ntc_thermistor.c

  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
 20enum ntc_thermistor_type {
 21	TYPE_B57330V2103,
 22	TYPE_B57891S0103,
 23	TYPE_NCPXXWB473,
 24	TYPE_NCPXXWF104,
 25	TYPE_NCPXXWL333,
 26	TYPE_NCPXXXH103,
 27	TYPE_NCPXXWM474,
 28};
 29
 30struct ntc_compensation {
 31	int		temp_c;
 32	unsigned int	ohm;
 33};
 34
 35/*
 36 * Used as index in a zero-terminated array, holes not allowed so
 37 * that NTC_LAST is the first empty array entry.
 38 */
 39enum {
 40	NTC_B57330V2103,
 41	NTC_B57891S0103,
 42	NTC_NCP03WB473,
 43	NTC_NCP03WF104,
 44	NTC_NCP15WB473,
 45	NTC_NCP15WL333,
 46	NTC_NCP15XH103,
 47	NTC_NCP18WB473,
 48	NTC_NCP21WB473,
 49	NTC_SSG1404001221,
 50	NTC_NCP18WM474,
 51	NTC_LAST,
 52};
 53
 54static const struct platform_device_id ntc_thermistor_id[] = {
 55	[NTC_B57330V2103]     = { "b57330v2103",     TYPE_B57330V2103 },
 56	[NTC_B57891S0103]     = { "b57891s0103",     TYPE_B57891S0103 },
 57	[NTC_NCP03WB473]      = { "ncp03wb473",      TYPE_NCPXXWB473 },
 58	[NTC_NCP03WF104]      = { "ncp03wf104",      TYPE_NCPXXWF104 },
 59	[NTC_NCP15WB473]      = { "ncp15wb473",      TYPE_NCPXXWB473 },
 60	[NTC_NCP15WL333]      = { "ncp15wl333",      TYPE_NCPXXWL333 },
 61	[NTC_NCP15XH103]      = { "ncp15xh103",      TYPE_NCPXXXH103 },
 62	[NTC_NCP18WB473]      = { "ncp18wb473",      TYPE_NCPXXWB473 },
 63	[NTC_NCP21WB473]      = { "ncp21wb473",      TYPE_NCPXXWB473 },
 64	[NTC_SSG1404001221]   = { "ssg1404_001221",  TYPE_NCPXXWB473 },
 65	[NTC_NCP18WM474]      = { "ncp18wm474",      TYPE_NCPXXWM474 },
 66	[NTC_LAST]            = { },
 67};
 68MODULE_DEVICE_TABLE(platform, ntc_thermistor_id);
 69
 70/*
 71 * A compensation table should be sorted by the values of .ohm
 72 * in descending order.
 73 * The following compensation tables are from the specification of Murata NTC
 74 * Thermistors Datasheet
 75 */
 76static const struct ntc_compensation ncpXXwb473[] = {
 77	{ .temp_c	= -40, .ohm	= 1747920 },
 78	{ .temp_c	= -35, .ohm	= 1245428 },
 79	{ .temp_c	= -30, .ohm	= 898485 },
 80	{ .temp_c	= -25, .ohm	= 655802 },
 81	{ .temp_c	= -20, .ohm	= 483954 },
 82	{ .temp_c	= -15, .ohm	= 360850 },
 83	{ .temp_c	= -10, .ohm	= 271697 },
 84	{ .temp_c	= -5, .ohm	= 206463 },
 85	{ .temp_c	= 0, .ohm	= 158214 },
 86	{ .temp_c	= 5, .ohm	= 122259 },
 87	{ .temp_c	= 10, .ohm	= 95227 },
 88	{ .temp_c	= 15, .ohm	= 74730 },
 89	{ .temp_c	= 20, .ohm	= 59065 },
 90	{ .temp_c	= 25, .ohm	= 47000 },
 91	{ .temp_c	= 30, .ohm	= 37643 },
 92	{ .temp_c	= 35, .ohm	= 30334 },
 93	{ .temp_c	= 40, .ohm	= 24591 },
 94	{ .temp_c	= 45, .ohm	= 20048 },
 95	{ .temp_c	= 50, .ohm	= 16433 },
