1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * ntc_thermistor.c - NTC Thermistors
4  *
5  *  Copyright (C) 2010 Samsung Electronics
6  *  MyungJoo Ham <myungjoo.ham@samsung.com>
7  */
8 
9 #include <linux/slab.h>
10 #include <linux/module.h>
11 #include <linux/math64.h>
12 #include <linux/mod_devicetable.h>
13 #include <linux/platform_device.h>
14 #include <linux/property.h>
15 #include <linux/err.h>
16 #include <linux/fixp-arith.h>
17 #include <linux/iio/consumer.h>
18 #include <linux/hwmon.h>
19 
20 enum ntc_thermistor_type {
21 	TYPE_B57330V2103,
22 	TYPE_B57891S0103,
23 	TYPE_NCPXXWB473,
24 	TYPE_NCPXXWF104,
25 	TYPE_NCPXXWL333,
26 	TYPE_NCPXXXH103,
27 };
28 
29 struct ntc_compensation {
30 	int		temp_c;
31 	unsigned int	ohm;
32 };
33 
34 /*
35  * Used as index in a zero-terminated array, holes not allowed so
36  * that NTC_LAST is the first empty array entry.
37  */
38 enum {
39 	NTC_B57330V2103,
40 	NTC_B57891S0103,
41 	NTC_NCP03WB473,
42 	NTC_NCP03WF104,
43 	NTC_NCP15WB473,
44 	NTC_NCP15WL333,
45 	NTC_NCP15XH103,
46 	NTC_NCP18WB473,
47 	NTC_NCP21WB473,
48 	NTC_SSG1404001221,
49 	NTC_LAST,
50 };
51 
52 static const struct platform_device_id ntc_thermistor_id[] = {
53 	[NTC_B57330V2103]     = { "b57330v2103",     TYPE_B57330V2103 },
54 	[NTC_B57891S0103]     = { "b57891s0103",     TYPE_B57891S0103 },
55 	[NTC_NCP03WB473]      = { "ncp03wb473",      TYPE_NCPXXWB473 },
56 	[NTC_NCP03WF104]      = { "ncp03wf104",      TYPE_NCPXXWF104 },
57 	[NTC_NCP15WB473]      = { "ncp15wb473",      TYPE_NCPXXWB473 },
58 	[NTC_NCP15WL333]      = { "ncp15wl333",      TYPE_NCPXXWL333 },
59 	[NTC_NCP15XH103]      = { "ncp15xh103",      TYPE_NCPXXXH103 },
60 	[NTC_NCP18WB473]      = { "ncp18wb473",      TYPE_NCPXXWB473 },
61 	[NTC_NCP21WB473]      = { "ncp21wb473",      TYPE_NCPXXWB473 },
62 	[NTC_SSG1404001221]   = { "ssg1404_001221",  TYPE_NCPXXWB473 },
63 	[NTC_LAST]            = { },
64 };
65 
66 /*
67  * A compensation table should be sorted by the values of .ohm
68  * in descending order.
69  * The following compensation tables are from the specification of Murata NTC
70  * Thermistors Datasheet
71  */
72 static const struct ntc_compensation ncpXXwb473[] = {
73 	{ .temp_c	= -40, .ohm	= 1747920 },
74 	{ .temp_c	= -35, .ohm	= 1245428 },
75 	{ .temp_c	= -30, .ohm	= 898485 },
76 	{ .temp_c	= -25, .ohm	= 655802 },
77 	{ .temp_c	= -20, .ohm	= 483954 },
78 	{ .temp_c	= -15, .ohm	= 360850 },
79 	{ .temp_c	= -10, .ohm	= 271697 },
80 	{ .temp_c	= -5, .ohm	= 206463 },
81 	{ .temp_c	= 0, .ohm	= 158214 },
82 	{ .temp_c	= 5, .ohm	= 122259 },
83 	{ .temp_c	= 10, .ohm	= 95227 },
84 	{ .temp_c	= 15, .ohm	= 74730 },
