, .ohm	= 166623 },
111 	{ .temp_c	= 0, .ohm	= 124850 },
112 	{ .temp_c	= 5, .ohm	= 94287 },
113 	{ .temp_c	= 10, .ohm	= 71747 },
114 	{ .temp_c	= 15, .ohm	= 54996 },
115 	{ .temp_c	= 20, .ohm	= 42455 },
116 	{ .temp_c	= 25, .ohm	= 33000 },
117 	{ .temp_c	= 30, .ohm	= 25822 },
118 	{ .temp_c	= 35, .ohm	= 20335 },
119 	{ .temp_c	= 40, .ohm	= 16115 },
120 	{ .temp_c	= 45, .ohm	= 12849 },
121 	{ .temp_c	= 50, .ohm	= 10306 },
122 	{ .temp_c	= 55, .ohm	= 8314 },
123 	{ .temp_c	= 60, .ohm	= 6746 },
124 	{ .temp_c	= 65, .ohm	= 5503 },
125 	{ .temp_c	= 70, .ohm	= 4513 },
126 	{ .temp_c	= 75, .ohm	= 3721 },
127 	{ .temp_c	= 80, .ohm	= 3084 },
128 	{ .temp_c	= 85, .ohm	= 2569 },
129 	{ .temp_c	= 90, .ohm	= 2151 },
130 	{ .temp_c	= 95, .ohm	= 1809 },
131 	{ .temp_c	= 100, .ohm	= 1529 },
132 	{ .temp_c	= 105, .ohm	= 1299 },
133 	{ .temp_c	= 110, .ohm	= 1108 },
134 	{ .temp_c	= 115, .ohm	= 949 },
135 	{ .temp_c	= 120, .ohm	= 817 },
136 	{ .temp_c	= 125, .ohm	= 707 },
137 };
138 
139 static const struct ntc_compensation ncpXXwf104[] = {
140 	{ .temp_c	= -40, .ohm	= 4397119 },
141 	{ .temp_c	= -35, .ohm	= 3088599 },
142 	{ .temp_c	= -30, .ohm	= 2197225 },
143 	{ .temp_c	= -25, .ohm	= 1581881 },
144 	{ .temp_c	= -20, .ohm	= 1151037 },
145 	{ .temp_c	= -15, .ohm	= 846579 },
146 	{ .temp_c	= -10, .ohm	= 628988 },
147 	{ .temp_c	= -5, .ohm	= 471632 },
148 	{ .temp_c	= 0, .ohm	= 357012 },
149 	{ .temp_c	= 5, .ohm	= 272500 },
150 	{ .temp_c	= 10, .ohm	= 209710 },
151 	{ .temp_c	= 15, .ohm	= 162651 },
152 	{ .temp_c	= 20, .ohm	= 127080 },
153 	{ .temp_c	= 25, .ohm	= 100000 },
154 	{ .temp_c	= 30, .ohm	= 79222 },
155 	{ .temp_c	= 35, .ohm	= 63167 },
156 	{ .temp_c	= 40, .ohm	= 50677 },
157 	{ .temp_c	= 45, .ohm	= 40904 },
158 	{ .temp_c	= 50, .ohm	= 33195 },
159 	{ .temp_c	= 55, .ohm	= 27091 },
160 	{ .temp_c	= 60, .ohm	= 22224 },
161 	{ .temp_c	= 65, .ohm	= 18323 },
162 	{ .temp_c	= 70, .ohm	= 15184 },
163 	{ .temp_c	= 75, .ohm	= 12635 },
164 	{ .temp_c	= 80, .ohm	= 10566 },
165 	{ .temp_c	= 85, .ohm	= 8873 },
166 	{ .temp_c	= 90, .ohm	= 7481 },
167 	{ .temp_c	= 95, .ohm	= 6337 },
168 	{ .temp_c	= 100, .ohm	= 5384 },
169 	{ .temp_c	= 105, .ohm	= 4594 },
170 	{ .temp_c	= 110, .ohm	= 3934 },
171 	{ .temp_c	= 115, .ohm	= 3380 },
172 	{ .temp_c	= 120, .ohm	= 2916 },
173 	{ .temp_c	= 125, .ohm	= 2522 },
174 };
175 
176 /*
177  * The following compensation table is from the specification of EPCOS NTC
178  * Thermistors Datasheet
179  */
180 static const struct ntc_compensation b57330v2103[] = {
181 	{ .temp_c	= -40, .ohm	= 190030 },
182 	{ .temp_c	= -35, .ohm	= 145360 },
183 	{ .temp_c	= -30, .ohm	= 112060 },
184 	{ .temp_c	= -25, .ohm	= 87041 },
185 	{ .temp_c	= -20, .ohm	= 68104 },
