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, temp_hi, temp_lo, 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) {
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 
45 		temp_hi = gti->lookup_table[2 * i - 2];
46 		temp_lo = gti->lookup_table[2 * i];
47 
48 		temp = temp_hi + mult_frac(temp_lo - temp_hi, val - adc_hi,
49 					   adc_lo - adc_hi);
50 	}
51 
52 	return temp;
53 }
54 
55 static int gadc_thermal_get_temp(void *data, int *temp)
56 {
57 	struct gadc_thermal_info *gti = data;
58 	int val;
59 	int ret;
60 
61 	ret = iio_read_channel_processed(gti->channel, &val);
62 	if (ret < 0) {
63 		dev_err(gti->dev, "IIO channel read failed %d\n", ret);
64 		return ret;
65 	}
66 	*temp = gadc_thermal_adc_to_temp(gti, val);
67 
68 	return 0;
69 }
70 
71 static const struct thermal_zone_of_device_ops gadc_thermal_ops = {
72 	.get_temp = gadc_thermal_get_temp,
73 };
74 
75 static int gadc_thermal_read_linear_lookup_table(struct device *dev,
76 						 struct gadc_thermal_info *gti)
77 {
78 	struct device_node *np = dev->of_node;
79 	int ntable;
80 	int ret;
81 
82 	ntable = of_property_count_elems_of_size(np, "temperature-lookup-table",
83 						 sizeof(u32));
84 	if (ntable < 0) {
85 		dev_err(dev, "Lookup table is not provided\n");
86 		return ntable;
87 	}
88 
89 	if (ntable % 2) {
90 		dev_err(dev, "Pair of temperature vs ADC read value missing\n");
91 		return -EINVAL;
92 	}
93 
94 	gti->lookup_table = devm_kcalloc(dev,
95 					 ntable, sizeof(*gti->lookup_table),
96 					 GFP_KERNEL);
97 	if (!gti->lookup_table)
98 		return -ENOMEM;
99 
100 	ret = of_property_read_u32_array(np, "temperature-lookup-table",
101 					 (u32 *)gti->lookup_table, ntable);
102 	if (ret < 0) {
103 		dev_err(dev, "Failed to read temperature lookup table: %d\n",
104 			ret);
105 		return ret;
106 	}
107 
108 	gti->nlookup_table = ntable / 2;
109 
110 	return 0;
111 }
112 
113 static int gadc_thermal_probe(struct platform_device *pdev)
114 {
115 	struct gadc_thermal_info *gti;
116 	int ret;
117 
118 	if (!pdev->dev.of_node) {
119 		dev_err(&pdev->dev, "Only DT based supported\n");
120 		return -ENODEV;
121 	}
122 
123 	gti = devm_kzalloc(&pdev->dev, sizeof(*gti), GFP_KERNEL);
124 	if (!gti)
125 		return -ENOMEM;
126 
127 	ret = gadc_thermal_read_linear_lookup_table(&pdev->dev, gti);
128 	if (ret < 0)
129 		return ret;
130 
131 	gti->dev = &pdev->dev;
132 	platform_set_drvdata(pdev, gti);
133 
134 	gti->channel = devm_iio_channel_get(&pdev->dev, "sensor-channel");
135 	if (IS_ERR(gti->channel)) {
136 		ret = PTR_ERR(gti->channel);
137 		dev_err(&pdev->dev, "IIO channel not found: %d\n", ret);
138 		return ret;
139 	}
140 
141 	gti->tz_dev = devm_thermal_zone_of_sensor_register(&pdev->dev, 0, gti,
142 							   &gadc_thermal_ops);
143 	if (IS_ERR(gti->tz_dev)) {
144 		ret = PTR_ERR(gti->tz_dev);
145 		dev_err(&pdev->dev, "Thermal zone sensor register failed: %d\n",
146 			ret);
147 		return ret;
148 	}
149 
150 	return 0;
151 }
152 
153 static const struct of_device_id of_adc_thermal_match[] = {
154 	{ .compatible = "generic-adc-thermal", },
155 	{},
156 };
157 MODULE_DEVICE_TABLE(of, of_adc_thermal_match);
158 
159 static struct platform_driver gadc_thermal_driver = {
160 	.driver = {
161 		.name = "generic-adc-thermal",
162 		.of_match_table = of_adc_thermal_match,
163 	},
164 	.probe = gadc_thermal_probe,
165 };
166 
167 module_platform_driver(gadc_thermal_driver);
168 
169 MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
170 MODULE_DESCRIPTION("Generic ADC thermal driver using IIO framework with DT");
171 MODULE_LICENSE("GPL v2");
172