85 	{ .temp_c	= 20, .ohm	= 59065 },
86 	{ .temp_c	= 25, .ohm	= 47000 },
87 	{ .temp_c	= 30, .ohm	= 37643 },
88 	{ .temp_c	= 35, .ohm	= 30334 },
89 	{ .temp_c	= 40, .ohm	= 24591 },
90 	{ .temp_c	= 45, .ohm	= 20048 },
91 	{ .temp_c	= 50, .ohm	= 16433 },
92 	{ .temp_c	= 55, .ohm	= 13539 },
93 	{ .temp_c	= 60, .ohm	= 11209 },
94 	{ .temp_c	= 65, .ohm	= 9328 },
95 	{ .temp_c	= 70, .ohm	= 7798 },
96 	{ .temp_c	= 75, .ohm	= 6544 },
97 	{ .temp_c	= 80, .ohm	= 5518 },
98 	{ .temp_c	= 85, .ohm	= 4674 },
99 	{ .temp_c	= 90, .ohm	= 3972 },
100 	{ .temp_c	= 95, .ohm	= 3388 },
101 	{ .temp_c	= 100, .ohm	= 2902 },
102 	{ .temp_c	= 105, .ohm	= 2494 },
103 	{ .temp_c	= 110, .ohm	= 2150 },
104 	{ .temp_c	= 115, .ohm	= 1860 },
105 	{ .temp_c	= 120, .ohm	= 1615 },
106 	{ .temp_c	= 125, .ohm	= 1406 },
107 };
108 static const struct ntc_compensation ncpXXwl333[] = {
109 	{ .temp_c	= -40, .ohm	= 1610154 },
110 	{ .temp_c	= -35, .ohm	= 1130850 },
111 	{ .temp_c	= -30, .ohm	= 802609 },
112 	{ .temp_c	= -25, .ohm	= 575385 },
113 	{ .temp_c	= -20, .ohm	= 416464 },
114 	{ .temp_c	= -15, .ohm	= 304219 },
115 	{ .temp_c	= -10, .ohm	= 224193 },
116 	{ .temp_c	= -5, .ohm	= 166623 },
117 	{ .temp_c	= 0, .ohm	= 124850 },
118 	{ .temp_c	= 5, .ohm	= 94287 },
119 	{ .temp_c	= 10, .ohm	= 71747 },
120 	{ .temp_c	= 15, .ohm	= 54996 },
121 	{ .temp_c	= 20, .ohm	= 42455 },
122 	{ .temp_c	= 25, .ohm	= 33000 },
123 	{ .temp_c	= 30, .ohm	= 25822 },
124 	{ .temp_c	= 35, .ohm	= 20335 },
125 	{ .temp_c	= 40, .ohm	= 16115 },
126 	{ .temp_c	= 45, .ohm	= 12849 },
127 	{ .temp_c	= 50, .ohm	= 10306 },
128 	{ .temp_c	= 55, .ohm	= 8314 },
129 	{ .temp_c	= 60, .ohm	= 6746 },
130 	{ .temp_c	= 65, .ohm	= 5503 },
131 	{ .temp_c	= 70, .ohm	= 4513 },
132 	{ .temp_c	= 75, .ohm	= 3721 },
133 	{ .temp_c	= 80, .ohm	= 3084 },
134 	{ .temp_c	= 85, .ohm	= 2569 },
135 	{ .temp_c	= 90, .ohm	= 2151 },
136 	{ .temp_c	= 95, .ohm	= 1809 },
137 	{ .temp_c	= 100, .ohm	= 1529 },
138 	{ .temp_c	= 105, .ohm	= 1299 },
139 	{ .temp_c	= 110, .ohm	= 1108 },
140 	{ .temp_c	= 115, .ohm	= 949 },
141 	{ .temp_c	= 120, .ohm	= 817 },
142 	{ .temp_c	= 125, .ohm	= 707 },
143 };
144 
145 static const struct ntc_compensation ncpXXwf104[] = {
146 	{ .temp_c	= -40, .ohm	= 4397119 },
147 	{ .temp_c	= -35, .ohm	= 3088599 },
148 	{ .temp_c	= -30, .ohm	= 2197225 },
149 	{ .temp_c	= -25, .ohm	= 1581881 },
150 	{ .temp_c	= -20, .ohm	= 1151037 },
151 	{ .temp_c	= -15, .ohm	= 846579 },
152 	{ .temp_c	= -10, .ohm	= 628988 },
153 	{ .temp_c	= -5, .ohm	= 471632 },
154 	{ .temp_c	= 0, .ohm	= 357012 },
155 	{ .temp_c	= 5, .ohm	= 272500 },
156 	{ .temp_c	= 10, .ohm	= 209710 },