186 	{ .temp_c	= -15, .ohm	= 53665 },
187 	{ .temp_c	= -10, .ohm	= 42576 },
188 	{ .temp_c	= -5, .ohm	= 34001 },
189 	{ .temp_c	= 0, .ohm	= 27326 },
190 	{ .temp_c	= 5, .ohm	= 22096 },
191 	{ .temp_c	= 10, .ohm	= 17973 },
192 	{ .temp_c	= 15, .ohm	= 14703 },
193 	{ .temp_c	= 20, .ohm	= 12090 },
194 	{ .temp_c	= 25, .ohm	= 10000 },
195 	{ .temp_c	= 30, .ohm	= 8311 },
196 	{ .temp_c	= 35, .ohm	= 6941 },
197 	{ .temp_c	= 40, .ohm	= 5825 },
198 	{ .temp_c	= 45, .ohm	= 4911 },
199 	{ .temp_c	= 50, .ohm	= 4158 },
200 	{ .temp_c	= 55, .ohm	= 3536 },
201 	{ .temp_c	= 60, .ohm	= 3019 },
202 	{ .temp_c	= 65, .ohm	= 2588 },
203 	{ .temp_c	= 70, .ohm	= 2227 },
204 	{ .temp_c	= 75, .ohm	= 1924 },
205 	{ .temp_c	= 80, .ohm	= 1668 },
206 	{ .temp_c	= 85, .ohm	= 1451 },
207 	{ .temp_c	= 90, .ohm	= 1266 },
208 	{ .temp_c	= 95, .ohm	= 1108 },
209 	{ .temp_c	= 100, .ohm	= 973 },
210 	{ .temp_c	= 105, .ohm	= 857 },
211 	{ .temp_c	= 110, .ohm	= 757 },
212 	{ .temp_c	= 115, .ohm	= 671 },
213 	{ .temp_c	= 120, .ohm	= 596 },
214 	{ .temp_c	= 125, .ohm	= 531 },
215 };
216 
217 struct ntc_data {
218 	struct device *hwmon_dev;
219 	struct ntc_thermistor_platform_data *pdata;
220 	const struct ntc_compensation *comp;
221 	struct device *dev;
222 	int n_comp;
223 	char name[PLATFORM_NAME_SIZE];
224 	struct thermal_zone_device *tz;
225 };
226 
227 #if defined(CONFIG_OF) && IS_ENABLED(CONFIG_IIO)
228 static int ntc_adc_iio_read(struct ntc_thermistor_platform_data *pdata)
229 {
230 	struct iio_channel *channel = pdata->chan;
231 	int raw, uv, ret;
232 
233 	ret = iio_read_channel_raw(channel, &raw);
234 	if (ret < 0) {
235 		pr_err("read channel() error: %d\n", ret);
236 		return ret;
237 	}
238 
239 	ret = iio_convert_raw_to_processed(channel, raw, &uv, 1000);
240 	if (ret < 0) {
241 		/* Assume 12 bit ADC with vref at pullup_uv */
242 		uv = (pdata->pullup_uv * (s64)raw) >> 12;
243 	}
244 
245 	return uv;
246 }
247 
248 static const struct of_device_id ntc_match[] = {
249 	{ .compatible = "murata,ncp15wb473",
250 		.data = &ntc_thermistor_id[0] },
251 	{ .compatible = "murata,ncp18wb473",
252 		.data = &ntc_thermistor_id[1] },
253 	{ .compatible = "murata,ncp21wb473",
254 		.data = &ntc_thermistor_id[2] },
255 	{ .compatible = "murata,ncp03wb473",
256 		.data = &ntc_thermistor_id[3] },
257 	{ .compatible = "murata,ncp15wl333",
258 		.data = &ntc_thermistor_id[4] },
259 	{ .compatible = "epcos,b57330v2103",
260 		.data = &ntc_thermistor_id[5]},
261 	{ .compatible = "murata,ncp03wf104",
262 		.data = &ntc_thermistor_id[6] },
263 
264 	/* Usage of vendor name "ntc" is deprecated */
265 	{ .compatible = "ntc,ncp15wb473",
266 		.data = &ntc_thermistor_id[0] },
267 	{ .compatible = "ntc,ncp18wb473",