 96	{ .temp_c	= 55, .ohm	= 13539 },
 97	{ .temp_c	= 60, .ohm	= 11209 },
 98	{ .temp_c	= 65, .ohm	= 9328 },
 99	{ .temp_c	= 70, .ohm	= 7798 },
100	{ .temp_c	= 75, .ohm	= 6544 },
101	{ .temp_c	= 80, .ohm	= 5518 },
102	{ .temp_c	= 85, .ohm	= 4674 },
103	{ .temp_c	= 90, .ohm	= 3972 },
104	{ .temp_c	= 95, .ohm	= 3388 },
105	{ .temp_c	= 100, .ohm	= 2902 },
106	{ .temp_c	= 105, .ohm	= 2494 },
107	{ .temp_c	= 110, .ohm	= 2150 },
108	{ .temp_c	= 115, .ohm	= 1860 },
109	{ .temp_c	= 120, .ohm	= 1615 },
110	{ .temp_c	= 125, .ohm	= 1406 },
111};
112static const struct ntc_compensation ncpXXwl333[] = {
113	{ .temp_c	= -40, .ohm	= 1610154 },
114	{ .temp_c	= -35, .ohm	= 1130850 },
115	{ .temp_c	= -30, .ohm	= 802609 },
116	{ .temp_c	= -25, .ohm	= 575385 },
117	{ .temp_c	= -20, .ohm	= 416464 },
118	{ .temp_c	= -15, .ohm	= 304219 },
119	{ .temp_c	= -10, .ohm	= 224193 },
120	{ .temp_c	= -5, .ohm	= 166623 },
121	{ .temp_c	= 0, .ohm	= 124850 },
122	{ .temp_c	= 5, .ohm	= 94287 },
123	{ .temp_c	= 10, .ohm	= 71747 },
124	{ .temp_c	= 15, .ohm	= 54996 },
125	{ .temp_c	= 20, .ohm	= 42455 },
126	{ .temp_c	= 25, .ohm	= 33000 },
127	{ .temp_c	= 30, .ohm	= 25822 },
128	{ .temp_c	= 35, .ohm	= 20335 },
129	{ .temp_c	= 40, .ohm	= 16115 },
130	{ .temp_c	= 45, .ohm	= 12849 },
131	{ .temp_c	= 50, .ohm	= 10306 },
132	{ .temp_c	= 55, .ohm	= 8314 },
133	{ .temp_c	= 60, .ohm	= 6746 },
134	{ .temp_c	= 65, .ohm	= 5503 },
135	{ .temp_c	= 70, .ohm	= 4513 },
136	{ .temp_c	= 75, .ohm	= 3721 },
137	{ .temp_c	= 80, .ohm	= 3084 },
138	{ .temp_c	= 85, .ohm	= 2569 },
139	{ .temp_c	= 90, .ohm	= 2151 },
140	{ .temp_c	= 95, .ohm	= 1809 },
141	{ .temp_c	= 100, .ohm	= 1529 },
142	{ .temp_c	= 105, .ohm	= 1299 },
143	{ .temp_c	= 110, .ohm	= 1108 },
144	{ .temp_c	= 115, .ohm	= 949 },
145	{ .temp_c	= 120, .ohm	= 817 },
146	{ .temp_c	= 125, .ohm	= 707 },
147};
148
149static const struct ntc_compensation ncpXXwf104[] = {
150	{ .temp_c	= -40, .ohm	= 4397119 },
151	{ .temp_c	= -35, .ohm	= 3088599 },
152	{ .temp_c	= -30, .ohm	= 2197225 },
153	{ .temp_c	= -25, .ohm	= 1581881 },
154	{ .temp_c	= -20, .ohm	= 1151037 },
155	{ .temp_c	= -15, .ohm	= 846579 },
156	{ .temp_c	= -10, .ohm	= 628988 },
157	{ .temp_c	= -5, .ohm	= 471632 },
158	{ .temp_c	= 0, .ohm	= 357012 },
159	{ .temp_c	= 5, .ohm	= 272500 },
160	{ .temp_c	= 10, .ohm	= 209710 },
161	{ .temp_c	= 15, .ohm	= 162651 },
162	{ .temp_c	= 20, .ohm	= 127080 },
163	{ .temp_c	= 25, .ohm	= 100000 },
164	{ .temp_c	= 30, .ohm	= 79222 },
165	{ .temp_c	= 35, .ohm	= 63167 },
166	{ .temp_c	= 40, .ohm	= 50677 },
167	{ .temp_c	= 45, .ohm	= 40904 },
168	{ .temp_c	= 50, .ohm	= 33195 },
169	{ .temp_c	= 55, .ohm	= 27091 },
