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 	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 
58 static int gadc_thermal_get_temp(void *data, int *temp)
59 {
60 	struct gadc_thermal_info *gti = data;
61 	int val;
62 	int ret;
63 
64 	ret = iio_read_channel_processed(gti->channel, &val);
65 	if (ret < 0) {
66 		dev_err(gti->dev, "IIO channel read failed %d\n", ret);
67 		return ret;
68 	}
69 	*temp = gadc_thermal_adc_to_temp(gti, val);
70 
71 	return 0;
72 }
73 
74 static const struct thermal_zone_of_device_ops gadc_thermal_ops = {
75 	.get_temp = gadc_thermal_get_temp,
76 };
77 
78 static int gadc_thermal_read_linear_lookup_table(struct device *dev,
79 						 struct gadc_thermal_info *gti)
80 {
81 	struct device_node *np = dev->of_node;
82 	int ntable;
83 	int ret;
84 
85 	ntable = of_property_count_elems_of_size(np, "temperature-lookup-table",
86 						 sizeof(u32));
87 	if (ntable <= 0) {
88 		dev_notice(dev, "no lookup table, assuming DAC channel returns milliCelcius\n");
89 		return 0;
90 	}
91 
92 	if (ntable % 2) {
93 		dev_err(dev, "Pair of temperature vs ADC read value missing\n");
94 		return -EINVAL;
95 	}
96 
97 	gti->lookup_table = devm_kcalloc(dev,
98 					 ntable, sizeof(*gti->lookup_table),
99 					 GFP_KERNEL);
100 	if (!gti->lookup_table)
101 		return -ENOMEM;
102 
103 	ret = of_property_read_u32_array(np, "temperature-lookup-table",
104 					 (u32 *)gti->lookup_table, ntable);
105 	if (ret < 0) {
106 		dev_err(dev, "Failed to read temperature lookup table: %d\n",
107 			ret);
108 		return ret;
109 	}
110 
111 	gti->nlookup_table = ntable / 2;
112 
113 	return 0;
114 }
115 
116 static int gadc_thermal_probe(struct platform_device *pdev)
117 {
118 	struct gadc_thermal_info *gti;
119 	int ret;
120 
121 	if (!pdev->dev.of_node) {
122 		dev_err(&pdev->dev, "Only DT based supported\n");
123 		return -ENODEV;
124 	}
125 
126 	gti = devm_kzalloc(&pdev->dev, sizeof(*gti), GFP_KERNEL);
127 	if (!gti)
128 		return -ENOMEM;
129 
130 	ret = gadc_thermal_read_linear_lookup_table(&pdev->dev, gti);
131 	if (ret < 0)
132 		return ret;
133 
134 	gti->dev = &pdev->dev;
135 	platform_set_drvdata(pdev, gti);
136 
137 	gti->channel = devm_iio_channel_get(&pdev->dev, "sensor-channel");
138 	if (IS_ERR(gti->channel)) {
139 		ret = PTR_ERR(gti->channel);
140 		dev_err(&pdev->dev, "IIO channel not found: %d\n", ret);
141 		return ret;
142 	}
143 
144 	gti->tz_dev = devm_thermal_zone_of_sensor_register(&pdev->dev, 0, gti,
145 							   &gadc_thermal_ops);
146 	if (IS_ERR(gti->tz_dev)) {
147 		ret = PTR_ERR(gti->tz_dev);
148 		dev_err(&pdev->dev, "Thermal zone sensor register failed: %d\n",
149 			ret);
150 		return ret;
151 	}
152 
153 	return 0;
154 }
155 
156 static const struct of_device_id of_adc_thermal_match[] = {
157 	{ .compatible = "generic-adc-thermal", },
158 	{},
159 };
160 MODULE_DEVICE_TABLE(of, of_adc_thermal_match);
161 
162 static struct platform_driver gadc_thermal_driver = {
163 	.driver = {
164 		.name = "generic-adc-thermal",
165 		.of_match_table = of_adc_thermal_match,
166 	},
167 	.probe = gadc_thermal_probe,
168 };
169 
170 module_platform_driver(gadc_thermal_driver);
171 
172 MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
173 MODULE_DESCRIPTION("Generic ADC thermal driver using IIO framework with DT");
174 MODULE_LICENSE("GPL v2");
175