268 		.data = &ntc_thermistor_id[1] },
269 	{ .compatible = "ntc,ncp21wb473",
270 		.data = &ntc_thermistor_id[2] },
271 	{ .compatible = "ntc,ncp03wb473",
272 		.data = &ntc_thermistor_id[3] },
273 	{ .compatible = "ntc,ncp15wl333",
274 		.data = &ntc_thermistor_id[4] },
275 	{ },
276 };
277 MODULE_DEVICE_TABLE(of, ntc_match);
278 
279 static struct ntc_thermistor_platform_data *
280 ntc_thermistor_parse_dt(struct platform_device *pdev)
281 {
282 	struct iio_channel *chan;
283 	enum iio_chan_type type;
284 	struct device_node *np = pdev->dev.of_node;
285 	struct ntc_thermistor_platform_data *pdata;
286 	int ret;
287 
288 	if (!np)
289 		return NULL;
290 
291 	pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
292 	if (!pdata)
293 		return ERR_PTR(-ENOMEM);
294 
295 	chan = iio_channel_get(&pdev->dev, NULL);
296 	if (IS_ERR(chan))
297 		return ERR_CAST(chan);
298 
299 	ret = iio_get_channel_type(chan, &type);
300 	if (ret < 0)
301 		return ERR_PTR(ret);
302 
303 	if (type != IIO_VOLTAGE)
304 		return ERR_PTR(-EINVAL);
305 
306 	if (of_property_read_u32(np, "pullup-uv", &pdata->pullup_uv))
307 		return ERR_PTR(-ENODEV);
308 	if (of_property_read_u32(np, "pullup-ohm", &pdata->pullup_ohm))
309 		return ERR_PTR(-ENODEV);
310 	if (of_property_read_u32(np, "pulldown-ohm", &pdata->pulldown_ohm))
311 		return ERR_PTR(-ENODEV);
312 
313 	if (of_find_property(np, "connected-positive", NULL))
314 		pdata->connect = NTC_CONNECTED_POSITIVE;
315 	else /* status change should be possible if not always on. */
316 		pdata->connect = NTC_CONNECTED_GROUND;
317 
318 	pdata->chan = chan;
319 	pdata->read_uv = ntc_adc_iio_read;
320 
321 	return pdata;
322 }
323 static void ntc_iio_channel_release(struct ntc_thermistor_platform_data *pdata)
324 {
325 	if (pdata->chan)
326 		iio_channel_release(pdata->chan);
327 }
328 #else
329 static struct ntc_thermistor_platform_data *
330 ntc_thermistor_parse_dt(struct platform_device *pdev)
331 {
332 	return NULL;
333 }
334 
335 #define ntc_match	NULL
336 
337 static void ntc_iio_channel_release(struct ntc_thermistor_platform_data *pdata)
338 { }
339 #endif
340 
341 static inline u64 div64_u64_safe(u64 dividend, u64 divisor)
342 {
343 	if (divisor == 0 && dividend == 0)
344 		return 0;
345 	if (divisor == 0)
346 		return UINT_MAX;
347 	return div64_u64(dividend, divisor);
348 }
349 
350 static int get_ohm_of_thermistor(struct ntc_data *data, unsigned int uv)
351 {
352 	struct ntc_thermistor_platform_data *pdata = data->pdata;
353 	u32 puv = pdata->pullup_uv;
354 	u64 n, puo, pdo;
355 	puo = pdata->pullup_ohm;
356 	pdo = pdata->pulldown_ohm;
357 
358 	if (uv == 0)
359 		return (pdata->connect == NTC_CONNECTED_POSITIVE) ?