170	{ .temp_c	= 60, .ohm	= 22224 },
171	{ .temp_c	= 65, .ohm	= 18323 },
172	{ .temp_c	= 70, .ohm	= 15184 },
173	{ .temp_c	= 75, .ohm	= 12635 },
174	{ .temp_c	= 80, .ohm	= 10566 },
175	{ .temp_c	= 85, .ohm	= 8873 },
176	{ .temp_c	= 90, .ohm	= 7481 },
177	{ .temp_c	= 95, .ohm	= 6337 },
178	{ .temp_c	= 100, .ohm	= 5384 },
179	{ .temp_c	= 105, .ohm	= 4594 },
180	{ .temp_c	= 110, .ohm	= 3934 },
181	{ .temp_c	= 115, .ohm	= 3380 },
182	{ .temp_c	= 120, .ohm	= 2916 },
183	{ .temp_c	= 125, .ohm	= 2522 },
184};
185
186static const struct ntc_compensation ncpXXxh103[] = {
187	{ .temp_c	= -40, .ohm	= 195652 },
188	{ .temp_c	= -35, .ohm	= 148171 },
189	{ .temp_c	= -30, .ohm	= 113347 },
190	{ .temp_c	= -25, .ohm	= 87559 },
191	{ .temp_c	= -20, .ohm	= 68237 },
192	{ .temp_c	= -15, .ohm	= 53650 },
193	{ .temp_c	= -10, .ohm	= 42506 },
194	{ .temp_c	= -5, .ohm	= 33892 },
195	{ .temp_c	= 0, .ohm	= 27219 },
196	{ .temp_c	= 5, .ohm	= 22021 },
197	{ .temp_c	= 10, .ohm	= 17926 },
198	{ .temp_c	= 15, .ohm	= 14674 },
199	{ .temp_c	= 20, .ohm	= 12081 },
200	{ .temp_c	= 25, .ohm	= 10000 },
201	{ .temp_c	= 30, .ohm	= 8315 },
202	{ .temp_c	= 35, .ohm	= 6948 },
203	{ .temp_c	= 40, .ohm	= 5834 },
204	{ .temp_c	= 45, .ohm	= 4917 },
205	{ .temp_c	= 50, .ohm	= 4161 },
206	{ .temp_c	= 55, .ohm	= 3535 },
207	{ .temp_c	= 60, .ohm	= 3014 },
208	{ .temp_c	= 65, .ohm	= 2586 },
209	{ .temp_c	= 70, .ohm	= 2228 },
210	{ .temp_c	= 75, .ohm	= 1925 },
211	{ .temp_c	= 80, .ohm	= 1669 },
212	{ .temp_c	= 85, .ohm	= 1452 },
213	{ .temp_c	= 90, .ohm	= 1268 },
214	{ .temp_c	= 95, .ohm	= 1110 },
215	{ .temp_c	= 100, .ohm	= 974 },
216	{ .temp_c	= 105, .ohm	= 858 },
217	{ .temp_c	= 110, .ohm	= 758 },
218	{ .temp_c	= 115, .ohm	= 672 },
219	{ .temp_c	= 120, .ohm	= 596 },
220	{ .temp_c	= 125, .ohm	= 531 },
221};
222
223static const struct ntc_compensation ncpXXwm474[] = {
224	{ .temp_c	= -40, .ohm	= 10900000 },
225	{ .temp_c	= -35, .ohm	= 9600000 },
226	{ .temp_c	= -30, .ohm	= 8300000 },
227	{ .temp_c	= -25, .ohm	= 7000000 },
228	{ .temp_c	= -20, .ohm	= 5980000 },
229	{ .temp_c	= -15, .ohm	= 4960000 },
230	{ .temp_c	= -10, .ohm	= 3940000 },
231	{ .temp_c	= -5, .ohm	= 2920000 },
232	{ .temp_c	= 0, .ohm	= 1900000 },
233	{ .temp_c	= 5, .ohm	= 1614000 },
234	{ .temp_c	= 10, .ohm	= 1328000 },
235	{ .temp_c	= 15, .ohm	= 1042000 },
236	{ .temp_c	= 20, .ohm	= 756000 },
237	{ .temp_c	= 25, .ohm	= 470000 },
238	{ .temp_c	= 30, .ohm	= 404000 },
239	{ .temp_c	= 35, .ohm	= 338000 },
240	{ .temp_c	= 40, .ohm	= 272000 },
241	{ .temp_c	= 45, .ohm	= 206000 },
242	{ .temp_c	= 50, .ohm	= 140000 },
243	{ .temp_c	= 55, .ohm	= 122000 },