157 	{ .temp_c	= 15, .ohm	= 162651 },
158 	{ .temp_c	= 20, .ohm	= 127080 },
159 	{ .temp_c	= 25, .ohm	= 100000 },
160 	{ .temp_c	= 30, .ohm	= 79222 },
161 	{ .temp_c	= 35, .ohm	= 63167 },
162 	{ .temp_c	= 40, .ohm	= 50677 },
163 	{ .temp_c	= 45, .ohm	= 40904 },
164 	{ .temp_c	= 50, .ohm	= 33195 },
165 	{ .temp_c	= 55, .ohm	= 27091 },
166 	{ .temp_c	= 60, .ohm	= 22224 },
167 	{ .temp_c	= 65, .ohm	= 18323 },
168 	{ .temp_c	= 70, .ohm	= 15184 },
169 	{ .temp_c	= 75, .ohm	= 12635 },
170 	{ .temp_c	= 80, .ohm	= 10566 },
171 	{ .temp_c	= 85, .ohm	= 8873 },
172 	{ .temp_c	= 90, .ohm	= 7481 },
173 	{ .temp_c	= 95, .ohm	= 6337 },
174 	{ .temp_c	= 100, .ohm	= 5384 },
175 	{ .temp_c	= 105, .ohm	= 4594 },
176 	{ .temp_c	= 110, .ohm	= 3934 },
177 	{ .temp_c	= 115, .ohm	= 3380 },
178 	{ .temp_c	= 120, .ohm	= 2916 },
179 	{ .temp_c	= 125, .ohm	= 2522 },
180 };
181 
182 static const struct ntc_compensation ncpXXxh103[] = {
183 	{ .temp_c	= -40, .ohm	= 247565 },
184 	{ .temp_c	= -35, .ohm	= 181742 },
185 	{ .temp_c	= -30, .ohm	= 135128 },
186 	{ .temp_c	= -25, .ohm	= 101678 },
187 	{ .temp_c	= -20, .ohm	= 77373 },
188 	{ .temp_c	= -15, .ohm	= 59504 },
189 	{ .temp_c	= -10, .ohm	= 46222 },
190 	{ .temp_c	= -5, .ohm	= 36244 },
191 	{ .temp_c	= 0, .ohm	= 28674 },
192 	{ .temp_c	= 5, .ohm	= 22878 },
193 	{ .temp_c	= 10, .ohm	= 18399 },
194 	{ .temp_c	= 15, .ohm	= 14910 },
195 	{ .temp_c	= 20, .ohm	= 12169 },
196 	{ .temp_c	= 25, .ohm	= 10000 },
197 	{ .temp_c	= 30, .ohm	= 8271 },
198 	{ .temp_c	= 35, .ohm	= 6883 },
199 	{ .temp_c	= 40, .ohm	= 5762 },
200 	{ .temp_c	= 45, .ohm	= 4851 },
201 	{ .temp_c	= 50, .ohm	= 4105 },
202 	{ .temp_c	= 55, .ohm	= 3492 },
203 	{ .temp_c	= 60, .ohm	= 2985 },
204 	{ .temp_c	= 65, .ohm	= 2563 },
205 	{ .temp_c	= 70, .ohm	= 2211 },
206 	{ .temp_c	= 75, .ohm	= 1915 },
207 	{ .temp_c	= 80, .ohm	= 1666 },
208 	{ .temp_c	= 85, .ohm	= 1454 },
209 	{ .temp_c	= 90, .ohm	= 1275 },
210 	{ .temp_c	= 95, .ohm	= 1121 },
211 	{ .temp_c	= 100, .ohm	= 990 },
212 	{ .temp_c	= 105, .ohm	= 876 },
213 	{ .temp_c	= 110, .ohm	= 779 },
214 	{ .temp_c	= 115, .ohm	= 694 },
215 	{ .temp_c	= 120, .ohm	= 620 },
216 	{ .temp_c	= 125, .ohm	= 556 },
217 };
218 
219 /*
220  * The following compensation tables are from the specifications in EPCOS NTC
221  * Thermistors Datasheets
222  */
223 static const struct ntc_compensation b57330v2103[] = {
224 	{ .temp_c	= -40, .ohm	= 190030 },
225 	{ .temp_c	= -35, .ohm	= 145360 },
226 	{ .temp_c	= -30, .ohm	= 112060 },
227 	{ .temp_c	= -25, .ohm	= 87041 },
228 	{ .temp_c	= -20, .ohm	= 68104 },
229 	{ .temp_c	= -15, .ohm	= 53665 },
230 	{ .temp_c	= -10, .ohm	= 42576 },
