1 /*
2 * Generic ADC thermal driver
3 *
4 * Copyright (C) 2016 NVIDIA CORPORATION. All rights reserved.
5 *
6 * Author: Laxman Dewangan <ldewangan@nvidia.com>
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
11 */
12 #include <linux/iio/consumer.h>
13 #include <linux/kernel.h>
14 #include <linux/module.h>
15 #include <linux/platform_device.h>
16 #include <linux/slab.h>
17 #include <linux/thermal.h>
18
19 struct 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
gadc_thermal_adc_to_temp(struct gadc_thermal_info * gti,int val)27 static int gadc_thermal_adc_to_temp(struct gadc_thermal_info *gti, int val)
28 {
29 int temp, adc_hi, adc_lo;
30 int i;
31
32 for (i = 0; i < gti->nlookup_table; i++) {
33 if (val >= gti->lookup_table[2 * i + 1])
34 break;
35 }
36
37 if (i == 0) {
38 temp = gti->lookup_table[0];
39 } else if (i >= (gti->nlookup_table - 1)) {
40 temp = gti->lookup_table[2 * (gti->nlookup_table - 1)];
41 } else {
42 adc_hi = gti->lookup_table[2 * i - 1];
43 adc_lo = gti->lookup_table[2 * i + 1];
44 temp = gti->lookup_table[2 * i];
45 temp -= ((val - adc_lo) * 1000) / (adc_hi - adc_lo);
46 }
47
48 return temp;
49 }
50
gadc_thermal_get_temp(void * data,int * temp)51 static int gadc_thermal_get_temp(void *data, int *temp)
52 {
53 struct gadc_thermal_info *gti = data;
54 int val;
55 int ret;
56
57 ret = iio_read_channel_processed(gti->channel, &val);
58 if (ret < 0) {
59 dev_err(gti->dev, "IIO channel read failed %d\n", ret);
60 return ret;
61 }
62 *temp = gadc_thermal_adc_to_temp(gti, val);
63
64 return 0;
65 }
66
67 static const struct thermal_zone_of_device_ops gadc_thermal_ops = {
68 .get_temp = gadc_thermal_get_temp,
69 };
70
gadc_thermal_read_linear_lookup_table(struct device * dev,struct gadc_thermal_info * gti)71 static int gadc_thermal_read_linear_lookup_table(struct device *dev,
72 struct gadc_thermal_info *gti)
73 {
74 struct device_node *np = dev->of_node;
75 int ntable;
76 int ret;
77
78 ntable = of_property_count_elems_of_size(np, "temperature-lookup-table",
79 sizeof(u32));
80 if (ntable < 0) {
81 dev_err(dev, "Lookup table is not provided\n");
82 return ntable;
83 }
84
85 if (ntable % 2) {
86 dev_err(dev, "Pair of temperature vs ADC read value missing\n");
87 return -EINVAL;
88 }
89
90 gti->lookup_table = devm_kcalloc(dev,
91 ntable, sizeof(*gti->lookup_table),
92 GFP_KERNEL);
93 if (!gti->lookup_table)
94 return -ENOMEM;
95
96 ret = of_property_read_u32_array(np, "temperature-lookup-table",
97 (u32 *)gti->lookup_table, ntable);
98 if (ret < 0) {
99 dev_err(dev, "Failed to read temperature lookup table: %d\n",
100 ret);
101 return ret;
102 }
103
104 gti->nlookup_table = ntable / 2;
105
106 return 0;
107 }
108
gadc_thermal_probe(struct platform_device * pdev)109 static int gadc_thermal_probe(struct platform_device *pdev)
110 {
111 struct gadc_thermal_info *gti;
112 int ret;
113
114 if (!pdev->dev.of_node) {
115 dev_err(&pdev->dev, "Only DT based supported\n");
116 return -ENODEV;
117 }
118
119 gti = devm_kzalloc(&pdev->dev, sizeof(*gti), GFP_KERNEL);
120 if (!gti)
121 return -ENOMEM;
122
123 ret = gadc_thermal_read_linear_lookup_table(&pdev->dev, gti);
124 if (ret < 0)
125 return ret;
126
127 gti->dev = &pdev->dev;
128 platform_set_drvdata(pdev, gti);
129
130 gti->channel = devm_iio_channel_get(&pdev->dev, "sensor-channel");
131 if (IS_ERR(gti->channel)) {
132 ret = PTR_ERR(gti->channel);
133 dev_err(&pdev->dev, "IIO channel not found: %d\n", ret);
134 return ret;
135 }
136
137 gti->tz_dev = devm_thermal_zone_of_sensor_register(&pdev->dev, 0, gti,
138 &gadc_thermal_ops);
139 if (IS_ERR(gti->tz_dev)) {
140 ret = PTR_ERR(gti->tz_dev);
141 dev_err(&pdev->dev, "Thermal zone sensor register failed: %d\n",
142 ret);
143 return ret;
144 }
145
146 return 0;
147 }
148
149 static const struct of_device_id of_adc_thermal_match[] = {
150 { .compatible = "generic-adc-thermal", },
151 {},
152 };
153 MODULE_DEVICE_TABLE(of, of_adc_thermal_match);
154
155 static struct platform_driver gadc_thermal_driver = {
156 .driver = {
157 .name = "generic-adc-thermal",
158 .of_match_table = of_adc_thermal_match,
159 },
160 .probe = gadc_thermal_probe,
161 };
162
163 module_platform_driver(gadc_thermal_driver);
164
165 MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
166 MODULE_DESCRIPTION("Generic ADC thermal driver using IIO framework with DT");
167 MODULE_LICENSE("GPL v2");
168