244	{ .temp_c	= 60, .ohm	= 104000 },
245	{ .temp_c	= 65, .ohm	= 86000 },
246	{ .temp_c	= 70, .ohm	= 68000 },
247	{ .temp_c	= 75, .ohm	= 50000 },
248	{ .temp_c	= 80, .ohm	= 44200 },
249	{ .temp_c	= 85, .ohm	= 38400 },
250	{ .temp_c	= 90, .ohm	= 32600 },
251	{ .temp_c	= 95, .ohm	= 26800 },
252	{ .temp_c	= 100, .ohm	= 21000 },
253	{ .temp_c	= 105, .ohm	= 18600 },
254	{ .temp_c	= 110, .ohm	= 16200 },
255	{ .temp_c	= 115, .ohm	= 13800 },
256	{ .temp_c	= 120, .ohm	= 11400 },
257	{ .temp_c	= 125, .ohm	= 9000 },
258};
259
260/*
261 * The following compensation tables are from the specifications in EPCOS NTC
262 * Thermistors Datasheets
263 */
264static const struct ntc_compensation b57330v2103[] = {
265	{ .temp_c	= -40, .ohm	= 190030 },
266	{ .temp_c	= -35, .ohm	= 145360 },
267	{ .temp_c	= -30, .ohm	= 112060 },
268	{ .temp_c	= -25, .ohm	= 87041 },
269	{ .temp_c	= -20, .ohm	= 68104 },
270	{ .temp_c	= -15, .ohm	= 53665 },
271	{ .temp_c	= -10, .ohm	= 42576 },
272	{ .temp_c	= -5, .ohm	= 34001 },
273	{ .temp_c	= 0, .ohm	= 27326 },
274	{ .temp_c	= 5, .ohm	= 22096 },
275	{ .temp_c	= 10, .ohm	= 17973 },
276	{ .temp_c	= 15, .ohm	= 14703 },
277	{ .temp_c	= 20, .ohm	= 12090 },
278	{ .temp_c	= 25, .ohm	= 10000 },
279	{ .temp_c	= 30, .ohm	= 8311 },
280	{ .temp_c	= 35, .ohm	= 6941 },
281	{ .temp_c	= 40, .ohm	= 5825 },
282	{ .temp_c	= 45, .ohm	= 4911 },
283	{ .temp_c	= 50, .ohm	= 4158 },
284	{ .temp_c	= 55, .ohm	= 3536 },
285	{ .temp_c	= 60, .ohm	= 3019 },
286	{ .temp_c	= 65, .ohm	= 2588 },
287	{ .temp_c	= 70, .ohm	= 2227 },
288	{ .temp_c	= 75, .ohm	= 1924 },
289	{ .temp_c	= 80, .ohm	= 1668 },
290	{ .temp_c	= 85, .ohm	= 1451 },
291	{ .temp_c	= 90, .ohm	= 1266 },
292	{ .temp_c	= 95, .ohm	= 1108 },
293	{ .temp_c	= 100, .ohm	= 973 },
294	{ .temp_c	= 105, .ohm	= 857 },
295	{ .temp_c	= 110, .ohm	= 757 },
296	{ .temp_c	= 115, .ohm	= 671 },
297	{ .temp_c	= 120, .ohm	= 596 },
298	{ .temp_c	= 125, .ohm	= 531 },
299};
300
301static const struct ntc_compensation b57891s0103[] = {
302	{ .temp_c	= -55.0, .ohm	= 878900 },
303	{ .temp_c	= -50.0, .ohm	= 617590 },
304	{ .temp_c	= -45.0, .ohm	= 439340 },
305	{ .temp_c	= -40.0, .ohm	= 316180 },
306	{ .temp_c	= -35.0, .ohm	= 230060 },
307	{ .temp_c	= -30.0, .ohm	= 169150 },
308	{ .temp_c	= -25.0, .ohm	= 125550 },
309	{ .temp_c	= -20.0, .ohm	= 94143 },
310	{ .temp_c	= -15.0, .ohm	= 71172 },
311	{ .temp_c	= -10.0, .ohm	= 54308 },
312	{ .temp_c	= -5.0, .ohm	= 41505 },
313	{ .temp_c	= 0.0, .ohm	= 32014 },
314	{ .temp_c	= 5.0, .ohm	= 25011 },
315	{ .temp_c	= 10.0, .ohm	= 19691 },
316	{ .temp_c	= 15.0, .ohm	= 15618 },
317	{ .temp_c	= 20.0, .ohm	= 12474 },