231 	{ .temp_c	= -5, .ohm	= 34001 },
232 	{ .temp_c	= 0, .ohm	= 27326 },
233 	{ .temp_c	= 5, .ohm	= 22096 },
234 	{ .temp_c	= 10, .ohm	= 17973 },
235 	{ .temp_c	= 15, .ohm	= 14703 },
236 	{ .temp_c	= 20, .ohm	= 12090 },
237 	{ .temp_c	= 25, .ohm	= 10000 },
238 	{ .temp_c	= 30, .ohm	= 8311 },
239 	{ .temp_c	= 35, .ohm	= 6941 },
240 	{ .temp_c	= 40, .ohm	= 5825 },
241 	{ .temp_c	= 45, .ohm	= 4911 },
242 	{ .temp_c	= 50, .ohm	= 4158 },
243 	{ .temp_c	= 55, .ohm	= 3536 },
244 	{ .temp_c	= 60, .ohm	= 3019 },
245 	{ .temp_c	= 65, .ohm	= 2588 },
246 	{ .temp_c	= 70, .ohm	= 2227 },
247 	{ .temp_c	= 75, .ohm	= 1924 },
248 	{ .temp_c	= 80, .ohm	= 1668 },
249 	{ .temp_c	= 85, .ohm	= 1451 },
250 	{ .temp_c	= 90, .ohm	= 1266 },
251 	{ .temp_c	= 95, .ohm	= 1108 },
252 	{ .temp_c	= 100, .ohm	= 973 },
253 	{ .temp_c	= 105, .ohm	= 857 },
254 	{ .temp_c	= 110, .ohm	= 757 },
255 	{ .temp_c	= 115, .ohm	= 671 },
256 	{ .temp_c	= 120, .ohm	= 596 },
257 	{ .temp_c	= 125, .ohm	= 531 },
258 };
259 
260 static const struct ntc_compensation b57891s0103[] = {
261 	{ .temp_c	= -55.0, .ohm	= 878900 },
262 	{ .temp_c	= -50.0, .ohm	= 617590 },
263 	{ .temp_c	= -45.0, .ohm	= 439340 },
264 	{ .temp_c	= -40.0, .ohm	= 316180 },
265 	{ .temp_c	= -35.0, .ohm	= 230060 },
266 	{ .temp_c	= -30.0, .ohm	= 169150 },
267 	{ .temp_c	= -25.0, .ohm	= 125550 },
268 	{ .temp_c	= -20.0, .ohm	= 94143 },
269 	{ .temp_c	= -15.0, .ohm	= 71172 },
270 	{ .temp_c	= -10.0, .ohm	= 54308 },
271 	{ .temp_c	= -5.0, .ohm	= 41505 },
272 	{ .temp_c	= 0.0, .ohm	= 32014 },
273 	{ .temp_c	= 5.0, .ohm	= 25011 },
274 	{ .temp_c	= 10.0, .ohm	= 19691 },
275 	{ .temp_c	= 15.0, .ohm	= 15618 },
276 	{ .temp_c	= 20.0, .ohm	= 12474 },
277 	{ .temp_c	= 25.0, .ohm	= 10000 },
278 	{ .temp_c	= 30.0, .ohm	= 8080 },
279 	{ .temp_c	= 35.0, .ohm	= 6569 },
280 	{ .temp_c	= 40.0, .ohm	= 5372 },
281 	{ .temp_c	= 45.0, .ohm	= 4424 },
282 	{ .temp_c	= 50.0, .ohm	= 3661 },
283 	{ .temp_c	= 55.0, .ohm	= 3039 },
284 	{ .temp_c	= 60.0, .ohm	= 2536 },
285 	{ .temp_c	= 65.0, .ohm	= 2128 },
286 	{ .temp_c	= 70.0, .ohm	= 1794 },
287 	{ .temp_c	= 75.0, .ohm	= 1518 },
288 	{ .temp_c	= 80.0, .ohm	= 1290 },
289 	{ .temp_c	= 85.0, .ohm	= 1100 },
290 	{ .temp_c	= 90.0, .ohm	= 942 },
291 	{ .temp_c	= 95.0, .ohm	= 809 },
292 	{ .temp_c	= 100.0, .ohm	= 697 },
293 	{ .temp_c	= 105.0, .ohm	= 604 },
294 	{ .temp_c	= 110.0, .ohm	= 525 },
295 	{ .temp_c	= 115.0, .ohm	= 457 },
296 	{ .temp_c	= 120.0, .ohm	= 400 },
297 	{ .temp_c	= 125.0, .ohm	= 351 },
298 	{ .temp_c	= 130.0, .ohm	= 308 },
299 	{ .temp_c	= 135.0, .ohm	= 272 },
300 	{ .temp_c	= 140.0, .ohm	= 240 },
301 	{ .temp_c	= 145.0, .ohm	= 213 },