360 			INT_MAX : 0;
361 	if (uv >= puv)
362 		return (pdata->connect == NTC_CONNECTED_POSITIVE) ?
363 			0 : INT_MAX;
364 
365 	if (pdata->connect == NTC_CONNECTED_POSITIVE && puo == 0)
366 		n = div_u64(pdo * (puv - uv), uv);
367 	else if (pdata->connect == NTC_CONNECTED_GROUND && pdo == 0)
368 		n = div_u64(puo * uv, puv - uv);
369 	else if (pdata->connect == NTC_CONNECTED_POSITIVE)
370 		n = div64_u64_safe(pdo * puo * (puv - uv),
371 				puo * uv - pdo * (puv - uv));
372 	else
373 		n = div64_u64_safe(pdo * puo * uv, pdo * (puv - uv) - puo * uv);
374 
375 	if (n > INT_MAX)
376 		n = INT_MAX;
377 	return n;
378 }
379 
380 static void lookup_comp(struct ntc_data *data, unsigned int ohm,
381 			int *i_low, int *i_high)
382 {
383 	int start, end, mid;
384 
385 	/*
386 	 * Handle special cases: Resistance is higher than or equal to
387 	 * resistance in first table entry, or resistance is lower or equal
388 	 * to resistance in last table entry.
389 	 * In these cases, return i_low == i_high, either pointing to the
390 	 * beginning or to the end of the table depending on the condition.
391 	 */
392 	if (ohm >= data->comp[0].ohm) {
393 		*i_low = 0;
394 		*i_high = 0;
395 		return;
396 	}
397 	if (ohm <= data->comp[data->n_comp - 1].ohm) {
398 		*i_low = data->n_comp - 1;
399 		*i_high = data->n_comp - 1;
400 		return;
401 	}
402 
403 	/* Do a binary search on compensation table */
404 	start = 0;
405 	end = data->n_comp;
406 	while (start < end) {
407 		mid = start + (end - start) / 2;
408 		/*
409 		 * start <= mid < end
410 		 * data->comp[start].ohm > ohm >= data->comp[end].ohm
411 		 *
412 		 * We could check for "ohm == data->comp[mid].ohm" here, but
413 		 * that is a quite unlikely condition, and we would have to
414 		 * check again after updating start. Check it at the end instead
415 		 * for simplicity.
416 		 */
417 		if (ohm >= data->comp[mid].ohm) {
418 			end = mid;
419 		} else {
420 			start = mid + 1;
421 			/*
422 			 * ohm >= data->comp[start].ohm might be true here,
423 			 * since we set start to mid + 1. In that case, we are
424 			 * done. We could keep going, but the condition is quite
425 			 * likely to occur, so it is worth checking for it.
426 			 */
427 			if (ohm >= data->comp[start].ohm)
428 				end = start;
429 		}
430 		/*
431 		 * start <= end
432 		 * data->comp[start].ohm >= ohm >= data->comp[end].ohm
433 		 */
434 	}
435 	/*
436 	 * start == end
437 	 * ohm >= data->comp[end].ohm
438 	 */
439 	*i_low = end;
440 	if (ohm == data->comp[end].ohm)
441 		*i_high = end;
442 	else
443 		*i_high = end - 1;
444 }
445 
446 static int get_temp_mc(struct ntc_data *data, unsigned int ohm)
447 {
448 	int low, high;
449 	int temp;
450 
451 	lookup_comp(data, ohm, &low, &high);
452 	if (low == high) {
453 		/* Unable to use linear approximation */
454 		temp = data->comp[low].temp_c * 1000;
455 	} else {
456 		temp = data->comp[low].temp_c * 1000 +
457 			((data->comp[high].temp_c - data->comp[low].temp_c) *
458 			 1000 * ((int)ohm - (int)data->comp[low].ohm)) /
459 			((int)data->comp[high].ohm - (int)data->comp[low].ohm);
460 	}
461 	return temp;
462 }
463 
464 static int ntc_thermistor_get_ohm(struct ntc_data *data)