318	{ .temp_c	= 25.0, .ohm	= 10000 },
319	{ .temp_c	= 30.0, .ohm	= 8080 },
320	{ .temp_c	= 35.0, .ohm	= 6569 },
321	{ .temp_c	= 40.0, .ohm	= 5372 },
322	{ .temp_c	= 45.0, .ohm	= 4424 },
323	{ .temp_c	= 50.0, .ohm	= 3661 },
324	{ .temp_c	= 55.0, .ohm	= 3039 },
325	{ .temp_c	= 60.0, .ohm	= 2536 },
326	{ .temp_c	= 65.0, .ohm	= 2128 },
327	{ .temp_c	= 70.0, .ohm	= 1794 },
328	{ .temp_c	= 75.0, .ohm	= 1518 },
329	{ .temp_c	= 80.0, .ohm	= 1290 },
330	{ .temp_c	= 85.0, .ohm	= 1100 },
331	{ .temp_c	= 90.0, .ohm	= 942 },
332	{ .temp_c	= 95.0, .ohm	= 809 },
333	{ .temp_c	= 100.0, .ohm	= 697 },
334	{ .temp_c	= 105.0, .ohm	= 604 },
335	{ .temp_c	= 110.0, .ohm	= 525 },
336	{ .temp_c	= 115.0, .ohm	= 457 },
337	{ .temp_c	= 120.0, .ohm	= 400 },
338	{ .temp_c	= 125.0, .ohm	= 351 },
339	{ .temp_c	= 130.0, .ohm	= 308 },
340	{ .temp_c	= 135.0, .ohm	= 272 },
341	{ .temp_c	= 140.0, .ohm	= 240 },
342	{ .temp_c	= 145.0, .ohm	= 213 },
343	{ .temp_c	= 150.0, .ohm	= 189 },
344	{ .temp_c	= 155.0, .ohm	= 168 },
345};
346
347struct ntc_type {
348	const struct ntc_compensation *comp;
349	int n_comp;
350};
351
352#define NTC_TYPE(ntc, compensation) \
353[(ntc)] = { .comp = (compensation), .n_comp = ARRAY_SIZE(compensation) }
354
355static const struct ntc_type ntc_type[] = {
356	NTC_TYPE(TYPE_B57330V2103, b57330v2103),
357	NTC_TYPE(TYPE_B57891S0103, b57891s0103),
358	NTC_TYPE(TYPE_NCPXXWB473,  ncpXXwb473),
359	NTC_TYPE(TYPE_NCPXXWF104,  ncpXXwf104),
360	NTC_TYPE(TYPE_NCPXXWL333,  ncpXXwl333),
361	NTC_TYPE(TYPE_NCPXXXH103,  ncpXXxh103),
362	NTC_TYPE(TYPE_NCPXXWM474,  ncpXXwm474),
363};
364
365/*
366 * pullup_uV, pullup_ohm, pulldown_ohm, and connect are required.
367 *
368 * How to setup pullup_ohm, pulldown_ohm, and connect is
369 * described at Documentation/hwmon/ntc_thermistor.rst
370 *
371 * pullup/down_ohm: 0 for infinite / not-connected
372 *
373 * chan: iio_channel pointer to communicate with the ADC which the
374 * thermistor is using for conversion of the analog values.
375 */
376struct ntc_data {
377	const struct ntc_compensation *comp;
378	int n_comp;
379	unsigned int pullup_uv;
380	unsigned int pullup_ohm;
381	unsigned int pulldown_ohm;
382	enum { NTC_CONNECTED_POSITIVE, NTC_CONNECTED_GROUND } connect;
383	struct iio_channel *chan;
384};
385
386static int ntc_adc_iio_read(struct ntc_data *data)
387{
388	struct iio_channel *channel = data->chan;
389	int uv, ret;
390
391	ret = iio_read_channel_processed_scale(channel, &uv, 1000);
392	if (ret < 0) {
393		int raw;
394
395		/*
396		 * This fallback uses a raw read and then
397		 * assumes the ADC is 12 bits, scaling with
398		 * a factor 1000 to get to microvolts.