302 	{ .temp_c	= 150.0, .ohm	= 189 },
303 	{ .temp_c	= 155.0, .ohm	= 168 },
304 };
305 
306 struct ntc_type {
307 	const struct ntc_compensation *comp;
308 	int n_comp;
309 };
310 
311 #define NTC_TYPE(ntc, compensation) \
312 [(ntc)] = { .comp = (compensation), .n_comp = ARRAY_SIZE(compensation) }
313 
314 static const struct ntc_type ntc_type[] = {
315 	NTC_TYPE(TYPE_B57330V2103, b57330v2103),
316 	NTC_TYPE(TYPE_B57891S0103, b57891s0103),
317 	NTC_TYPE(TYPE_NCPXXWB473,  ncpXXwb473),
318 	NTC_TYPE(TYPE_NCPXXWF104,  ncpXXwf104),
319 	NTC_TYPE(TYPE_NCPXXWL333,  ncpXXwl333),
320 	NTC_TYPE(TYPE_NCPXXXH103,  ncpXXxh103),
321 };
322 
323 /*
324  * pullup_uV, pullup_ohm, pulldown_ohm, and connect are required.
325  *
326  * How to setup pullup_ohm, pulldown_ohm, and connect is
327  * described at Documentation/hwmon/ntc_thermistor.rst
328  *
329  * pullup/down_ohm: 0 for infinite / not-connected
330  *
331  * chan: iio_channel pointer to communicate with the ADC which the
332  * thermistor is using for conversion of the analog values.
333  */
334 struct ntc_data {
335 	const struct ntc_compensation *comp;
336 	int n_comp;
337 	unsigned int pullup_uv;
338 	unsigned int pullup_ohm;
339 	unsigned int pulldown_ohm;
340 	enum { NTC_CONNECTED_POSITIVE, NTC_CONNECTED_GROUND } connect;
341 	struct iio_channel *chan;
342 };
343 
344 static int ntc_adc_iio_read(struct ntc_data *data)
345 {
346 	struct iio_channel *channel = data->chan;
347 	int uv, ret;
348 
349 	ret = iio_read_channel_processed_scale(channel, &uv, 1000);
350 	if (ret < 0) {
351 		int raw;
352 
353 		/*
354 		 * This fallback uses a raw read and then
355 		 * assumes the ADC is 12 bits, scaling with
356 		 * a factor 1000 to get to microvolts.
357 		 */
358 		ret = iio_read_channel_raw(channel, &raw);
359 		if (ret < 0) {
360 			pr_err("read channel() error: %d\n", ret);
361 			return ret;
362 		}
363 		ret = iio_convert_raw_to_processed(channel, raw, &uv, 1000);
364 		if (ret < 0) {
365 			/* Assume 12 bit ADC with vref at pullup_uv */
366 			uv = (data->pullup_uv * (s64)raw) >> 12;
367 		}
368 	}
369 
370 	return uv;
371 }
372 
373 static inline u64 div64_u64_safe(u64 dividend, u64 divisor)
374 {
375 	if (divisor == 0 && dividend == 0)
376 		return 0;
377 	if (divisor == 0)
378 		return UINT_MAX;
379 	return div64_u64(dividend, divisor);
380 }
381 
382 static int get_ohm_of_thermistor(struct ntc_data *data, unsigned int uv)
383 {
384 	u32 puv = data->pullup_uv;
385 	u64 n, puo, pdo;
386 	puo = data->pullup_ohm;
387 	pdo = data->pulldown_ohm;
388 
389 	if (uv == 0)
390 		return (data->connect == NTC_CONNECTED_POSITIVE) ?
