thermal-generic-adc.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Generic ADC thermal driver
  4 *
  5 * Copyright (C) 2016 NVIDIA CORPORATION. All rights reserved.
  6 *
  7 * Author: Laxman Dewangan <ldewangan@nvidia.com>
  8 */
  9#include <linux/iio/consumer.h>
 10#include <linux/iio/iio.h>
 11#include <linux/kernel.h>
 12#include <linux/module.h>
 13#include <linux/platform_device.h>
 14#include <linux/slab.h>
 15#include <linux/thermal.h>
 16
 17#include "thermal_hwmon.h"
 18
 19struct gadc_thermal_info {
 20	struct device *dev;
 21	struct thermal_zone_device *tz_dev;
 22	struct iio_channel *channel;
 23	s32 *lookup_table;
 24	int nlookup_table;
 25};
 26
 27static int gadc_thermal_adc_to_temp(struct gadc_thermal_info *gti, int val)
 28{
 29	int temp, temp_hi, temp_lo, adc_hi, adc_lo;
 30	int i;
 31
 32	if (!gti->lookup_table)
 33		return val;
 34
 35	for (i = 0; i < gti->nlookup_table; i++) {
 36		if (val >= gti->lookup_table[2 * i + 1])
 37			break;
 38	}
 39
 40	if (i == 0) {
 41		temp = gti->lookup_table[0];
 42	} else if (i >= gti->nlookup_table) {
 43		temp = gti->lookup_table[2 * (gti->nlookup_table - 1)];
 44	} else {
 45		adc_hi = gti->lookup_table[2 * i - 1];
 46		adc_lo = gti->lookup_table[2 * i + 1];
 47
 48		temp_hi = gti->lookup_table[2 * i - 2];
 49		temp_lo = gti->lookup_table[2 * i];
 50
 51		temp = temp_hi + mult_frac(temp_lo - temp_hi, val - adc_hi,
 52					   adc_lo - adc_hi);
 53	}
 54
 55	return temp;
 56}
 57
 58static int gadc_thermal_get_temp(struct thermal_zone_device *tz, int *temp)
 59{
 60	struct gadc_thermal_info *gti = thermal_zone_device_priv(tz);
 61	int val;
 62	int ret;
 63
 64	ret = iio_read_channel_processed(gti->channel, &val);
 65	if (ret < 0)
 66		return ret;
 67
 68	*temp = gadc_thermal_adc_to_temp(gti, val);
 69
 70	return 0;
 71}
 72
 73static const struct thermal_zone_device_ops gadc_thermal_ops = {
 74	.get_temp = gadc_thermal_get_temp,
 75};
 76
 77static const struct iio_chan_spec gadc_thermal_iio_channels[] = {
 78	{
 79		.type = IIO_TEMP,
 80		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
 81	}
 82};
 83
 84static int gadc_thermal_read_raw(struct iio_dev *indio_dev,
 85				 struct iio_chan_spec const *chan,
 86				 int *val, int *val2, long mask)
 87{
 88	struct gadc_thermal_info *gtinfo = iio_priv(indio_dev);
 89	int ret;
 90
 91	switch (mask) {
 92	case IIO_CHAN_INFO_PROCESSED:
 93		ret = gadc_thermal_get_temp(gtinfo->tz_dev, val);
 94		if (ret)
 95			return ret;
 96
 97		return IIO_VAL_INT;
 98
 99	default:
100		return -EINVAL;
101	}
102}
103
104static const struct iio_info gadc_thermal_iio_info = {
105	.read_raw = gadc_thermal_read_raw,
106};
107
108static int gadc_iio_register(struct device *dev, struct gadc_thermal_info *gti)
109{
110	struct gadc_thermal_info *gtinfo;
111	struct iio_dev *indio_dev;
112
113	indio_dev = devm_iio_device_alloc(dev, sizeof(*gtinfo));
114	if (!indio_dev)
115		return -ENOMEM;
116
117	gtinfo = iio_priv(indio_dev);
118	memcpy(gtinfo, gti, sizeof(*gtinfo));
119
120	indio_dev->name = dev_name(dev);
121	indio_dev->info = &gadc_thermal_iio_info;