399		 */
400		ret = iio_read_channel_raw(channel, &raw);
401		if (ret < 0) {
402			pr_err("read channel() error: %d\n", ret);
403			return ret;
404		}
405		ret = iio_convert_raw_to_processed(channel, raw, &uv, 1000);
406		if (ret < 0) {
407			/* Assume 12 bit ADC with vref at pullup_uv */
408			uv = (data->pullup_uv * (s64)raw) >> 12;
409		}
410	}
411
412	return uv;
413}
414
415static inline u64 div64_u64_safe(u64 dividend, u64 divisor)
416{
417	if (divisor == 0 && dividend == 0)
418		return 0;
419	if (divisor == 0)
420		return UINT_MAX;
421	return div64_u64(dividend, divisor);
422}
423
424static int get_ohm_of_thermistor(struct ntc_data *data, unsigned int uv)
425{
426	u32 puv = data->pullup_uv;
427	u64 n, puo, pdo;
428	puo = data->pullup_ohm;
429	pdo = data->pulldown_ohm;
430
431	/* faulty adc value */
432	if (uv == 0 || uv >= puv)
433		return -ENODATA;
434
435	if (data->connect == NTC_CONNECTED_POSITIVE && puo == 0)
436		n = div_u64(pdo * (puv - uv), uv);
437	else if (data->connect == NTC_CONNECTED_GROUND && pdo == 0)
438		n = div_u64(puo * uv, puv - uv);
439	else if (data->connect == NTC_CONNECTED_POSITIVE)
440		n = div64_u64_safe(pdo * puo * (puv - uv),
441				puo * uv - pdo * (puv - uv));
442	else
443		n = div64_u64_safe(pdo * puo * uv, pdo * (puv - uv) - puo * uv);
444
445	/* sensor out of bounds */
446	if (n > data->comp[0].ohm || n < data->comp[data->n_comp - 1].ohm)
447		return -ENODATA;
448
449	return n;
450}
451
452static void lookup_comp(struct ntc_data *data, unsigned int ohm,
453			int *i_low, int *i_high)
454{
455	int start, end, mid;
456
457	/*
458	 * Handle special cases: Resistance is higher than or equal to
459	 * resistance in first table entry, or resistance is lower or equal
460	 * to resistance in last table entry.
461	 * In these cases, return i_low == i_high, either pointing to the
462	 * beginning or to the end of the table depending on the condition.
463	 */
464	if (ohm >= data->comp[0].ohm) {
465		*i_low = 0;
466		*i_high = 0;
467		return;
468	}
469	if (ohm <= data->comp[data->n_comp - 1].ohm) {
470		*i_low = data->n_comp - 1;
471		*i_high = data->n_comp - 1;
472		return;
473	}
474
475	/* Do a binary search on compensation table */
476	start = 0;
477	end = data->n_comp;
478	while (start < end) {
479		mid = start + (end - start) / 2;
480		/*
481		 * start <= mid < end
482		 * data->comp[start].ohm > ohm >= data->comp[end].ohm
483		 *
484		 * We could check for "ohm == data->comp[mid].ohm" here, but
485		 * that is a quite unlikely condition, and we would have to
486		 * check again after updating start. Check it at the end instead
487		 * for simplicity.
488		 */
489		if (ohm >= data->comp[mid].ohm) {
490			end = mid;
491		} else {
492			start = mid + 1;
493			/*
494			 * ohm >= data->comp[start].ohm might be true here,
495			 * since we set start to mid + 1. In that case, we are
496			 * done. We could keep going, but the condition is quite
497			 * likely to occur, so it is worth checking for it.
498			 */
499			if (ohm >= data->comp[start].ohm)
500				end = start;
501		}
502		/*
503		 * start <= end
504		 * data->comp[start].ohm >= ohm >= data->comp[end].ohm
505		 */
506	}
507	/*
508	 * start == end
509	 * ohm >= data->comp[end].ohm
510	 */
511	*i_low = end;
512	if (ohm == data->comp[end].ohm)
513		*i_high = end;
514	else
515		*i_high = end - 1;
516}
517
518static int get_temp_mc(struct ntc_data *data, unsigned int ohm)
519{
520	int low, high;
521	int temp;
522
523	lookup_comp(data, ohm, &low, &high);
524	/*
525	 * First multiplying the table temperatures with 1000 to get to
526	 * millicentigrades (which is what we want) and then interpolating
527	 * will give the best precision.