391 			INT_MAX : 0;
392 	if (uv >= puv)
393 		return (data->connect == NTC_CONNECTED_POSITIVE) ?
394 			0 : INT_MAX;
395 
396 	if (data->connect == NTC_CONNECTED_POSITIVE && puo == 0)
397 		n = div_u64(pdo * (puv - uv), uv);
398 	else if (data->connect == NTC_CONNECTED_GROUND && pdo == 0)
399 		n = div_u64(puo * uv, puv - uv);
400 	else if (data->connect == NTC_CONNECTED_POSITIVE)
401 		n = div64_u64_safe(pdo * puo * (puv - uv),
402 				puo * uv - pdo * (puv - uv));
403 	else
404 		n = div64_u64_safe(pdo * puo * uv, pdo * (puv - uv) - puo * uv);
405 
406 	if (n > INT_MAX)
407 		n = INT_MAX;
408 	return n;
409 }
410 
411 static void lookup_comp(struct ntc_data *data, unsigned int ohm,
412 			int *i_low, int *i_high)
413 {
414 	int start, end, mid;
415 
416 	/*
417 	 * Handle special cases: Resistance is higher than or equal to
418 	 * resistance in first table entry, or resistance is lower or equal
419 	 * to resistance in last table entry.
420 	 * In these cases, return i_low == i_high, either pointing to the
421 	 * beginning or to the end of the table depending on the condition.
422 	 */
423 	if (ohm >= data->comp[0].ohm) {
424 		*i_low = 0;
425 		*i_high = 0;
426 		return;
427 	}
428 	if (ohm <= data->comp[data->n_comp - 1].ohm) {
429 		*i_low = data->n_comp - 1;
430 		*i_high = data->n_comp - 1;
431 		return;
432 	}
433 
434 	/* Do a binary search on compensation table */
435 	start = 0;
436 	end = data->n_comp;
437 	while (start < end) {
438 		mid = start + (end - start) / 2;
439 		/*
440 		 * start <= mid < end
441 		 * data->comp[start].ohm > ohm >= data->comp[end].ohm
442 		 *
443 		 * We could check for "ohm == data->comp[mid].ohm" here, but
444 		 * that is a quite unlikely condition, and we would have to
445 		 * check again after updating start. Check it at the end instead
446 		 * for simplicity.
447 		 */
448 		if (ohm >= data->comp[mid].ohm) {
449 			end = mid;
450 		} else {
451 			start = mid + 1;
452 			/*
453 			 * ohm >= data->comp[start].ohm might be true here,
454 			 * since we set start to mid + 1. In that case, we are
455 			 * done. We could keep going, but the condition is quite
456 			 * likely to occur, so it is worth checking for it.
457 			 */
458 			if (ohm >= data->comp[start].ohm)
459 				end = start;
460 		}
461 		/*
462 		 * start <= end
463 		 * data->comp[start].ohm >= ohm >= data->comp[end].ohm
464 		 */
465 	}
466 	/*
467 	 * start == end
468 	 * ohm >= data->comp[end].ohm
469 	 */
470 	*i_low = end;
471 	if (ohm == data->comp[end].ohm)
472 		*i_high = end;
473 	else
474 		*i_high = end - 1;
475 }
476 
477 static int get_temp_mc(struct ntc_data *data, unsigned int ohm)
478 {
479 	int low, high;
480 	int temp;
481 
482 	lookup_comp(data, ohm, &low, &high);
483 	/*
484 	 * First multiplying the table temperatures with 1000 to get to
485 	 * millicentigrades (which is what we want) and then interpolating
486 	 * will give the best precision.
