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 
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 
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 
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_kzalloc(dev, sizeof(*gti->lookup_table) *
91 					 ntable, GFP_KERNEL);
92 	if (!gti->lookup_table)
93 		return -ENOMEM;
94 
95 	ret = of_property_read_u32_array(np, "temperature-lookup-table",
96 					 (u32 *)gti->lookup_table, ntable);
97 	if (ret < 0) {
98 		dev_err(dev, "Failed to read temperature lookup table: %d\n",
99 			ret);
100 		return ret;
101 	}
102 
103 	gti->nlookup_table = ntable / 2;
104 
105 	return 0;
106 }
107 
108 static int gadc_thermal_probe(struct platform_device *pdev)
109 {
110 	struct gadc_thermal_info *gti;
111 	int ret;
112 
113 	if (!pdev->dev.of_node) {
114 		dev_err(&pdev->dev, "Only DT based supported\n");
115 		return -ENODEV;
116 	}
117 
118 	gti = devm_kzalloc(&pdev->dev, sizeof(*gti), GFP_KERNEL);
119 	if (!gti)
120 		return -ENOMEM;
121 
122 	ret = gadc_thermal_read_linear_lookup_table(&pdev->dev, gti);
123 	if (ret < 0)
124 		return ret;
125 
126 	gti->dev = &pdev->dev;
127 	platform_set_drvdata(pdev, gti);
128 
129 	gti->channel = devm_iio_channel_get(&pdev->dev, "sensor-channel");
130 	if (IS_ERR(gti->channel)) {
131 		ret = PTR_ERR(gti->channel);
132 		dev_err(&pdev->dev, "IIO channel not found: %d\n", ret);
133 		return ret;
134 	}
135 
136 	gti->tz_dev = devm_thermal_zone_of_sensor_register(&pdev->dev, 0, gti,
137 							   &gadc_thermal_ops);
138 	if (IS_ERR(gti->tz_dev)) {
139 		ret = PTR_ERR(gti->tz_dev);
140 		dev_err(&pdev->dev, "Thermal zone sensor register failed: %d\n",
141 			ret);
142 		return ret;
143 	}
144 
145 	return 0;
146 }
147 
148 static const struct of_device_id of_adc_thermal_match[] = {
149 	{ .compatible = "generic-adc-thermal", },
150 	{},
151 };
152 MODULE_DEVICE_TABLE(of, of_adc_thermal_match);
153 
154 static struct platform_driver gadc_thermal_driver = {
155 	.driver = {
156 		.name = "generic-adc-thermal",
157 		.of_match_table = of_adc_thermal_match,
158 	},
159 	.probe = gadc_thermal_probe,
160 };
161 
162 module_platform_driver(gadc_thermal_driver);
163 
164 MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
165 MODULE_DESCRIPTION("Generic ADC thermal driver using IIO framework with DT");
166 MODULE_LICENSE("GPL v2");
167