528	 */
529	temp = fixp_linear_interpolate(data->comp[low].ohm,
530				       data->comp[low].temp_c * 1000,
531				       data->comp[high].ohm,
532				       data->comp[high].temp_c * 1000,
533				       ohm);
534	return temp;
535}
536
537static int ntc_thermistor_get_ohm(struct ntc_data *data)
538{
539	int read_uv;
540
541	read_uv = ntc_adc_iio_read(data);
542	if (read_uv < 0)
543		return read_uv;
544	return get_ohm_of_thermistor(data, read_uv);
545}
546
547static int ntc_read(struct device *dev, enum hwmon_sensor_types type,
548		    u32 attr, int channel, long *val)
549{
550	struct ntc_data *data = dev_get_drvdata(dev);
551	int ohm;
552
553	switch (type) {
554	case hwmon_temp:
555		switch (attr) {
556		case hwmon_temp_input:
557			ohm = ntc_thermistor_get_ohm(data);
558			if (ohm < 0)
559				return ohm;
560			*val = get_temp_mc(data, ohm);
561			return 0;
562		case hwmon_temp_type:
563			*val = 4;
564			return 0;
565		default:
566			break;
567		}
568		break;
569	default:
570		break;
571	}
572	return -EINVAL;
573}
574
575static umode_t ntc_is_visible(const void *data, enum hwmon_sensor_types type,
576			      u32 attr, int channel)
577{
578	if (type == hwmon_temp) {
579		switch (attr) {
580		case hwmon_temp_input:
581		case hwmon_temp_type:
582			return 0444;
583		default:
584			break;
585		}
586	}
587	return 0;
588}
589
590static const struct hwmon_channel_info * const ntc_info[] = {
591	HWMON_CHANNEL_INFO(chip, HWMON_C_REGISTER_TZ),
592	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT | HWMON_T_TYPE),
593	NULL
594};
595
596static const struct hwmon_ops ntc_hwmon_ops = {
597	.is_visible = ntc_is_visible,
598	.read = ntc_read,
599};
600
601static const struct hwmon_chip_info ntc_chip_info = {
602	.ops = &ntc_hwmon_ops,
603	.info = ntc_info,
604};
605
606static int ntc_thermistor_parse_props(struct device *dev,
607				      struct ntc_data *data)
608{
609	struct iio_channel *chan;
610	enum iio_chan_type type;
611	int ret;
612
613	chan = devm_iio_channel_get(dev, NULL);
614	if (IS_ERR(chan))
615		return PTR_ERR(chan);
616
617	ret = iio_get_channel_type(chan, &type);
618	if (ret < 0)
619		return ret;
620
621	if (type != IIO_VOLTAGE)
622		return -EINVAL;
623
624	ret = device_property_read_u32(dev, "pullup-uv", &data->pullup_uv);
625	if (ret)
626		return dev_err_probe(dev,  ret, "pullup-uv not specified\n");
627
628	ret = device_property_read_u32(dev, "pullup-ohm", &data->pullup_ohm);
629	if (ret)
630		return dev_err_probe(dev,  ret, "pullup-ohm not specified\n");
631
632	ret = device_property_read_u32(dev, "pulldown-ohm", &data->pulldown_ohm);
633	if (ret)
634		return dev_err_probe(dev,  ret, "pulldown-ohm not specified\n");
635
636	if (device_property_read_bool(dev, "connected-positive"))
637		data->connect = NTC_CONNECTED_POSITIVE;
638	else /* status change should be possible if not always on. */
639		data->connect = NTC_CONNECTED_GROUND;
640
641	data->chan = chan;
642
643	return 0;
644}
645
646static int ntc_thermistor_probe(struct platform_device *pdev)
647{
648	struct device *dev = &pdev->dev;
649	const struct platform_device_id *pdev_id;
650	struct device *hwmon_dev;
651	struct ntc_data *data;
652	int ret;
653
654	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
655	if (!data)
656		return -ENOMEM;
657