122	indio_dev->modes = INDIO_DIRECT_MODE;
123	indio_dev->channels = gadc_thermal_iio_channels;
124	indio_dev->num_channels = ARRAY_SIZE(gadc_thermal_iio_channels);
125
126	return devm_iio_device_register(dev, indio_dev);
127}
128
129static int gadc_thermal_read_linear_lookup_table(struct device *dev,
130						 struct gadc_thermal_info *gti)
131{
132	struct device_node *np = dev->of_node;
133	enum iio_chan_type chan_type;
134	int ntable;
135	int ret;
136
137	ntable = of_property_count_elems_of_size(np, "temperature-lookup-table",
138						 sizeof(u32));
139	if (ntable <= 0) {
140		ret = iio_get_channel_type(gti->channel, &chan_type);
141		if (ret || chan_type != IIO_TEMP)
142			dev_notice(dev,
143				   "no lookup table, assuming DAC channel returns milliCelcius\n");
144		return 0;
145	}
146
147	if (ntable % 2) {
148		dev_err(dev, "Pair of temperature vs ADC read value missing\n");
149		return -EINVAL;
150	}
151
152	gti->lookup_table = devm_kcalloc(dev,
153					 ntable, sizeof(*gti->lookup_table),
154					 GFP_KERNEL);
155	if (!gti->lookup_table)
156		return -ENOMEM;
157
158	ret = of_property_read_u32_array(np, "temperature-lookup-table",
159					 (u32 *)gti->lookup_table, ntable);
160	if (ret < 0) {
161		dev_err(dev, "Failed to read temperature lookup table: %d\n",
162			ret);
163		return ret;
164	}
165
166	gti->nlookup_table = ntable / 2;
167
168	return 0;
169}
170
171static int gadc_thermal_probe(struct platform_device *pdev)
172{
173	struct device *dev = &pdev->dev;
174	struct gadc_thermal_info *gti;
175	int ret;
176
177	if (!dev->of_node) {
178		dev_err(dev, "Only DT based supported\n");
179		return -ENODEV;
180	}
181
182	gti = devm_kzalloc(dev, sizeof(*gti), GFP_KERNEL);
183	if (!gti)
184		return -ENOMEM;
185
186	gti->channel = devm_iio_channel_get(dev, "sensor-channel");
187	if (IS_ERR(gti->channel))
188		return dev_err_probe(dev, PTR_ERR(gti->channel), "IIO channel not found\n");
189
190	ret = gadc_thermal_read_linear_lookup_table(dev, gti);
191	if (ret < 0)
192		return ret;
193
194	gti->dev = dev;
195
196	gti->tz_dev = devm_thermal_of_zone_register(dev, 0, gti,
197						    &gadc_thermal_ops);
198	if (IS_ERR(gti->tz_dev)) {
199		ret = PTR_ERR(gti->tz_dev);
200		if (ret != -EPROBE_DEFER)
201			dev_err(dev,
202				"Thermal zone sensor register failed: %d\n",
203				ret);
204		return ret;
205	}
206
207	devm_thermal_add_hwmon_sysfs(dev, gti->tz_dev);
208
209	return gadc_iio_register(&pdev->dev, gti);
210}
211
212static const struct of_device_id of_adc_thermal_match[] = {
213	{ .compatible = "generic-adc-thermal", },
214	{},
215};
216MODULE_DEVICE_TABLE(of, of_adc_thermal_match);
217
218static struct platform_driver gadc_thermal_driver = {
219	.driver = {
220		.name = "generic-adc-thermal",
221		.of_match_table = of_adc_thermal_match,
222	},
223	.probe = gadc_thermal_probe,
224};
225
226module_platform_driver(gadc_thermal_driver);
227
228MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
229MODULE_DESCRIPTION("Generic ADC thermal driver using IIO framework with DT");
230MODULE_LICENSE("GPL v2");