465 {
466 	int read_uv;
467 
468 	if (data->pdata->read_ohm)
469 		return data->pdata->read_ohm();
470 
471 	if (data->pdata->read_uv) {
472 		read_uv = data->pdata->read_uv(data->pdata);
473 		if (read_uv < 0)
474 			return read_uv;
475 		return get_ohm_of_thermistor(data, read_uv);
476 	}
477 	return -EINVAL;
478 }
479 
480 static int ntc_read_temp(void *dev, int *temp)
481 {
482 	struct ntc_data *data = dev_get_drvdata(dev);
483 	int ohm;
484 
485 	ohm = ntc_thermistor_get_ohm(data);
486 	if (ohm < 0)
487 		return ohm;
488 
489 	*temp = get_temp_mc(data, ohm);
490 
491 	return 0;
492 }
493 
494 static ssize_t ntc_show_name(struct device *dev,
495 		struct device_attribute *attr, char *buf)
496 {
497 	struct ntc_data *data = dev_get_drvdata(dev);
498 
499 	return sprintf(buf, "%s\n", data->name);
500 }
501 
502 static ssize_t ntc_show_type(struct device *dev,
503 		struct device_attribute *attr, char *buf)
504 {
505 	return sprintf(buf, "4\n");
506 }
507 
508 static ssize_t ntc_show_temp(struct device *dev,
509 		struct device_attribute *attr, char *buf)
510 {
511 	struct ntc_data *data = dev_get_drvdata(dev);
512 	int ohm;
513 
514 	ohm = ntc_thermistor_get_ohm(data);
515 	if (ohm < 0)
516 		return ohm;
517 
518 	return sprintf(buf, "%d\n", get_temp_mc(data, ohm));
519 }
520 
521 static SENSOR_DEVICE_ATTR(temp1_type, S_IRUGO, ntc_show_type, NULL, 0);
522 static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, ntc_show_temp, NULL, 0);
523 static DEVICE_ATTR(name, S_IRUGO, ntc_show_name, NULL);
524 
525 static struct attribute *ntc_attributes[] = {
526 	&dev_attr_name.attr,
527 	&sensor_dev_attr_temp1_type.dev_attr.attr,
528 	&sensor_dev_attr_temp1_input.dev_attr.attr,
529 	NULL,
530 };
531 
532 static const struct attribute_group ntc_attr_group = {
533 	.attrs = ntc_attributes,
534 };
535 
536 static const struct thermal_zone_of_device_ops ntc_of_thermal_ops = {
537 	.get_temp = ntc_read_temp,
538 };
539 
540 static int ntc_thermistor_probe(struct platform_device *pdev)
541 {
542 	const struct of_device_id *of_id =
543 			of_match_device(of_match_ptr(ntc_match), &pdev->dev);
544 	const struct platform_device_id *pdev_id;
545 	struct ntc_thermistor_platform_data *pdata;
546 	struct ntc_data *data;
547 	int ret;
548 
549 	pdata = ntc_thermistor_parse_dt(pdev);
550 	if (IS_ERR(pdata))
551 		return PTR_ERR(pdata);
552 	else if (pdata == NULL)
553 		pdata = dev_get_platdata(&pdev->dev);
554 
555 	if (!pdata) {
556 		dev_err(&pdev->dev, "No platform init data supplied.\n");
557 		return -ENODEV;
558 	}
559 
560 	/* Either one of the two is required. */
561 	if (!pdata->read_uv && !pdata->read_ohm) {
562 		dev_err(&pdev->dev,
563 			"Both read_uv and read_ohm missing. Need either one of the two.\n");
564 		return -EINVAL;
565 	}
566 
567 	if (pdata->read_uv && pdata->read_ohm) {
568 		dev_warn(&pdev->dev,
569 			 "Only one of read_uv and read_ohm is needed; ignoring read_uv.\n");
570 		pdata->read_uv = NULL;
571 	}
572 
573 	if (pdata->read_uv && (pdata->pullup_uv == 0 ||
574 				(pdata->pullup_ohm == 0 && pdata->connect ==
575 				 NTC_CONNECTED_GROUND) ||
576 				(pdata->pulldown_ohm == 0 && pdata->connect ==