487 	 */
488 	temp = fixp_linear_interpolate(data->comp[low].ohm,
489 				       data->comp[low].temp_c * 1000,
490 				       data->comp[high].ohm,
491 				       data->comp[high].temp_c * 1000,
492 				       ohm);
493 	return temp;
494 }
495 
496 static int ntc_thermistor_get_ohm(struct ntc_data *data)
497 {
498 	int read_uv;
499 
500 	read_uv = ntc_adc_iio_read(data);
501 	if (read_uv < 0)
502 		return read_uv;
503 	return get_ohm_of_thermistor(data, read_uv);
504 }
505 
506 static int ntc_read(struct device *dev, enum hwmon_sensor_types type,
507 		    u32 attr, int channel, long *val)
508 {
509 	struct ntc_data *data = dev_get_drvdata(dev);
510 	int ohm;
511 
512 	switch (type) {
513 	case hwmon_temp:
514 		switch (attr) {
515 		case hwmon_temp_input:
516 			ohm = ntc_thermistor_get_ohm(data);
517 			if (ohm < 0)
518 				return ohm;
519 			*val = get_temp_mc(data, ohm);
520 			return 0;
521 		case hwmon_temp_type:
522 			*val = 4;
523 			return 0;
524 		default:
525 			break;
526 		}
527 		break;
528 	default:
529 		break;
530 	}
531 	return -EINVAL;
532 }
533 
534 static umode_t ntc_is_visible(const void *data, enum hwmon_sensor_types type,
535 			      u32 attr, int channel)
536 {
537 	if (type == hwmon_temp) {
538 		switch (attr) {
539 		case hwmon_temp_input:
540 		case hwmon_temp_type:
541 			return 0444;
542 		default:
543 			break;
544 		}
545 	}
546 	return 0;
547 }
548 
549 static const struct hwmon_channel_info * const ntc_info[] = {
550 	HWMON_CHANNEL_INFO(chip, HWMON_C_REGISTER_TZ),
551 	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT | HWMON_T_TYPE),
552 	NULL
553 };
554 
555 static const struct hwmon_ops ntc_hwmon_ops = {
556 	.is_visible = ntc_is_visible,
557 	.read = ntc_read,
558 };
559 
560 static const struct hwmon_chip_info ntc_chip_info = {
561 	.ops = &ntc_hwmon_ops,
562 	.info = ntc_info,
563 };
564 
565 static int ntc_thermistor_parse_props(struct device *dev,
566 				      struct ntc_data *data)
567 {
568 	struct iio_channel *chan;
569 	enum iio_chan_type type;
570 	int ret;
571 
572 	chan = devm_iio_channel_get(dev, NULL);
573 	if (IS_ERR(chan))
574 		return PTR_ERR(chan);
575 
576 	ret = iio_get_channel_type(chan, &type);
577 	if (ret < 0)
578 		return ret;
579 
580 	if (type != IIO_VOLTAGE)
581 		return -EINVAL;
582 
583 	ret = device_property_read_u32(dev, "pullup-uv", &data->pullup_uv);
584 	if (ret)
585 		return dev_err_probe(dev,  ret, "pullup-uv not specified\n");
586 
587 	ret = device_property_read_u32(dev, "pullup-ohm", &data->pullup_ohm);
588 	if (ret)
589 		return dev_err_probe(dev,  ret, "pullup-ohm not specified\n");
590 
591 	ret = device_property_read_u32(dev, "pulldown-ohm", &data->pulldown_ohm);
592 	if (ret)
593 		return dev_err_probe(dev,  ret, "pulldown-ohm not specified\n");
594 
595 	if (device_property_read_bool(dev, "connected-positive"))
596 		data->connect = NTC_CONNECTED_POSITIVE;
597 	else /* status change should be possible if not always on. */
598 		data->connect = NTC_CONNECTED_GROUND;
599 
600 	data->chan = chan;
601 
602 	return 0;
603 }
604 
605 static int ntc_thermistor_probe(struct platform_device *pdev)
606 {
607 	struct device *dev = &pdev->dev;
608 	const struct platform_device_id *pdev_id;
609 	struct device *hwmon_dev;
610 	struct ntc_data *data;
611 	int ret;
612 
613 	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
