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/kernel.h>
11 #include <linux/module.h>
12 #include <linux/platform_device.h>
13 #include <linux/slab.h>
14 #include <linux/thermal.h>
15
16 #include "thermal_hwmon.h"
17
18 struct gadc_thermal_info {
19 struct device *dev;
20 struct thermal_zone_device *tz_dev;
21 struct iio_channel *channel;
22 s32 *lookup_table;
23 int nlookup_table;
24 };
25
gadc_thermal_adc_to_temp(struct gadc_thermal_info * gti,int val)26 static int gadc_thermal_adc_to_temp(struct gadc_thermal_info *gti, int val)
27 {
28 int temp, temp_hi, temp_lo, adc_hi, adc_lo;
29 int i;
30
31 if (!gti->lookup_table)
32 return val;
33
34 for (i = 0; i < gti->nlookup_table; i++) {
35 if (val >= gti->lookup_table[2 * i + 1])
36 break;
37 }
38
39 if (i == 0) {
40 temp = gti->lookup_table[0];
41 } else if (i >= gti->nlookup_table) {
42 temp = gti->lookup_table[2 * (gti->nlookup_table - 1)];
43 } else {
44 adc_hi = gti->lookup_table[2 * i - 1];
45 adc_lo = gti->lookup_table[2 * i + 1];
46
47 temp_hi = gti->lookup_table[2 * i - 2];
48 temp_lo = gti->lookup_table[2 * i];
49
50 temp = temp_hi + mult_frac(temp_lo - temp_hi, val - adc_hi,
51 adc_lo - adc_hi);
52 }
53
54 return temp;
55 }
56
gadc_thermal_get_temp(struct thermal_zone_device * tz,int * temp)57 static int gadc_thermal_get_temp(struct thermal_zone_device *tz, int *temp)
58 {
59 struct gadc_thermal_info *gti = thermal_zone_device_priv(tz);
60 int val;
61 int ret;
62
63 ret = iio_read_channel_processed(gti->channel, &val);
64 if (ret < 0)
65 return ret;
66
67 *temp = gadc_thermal_adc_to_temp(gti, val);
68
69 return 0;
70 }
71
72 static const struct thermal_zone_device_ops gadc_thermal_ops = {
73 .get_temp = gadc_thermal_get_temp,
74 };
75
gadc_thermal_read_linear_lookup_table(struct device * dev,struct gadc_thermal_info * gti)76 static int gadc_thermal_read_linear_lookup_table(struct device *dev,
77 struct gadc_thermal_info *gti)
78 {
79 struct device_node *np = dev->of_node;
80 enum iio_chan_type chan_type;
81 int ntable;
82 int ret;
83
84 ntable = of_property_count_elems_of_size(np, "temperature-lookup-table",
85 sizeof(u32));
86 if (ntable <= 0) {
87 ret = iio_get_channel_type(gti->channel, &chan_type);
88 if (ret || chan_type != IIO_TEMP)
89 dev_notice(dev,
90 "no lookup table, assuming DAC channel returns milliCelcius\n");
91 return 0;
92 }
93
94 if (ntable % 2) {
95 dev_err(dev, "Pair of temperature vs ADC read value missing\n");
96 return -EINVAL;
97 }
98
99 gti->lookup_table = devm_kcalloc(dev,
100 ntable, sizeof(*gti->lookup_table),
101 GFP_KERNEL);
102 if (!gti->lookup_table)
103 return -ENOMEM;
104
105 ret = of_property_read_u32_array(np, "temperature-lookup-table",
106 (u32 *)gti->lookup_table, ntable);
107 if (ret < 0) {
108 dev_err(dev, "Failed to read temperature lookup table: %d\n",
109 ret);
110 return ret;
111 }
112
113 gti->nlookup_table = ntable / 2;
114
115 return 0;
116 }
117
gadc_thermal_probe(struct platform_device * pdev)118 static int gadc_thermal_probe(struct platform_device *pdev)
119 {
120 struct device *dev = &pdev->dev;
121 struct gadc_thermal_info *gti;
122 int ret;
123
124 if (!dev->of_node) {
125 dev_err(dev, "Only DT based supported\n");
126 return -ENODEV;
127 }
128
129 gti = devm_kzalloc(dev, sizeof(*gti), GFP_KERNEL);
130 if (!gti)
131 return -ENOMEM;
132
133 gti->channel = devm_iio_channel_get(dev, "sensor-channel");
134 if (IS_ERR(gti->channel))
135 return dev_err_probe(dev, PTR_ERR(gti->channel), "IIO channel not found\n");
136
137 ret = gadc_thermal_read_linear_lookup_table(dev, gti);
138 if (ret < 0)
139 return ret;
140
141 gti->dev = dev;
142
143 gti->tz_dev = devm_thermal_of_zone_register(dev, 0, gti,
144 &gadc_thermal_ops);
145 if (IS_ERR(gti->tz_dev)) {
146 ret = PTR_ERR(gti->tz_dev);
147 if (ret != -EPROBE_DEFER)
148 dev_err(dev,
149 "Thermal zone sensor register failed: %d\n",
150 ret);
151 return ret;
152 }
153
154 devm_thermal_add_hwmon_sysfs(dev, gti->tz_dev);
155
156 return 0;
157 }
158
159 static const struct of_device_id of_adc_thermal_match[] = {
160 { .compatible = "generic-adc-thermal", },
161 {},
162 };
163 MODULE_DEVICE_TABLE(of, of_adc_thermal_match);
164
165 static struct platform_driver gadc_thermal_driver = {
166 .driver = {
167 .name = "generic-adc-thermal",
168 .of_match_table = of_adc_thermal_match,
169 },
170 .probe = gadc_thermal_probe,
171 };
172
173 module_platform_driver(gadc_thermal_driver);
174
175 MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
176 MODULE_DESCRIPTION("Generic ADC thermal driver using IIO framework with DT");
177 MODULE_LICENSE("GPL v2");
178