577 				 NTC_CONNECTED_POSITIVE) ||
578 				(pdata->connect != NTC_CONNECTED_POSITIVE &&
579 				 pdata->connect != NTC_CONNECTED_GROUND))) {
580 		dev_err(&pdev->dev,
581 			"Required data to use read_uv not supplied.\n");
582 		return -EINVAL;
583 	}
584 
585 	data = devm_kzalloc(&pdev->dev, sizeof(struct ntc_data), GFP_KERNEL);
586 	if (!data)
587 		return -ENOMEM;
588 
589 	pdev_id = of_id ? of_id->data : platform_get_device_id(pdev);
590 
591 	data->dev = &pdev->dev;
592 	data->pdata = pdata;
593 	strlcpy(data->name, pdev_id->name, sizeof(data->name));
594 
595 	switch (pdev_id->driver_data) {
596 	case TYPE_NCPXXWB473:
597 		data->comp = ncpXXwb473;
598 		data->n_comp = ARRAY_SIZE(ncpXXwb473);
599 		break;
600 	case TYPE_NCPXXWL333:
601 		data->comp = ncpXXwl333;
602 		data->n_comp = ARRAY_SIZE(ncpXXwl333);
603 		break;
604 	case TYPE_B57330V2103:
605 		data->comp = b57330v2103;
606 		data->n_comp = ARRAY_SIZE(b57330v2103);
607 		break;
608 	case TYPE_NCPXXWF104:
609 		data->comp = ncpXXwf104;
610 		data->n_comp = ARRAY_SIZE(ncpXXwf104);
611 		break;
612 	default:
613 		dev_err(&pdev->dev, "Unknown device type: %lu(%s)\n",
614 				pdev_id->driver_data, pdev_id->name);
615 		return -EINVAL;
616 	}
617 
618 	platform_set_drvdata(pdev, data);
619 
620 	ret = sysfs_create_group(&data->dev->kobj, &ntc_attr_group);
621 	if (ret) {
622 		dev_err(data->dev, "unable to create sysfs files\n");
623 		return ret;
624 	}
625 
626 	data->hwmon_dev = hwmon_device_register(data->dev);
627 	if (IS_ERR(data->hwmon_dev)) {
628 		dev_err(data->dev, "unable to register as hwmon device.\n");
629 		ret = PTR_ERR(data->hwmon_dev);
630 		goto err_after_sysfs;
631 	}
632 
633 	dev_info(&pdev->dev, "Thermistor type: %s successfully probed.\n",
634 								pdev_id->name);
635 
636 	data->tz = thermal_zone_of_sensor_register(data->dev, 0, data->dev,
637 						   &ntc_of_thermal_ops);
638 	if (IS_ERR(data->tz)) {
639 		dev_dbg(&pdev->dev, "Failed to register to thermal fw.\n");
640 		data->tz = NULL;
641 	}
642 
643 	return 0;
644 err_after_sysfs:
645 	sysfs_remove_group(&data->dev->kobj, &ntc_attr_group);
646 	ntc_iio_channel_release(pdata);
647 	return ret;
648 }
649 
650 static int ntc_thermistor_remove(struct platform_device *pdev)
651 {
652 	struct ntc_data *data = platform_get_drvdata(pdev);
653 	struct ntc_thermistor_platform_data *pdata = data->pdata;
654 
655 	hwmon_device_unregister(data->hwmon_dev);
656 	sysfs_remove_group(&data->dev->kobj, &ntc_attr_group);
657 	ntc_iio_channel_release(pdata);
658 
659 	thermal_zone_of_sensor_unregister(data->dev, data->tz);
660 
661 	return 0;
662 }
663 
664 static struct platform_driver ntc_thermistor_driver = {
665 	.driver = {
666 		.name = "ntc-thermistor",
667 		.of_match_table = of_match_ptr(ntc_match),
668 	},
669 	.probe = ntc_thermistor_probe,
670 	.remove = ntc_thermistor_remove,
671 	.id_table = ntc_thermistor_id,
672 };
673 
674 module_platform_driver(ntc_thermistor_driver);
675 
676 MODULE_DESCRIPTION("NTC Thermistor Driver");
677 MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
678 MODULE_LICENSE("GPL");
679 MODULE_ALIAS("platform:ntc-thermistor");
680