614 	if (!data)
615 		return -ENOMEM;
616 
617 	ret = ntc_thermistor_parse_props(dev, data);
618 	if (ret)
619 		return ret;
620 
621 	if (data->pullup_uv == 0 ||
622 	    (data->pullup_ohm == 0 && data->connect ==
623 	     NTC_CONNECTED_GROUND) ||
624 	    (data->pulldown_ohm == 0 && data->connect ==
625 	     NTC_CONNECTED_POSITIVE) ||
626 	    (data->connect != NTC_CONNECTED_POSITIVE &&
627 	     data->connect != NTC_CONNECTED_GROUND)) {
628 		dev_err(dev, "Required data to use NTC driver not supplied.\n");
629 		return -EINVAL;
630 	}
631 
632 	pdev_id = device_get_match_data(dev);
633 
634 	if (pdev_id->driver_data >= ARRAY_SIZE(ntc_type)) {
635 		dev_err(dev, "Unknown device type: %lu(%s)\n",
636 				pdev_id->driver_data, pdev_id->name);
637 		return -EINVAL;
638 	}
639 
640 	data->comp   = ntc_type[pdev_id->driver_data].comp;
641 	data->n_comp = ntc_type[pdev_id->driver_data].n_comp;
642 
643 	hwmon_dev = devm_hwmon_device_register_with_info(dev, pdev_id->name,
644 							 data, &ntc_chip_info,
645 							 NULL);
646 	if (IS_ERR(hwmon_dev)) {
647 		dev_err(dev, "unable to register as hwmon device.\n");
648 		return PTR_ERR(hwmon_dev);
649 	}
650 
651 	dev_info(dev, "Thermistor type: %s successfully probed.\n",
652 		 pdev_id->name);
653 
654 	return 0;
655 }
656 
657 static const struct of_device_id ntc_match[] = {
658 	{ .compatible = "epcos,b57330v2103",
659 		.data = &ntc_thermistor_id[NTC_B57330V2103]},
660 	{ .compatible = "epcos,b57891s0103",
661 		.data = &ntc_thermistor_id[NTC_B57891S0103] },
662 	{ .compatible = "murata,ncp03wb473",
663 		.data = &ntc_thermistor_id[NTC_NCP03WB473] },
664 	{ .compatible = "murata,ncp03wf104",
665 		.data = &ntc_thermistor_id[NTC_NCP03WF104] },
666 	{ .compatible = "murata,ncp15wb473",
667 		.data = &ntc_thermistor_id[NTC_NCP15WB473] },
668 	{ .compatible = "murata,ncp15wl333",
669 		.data = &ntc_thermistor_id[NTC_NCP15WL333] },
670 	{ .compatible = "murata,ncp15xh103",
671 		.data = &ntc_thermistor_id[NTC_NCP15XH103] },
672 	{ .compatible = "murata,ncp18wb473",
673 		.data = &ntc_thermistor_id[NTC_NCP18WB473] },
674 	{ .compatible = "murata,ncp21wb473",
675 		.data = &ntc_thermistor_id[NTC_NCP21WB473] },
676 	{ .compatible = "samsung,1404-001221",
677 		.data = &ntc_thermistor_id[NTC_SSG1404001221] },
678 
679 	/* Usage of vendor name "ntc" is deprecated */
680 	{ .compatible = "ntc,ncp03wb473",
681 		.data = &ntc_thermistor_id[NTC_NCP03WB473] },
682 	{ .compatible = "ntc,ncp15wb473",
683 		.data = &ntc_thermistor_id[NTC_NCP15WB473] },
684 	{ .compatible = "ntc,ncp15wl333",
685 		.data = &ntc_thermistor_id[NTC_NCP15WL333] },
686 	{ .compatible = "ntc,ncp18wb473",
687 		.data = &ntc_thermistor_id[NTC_NCP18WB473] },
688 	{ .compatible = "ntc,ncp21wb473",
689 		.data = &ntc_thermistor_id[NTC_NCP21WB473] },
690 	{ },
691 };
692 MODULE_DEVICE_TABLE(of, ntc_match);
693 
694 static struct platform_driver ntc_thermistor_driver = {
695 	.driver = {
696 		.name = "ntc-thermistor",
697 		.of_match_table = ntc_match,
698 	},
699 	.probe = ntc_thermistor_probe,
700 	.id_table = ntc_thermistor_id,
701 };
702 
703 module_platform_driver(ntc_thermistor_driver);
704 
705 MODULE_DESCRIPTION("NTC Thermistor Driver");
706 MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
707 MODULE_LICENSE("GPL");
708 MODULE_ALIAS("platform:ntc-thermistor");
709