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(struct thermal_zone_device *tz, int *temp)
56 {
57 	struct gadc_thermal_info *gti = thermal_zone_device_priv(tz);
58 	int val;
59 	int ret;
60 
61 	ret = iio_read_channel_processed(gti->channel, &val);
62 	if (ret < 0)
63 		return ret;
64 
65 	*temp = gadc_thermal_adc_to_temp(gti, val);
66 
67 	return 0;
68 }
69 
70 static const struct thermal_zone_device_ops gadc_thermal_ops = {
71 	.get_temp = gadc_thermal_get_temp,
72 };
73 
74 static int gadc_thermal_read_linear_lookup_table(struct device *dev,
75 						 struct gadc_thermal_info *gti)
76 {
77 	struct device_node *np = dev->of_node;
78 	enum iio_chan_type chan_type;
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 		ret = iio_get_channel_type(gti->channel, &chan_type);
86 		if (ret || chan_type != IIO_TEMP)
87 			dev_notice(dev,
88 				   "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 	gti->channel = devm_iio_channel_get(&pdev->dev, "sensor-channel");
131 	if (IS_ERR(gti->channel)) {
132 		ret = PTR_ERR(gti->channel);
133 		if (ret != -EPROBE_DEFER)
134 			dev_err(&pdev->dev, "IIO channel not found: %d\n", ret);
135 		return ret;
136 	}
137 
138 	ret = gadc_thermal_read_linear_lookup_table(&pdev->dev, gti);
139 	if (ret < 0)
140 		return ret;
141 
142 	gti->dev = &pdev->dev;
143 	platform_set_drvdata(pdev, gti);
144 
145 	gti->tz_dev = devm_thermal_of_zone_register(&pdev->dev, 0, gti,
146 						    &gadc_thermal_ops);
147 	if (IS_ERR(gti->tz_dev)) {
148 		ret = PTR_ERR(gti->tz_dev);
149 		if (ret != -EPROBE_DEFER)
150 			dev_err(&pdev->dev,
151 				"Thermal zone sensor register failed: %d\n",
152 				ret);
153 		return ret;
154 	}
155 
156 	return 0;
157 }
158 
159 static const struct of_device_id of_adc_thermal_match[] = {
160 	{ .compatible = "generic-adc-thermal", },
161 	{},
162 };
163 MODULE_DEVICE_TABLE(of, of_adc_thermal_match);
164 
165 static struct platform_driver gadc_thermal_driver = {
166 	.driver = {
167 		.name = "generic-adc-thermal",
168 		.of_match_table = of_adc_thermal_match,
169 	},
170 	.probe = gadc_thermal_probe,
171 };
172 
173 module_platform_driver(gadc_thermal_driver);
174 
175 MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
176 MODULE_DESCRIPTION("Generic ADC thermal driver using IIO framework with DT");
177 MODULE_LICENSE("GPL v2");
178