658	ret = ntc_thermistor_parse_props(dev, data);
659	if (ret)
660		return ret;
661
662	if (data->pullup_uv == 0 ||
663	    (data->pullup_ohm == 0 && data->connect ==
664	     NTC_CONNECTED_GROUND) ||
665	    (data->pulldown_ohm == 0 && data->connect ==
666	     NTC_CONNECTED_POSITIVE) ||
667	    (data->connect != NTC_CONNECTED_POSITIVE &&
668	     data->connect != NTC_CONNECTED_GROUND)) {
669		dev_err(dev, "Required data to use NTC driver not supplied.\n");
670		return -EINVAL;
671	}
672
673	pdev_id = device_get_match_data(dev);
674
675	if (pdev_id->driver_data >= ARRAY_SIZE(ntc_type)) {
676		dev_err(dev, "Unknown device type: %lu(%s)\n",
677				pdev_id->driver_data, pdev_id->name);
678		return -EINVAL;
679	}
680
681	data->comp   = ntc_type[pdev_id->driver_data].comp;
682	data->n_comp = ntc_type[pdev_id->driver_data].n_comp;
683
684	hwmon_dev = devm_hwmon_device_register_with_info(dev, pdev_id->name,
685							 data, &ntc_chip_info,
686							 NULL);
687	if (IS_ERR(hwmon_dev)) {
688		dev_err(dev, "unable to register as hwmon device.\n");
689		return PTR_ERR(hwmon_dev);
690	}
691
692	dev_info(dev, "Thermistor type: %s successfully probed.\n",
693		 pdev_id->name);
694
695	return 0;
696}
697
698static const struct of_device_id ntc_match[] = {
699	{ .compatible = "epcos,b57330v2103",
700		.data = &ntc_thermistor_id[NTC_B57330V2103]},
701	{ .compatible = "epcos,b57891s0103",
702		.data = &ntc_thermistor_id[NTC_B57891S0103] },
703	{ .compatible = "murata,ncp03wb473",
704		.data = &ntc_thermistor_id[NTC_NCP03WB473] },
705	{ .compatible = "murata,ncp03wf104",
706		.data = &ntc_thermistor_id[NTC_NCP03WF104] },
707	{ .compatible = "murata,ncp15wb473",
708		.data = &ntc_thermistor_id[NTC_NCP15WB473] },
709	{ .compatible = "murata,ncp15wl333",
710		.data = &ntc_thermistor_id[NTC_NCP15WL333] },
711	{ .compatible = "murata,ncp15xh103",
712		.data = &ntc_thermistor_id[NTC_NCP15XH103] },
713	{ .compatible = "murata,ncp18wb473",
714		.data = &ntc_thermistor_id[NTC_NCP18WB473] },
715	{ .compatible = "murata,ncp21wb473",
716		.data = &ntc_thermistor_id[NTC_NCP21WB473] },
717	{ .compatible = "samsung,1404-001221",
718		.data = &ntc_thermistor_id[NTC_SSG1404001221] },
719	{ .compatible = "murata,ncp18wm474",
720		.data = &ntc_thermistor_id[NTC_NCP18WM474] },
721
722	/* Usage of vendor name "ntc" is deprecated */
723	{ .compatible = "ntc,ncp03wb473",
724		.data = &ntc_thermistor_id[NTC_NCP03WB473] },
725	{ .compatible = "ntc,ncp15wb473",
726		.data = &ntc_thermistor_id[NTC_NCP15WB473] },
727	{ .compatible = "ntc,ncp15wl333",
728		.data = &ntc_thermistor_id[NTC_NCP15WL333] },
729	{ .compatible = "ntc,ncp18wb473",
730		.data = &ntc_thermistor_id[NTC_NCP18WB473] },
731	{ .compatible = "ntc,ncp21wb473",
732		.data = &ntc_thermistor_id[NTC_NCP21WB473] },
733	{ },
734};
735MODULE_DEVICE_TABLE(of, ntc_match);
736
737static struct platform_driver ntc_thermistor_driver = {
738	.driver = {
739		.name = "ntc-thermistor",
740		.of_match_table = ntc_match,
741	},
742	.probe = ntc_thermistor_probe,
743	.id_table = ntc_thermistor_id,
744};
745
746module_platform_driver(ntc_thermistor_driver);
747
748MODULE_DESCRIPTION("NTC Thermistor Driver");
749MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
750MODULE_LICENSE("GPL");
751MODULE_ALIAS("platform:ntc-thermistor");