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 struct gadc_thermal_info {
17 	struct device *dev;
18 	struct thermal_zone_device *tz_dev;
19 	struct iio_channel *channel;
20 	s32 *lookup_table;
21 	int nlookup_table;
22 };
23 
24 static int gadc_thermal_adc_to_temp(struct gadc_thermal_info *gti, int val)
25 {
26 	int temp, temp_hi, temp_lo, adc_hi, adc_lo;
27 	int i;
28 
29 	if (!gti->lookup_table)
30 		return val;
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 	enum iio_chan_type chan_type;
80 	int ntable;
81 	int ret;
82 
83 	ntable = of_property_count_elems_of_size(np, "temperature-lookup-table",
84 						 sizeof(u32));
85 	if (ntable <= 0) {
86 		ret = iio_get_channel_type(gti->channel, &chan_type);
87 		if (ret || chan_type != IIO_TEMP)
88 			dev_notice(dev,
89 				   "no lookup table, assuming DAC channel returns milliCelcius\n");
90 		return 0;
91 	}
92 
93 	if (ntable % 2) {
94 		dev_err(dev, "Pair of temperature vs ADC read value missing\n");
95 		return -EINVAL;
96 	}
97 
98 	gti->lookup_table = devm_kcalloc(dev,
99 					 ntable, sizeof(*gti->lookup_table),
100 					 GFP_KERNEL);
101 	if (!gti->lookup_table)
102 		return -ENOMEM;
103 
104 	ret = of_property_read_u32_array(np, "temperature-lookup-table",
105 					 (u32 *)gti->lookup_table, ntable);
106 	if (ret < 0) {
107 		dev_err(dev, "Failed to read temperature lookup table: %d\n",
108 			ret);
109 		return ret;
110 	}
111 
112 	gti->nlookup_table = ntable / 2;
113 
114 	return 0;
115 }
116 
117 static int gadc_thermal_probe(struct platform_device *pdev)
118 {
119 	struct gadc_thermal_info *gti;
120 	int ret;
121 
122 	if (!pdev->dev.of_node) {
123 		dev_err(&pdev->dev, "Only DT based supported\n");
124 		return -ENODEV;
125 	}
126 
127 	gti = devm_kzalloc(&pdev->dev, sizeof(*gti), GFP_KERNEL);
128 	if (!gti)
129 		return -ENOMEM;
130 
131 	gti->channel = devm_iio_channel_get(&pdev->dev, "sensor-channel");
132 	if (IS_ERR(gti->channel)) {
133 		ret = PTR_ERR(gti->channel);
134 		if (ret != -EPROBE_DEFER)
135 			dev_err(&pdev->dev, "IIO channel not found: %d\n", ret);
136 		return ret;
137 	}
138 
139 	ret = gadc_thermal_read_linear_lookup_table(&pdev->dev, gti);
140 	if (ret < 0)
141 		return ret;
142 
143 	gti->dev = &pdev->dev;
144 	platform_set_drvdata(pdev, gti);
145 
146 	gti->tz_dev = devm_thermal_zone_of_sensor_register(&pdev->dev, 0, gti,
147 							   &gadc_thermal_ops);
148 	if (IS_ERR(gti->tz_dev)) {
149 		ret = PTR_ERR(gti->tz_dev);
150 		if (ret != -EPROBE_DEFER)
151 			dev_err(&pdev->dev,
152 				"Thermal zone sensor register failed: %d\n",
153 				ret);
154 		return ret;
155 	}
156 
157 	return 0;
158 }
159 
160 static const struct of_device_id of_adc_thermal_match[] = {
161 	{ .compatible = "generic-adc-thermal", },
162 	{},
163 };
164 MODULE_DEVICE_TABLE(of, of_adc_thermal_match);
165 
166 static struct platform_driver gadc_thermal_driver = {
167 	.driver = {
168 		.name = "generic-adc-thermal",
169 		.of_match_table = of_adc_thermal_match,
170 	},
171 	.probe = gadc_thermal_probe,
172 };
173 
174 module_platform_driver(gadc_thermal_driver);
175 
176 MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
177 MODULE_DESCRIPTION("Generic ADC thermal driver using IIO framework with DT");
178 MODULE_LICENSE("GPL v2");
179