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 #include "thermal_hwmon.h"
17 
18 struct gadc_thermal_info {
19 	struct device *dev;
20 	struct thermal_zone_device *tz_dev;
21 	struct iio_channel *channel;
22 	s32 *lookup_table;
23 	int nlookup_table;
24 };
25 
26 static int gadc_thermal_adc_to_temp(struct gadc_thermal_info *gti, int val)
27 {
28 	int temp, temp_hi, temp_lo, adc_hi, adc_lo;
29 	int i;
30 
31 	if (!gti->lookup_table)
32 		return val;
33 
34 	for (i = 0; i < gti->nlookup_table; i++) {
35 		if (val >= gti->lookup_table[2 * i + 1])
36 			break;
37 	}
38 
39 	if (i == 0) {
40 		temp = gti->lookup_table[0];
41 	} else if (i >= gti->nlookup_table) {
42 		temp = gti->lookup_table[2 * (gti->nlookup_table - 1)];
43 	} else {
44 		adc_hi = gti->lookup_table[2 * i - 1];
45 		adc_lo = gti->lookup_table[2 * i + 1];
46 
47 		temp_hi = gti->lookup_table[2 * i - 2];
48 		temp_lo = gti->lookup_table[2 * i];
49 
50 		temp = temp_hi + mult_frac(temp_lo - temp_hi, val - adc_hi,
51 					   adc_lo - adc_hi);
52 	}
53 
54 	return temp;
55 }
56 
57 static int gadc_thermal_get_temp(struct thermal_zone_device *tz, int *temp)
58 {
59 	struct gadc_thermal_info *gti = thermal_zone_device_priv(tz);
60 	int val;
61 	int ret;
62 
63 	ret = iio_read_channel_processed(gti->channel, &val);
64 	if (ret < 0)
65 		return ret;
66 
67 	*temp = gadc_thermal_adc_to_temp(gti, val);
68 
69 	return 0;
70 }
71 
72 static const struct thermal_zone_device_ops gadc_thermal_ops = {
73 	.get_temp = gadc_thermal_get_temp,
74 };
75 
76 static int gadc_thermal_read_linear_lookup_table(struct device *dev,
77 						 struct gadc_thermal_info *gti)
78 {
79 	struct device_node *np = dev->of_node;
80 	enum iio_chan_type chan_type;
81 	int ntable;
82 	int ret;
83 
84 	ntable = of_property_count_elems_of_size(np, "temperature-lookup-table",
85 						 sizeof(u32));
86 	if (ntable <= 0) {
87 		ret = iio_get_channel_type(gti->channel, &chan_type);
88 		if (ret || chan_type != IIO_TEMP)
89 			dev_notice(dev,
90 				   "no lookup table, assuming DAC channel returns milliCelcius\n");
91 		return 0;
92 	}
93 
94 	if (ntable % 2) {
95 		dev_err(dev, "Pair of temperature vs ADC read value missing\n");
96 		return -EINVAL;
97 	}
98 
99 	gti->lookup_table = devm_kcalloc(dev,
100 					 ntable, sizeof(*gti->lookup_table),
101 					 GFP_KERNEL);
102 	if (!gti->lookup_table)
103 		return -ENOMEM;
104 
105 	ret = of_property_read_u32_array(np, "temperature-lookup-table",
106 					 (u32 *)gti->lookup_table, ntable);
107 	if (ret < 0) {
108 		dev_err(dev, "Failed to read temperature lookup table: %d\n",
109 			ret);
110 		return ret;
111 	}
112 
113 	gti->nlookup_table = ntable / 2;
114 
115 	return 0;
116 }
117 
118 static int gadc_thermal_probe(struct platform_device *pdev)
119 {
120 	struct gadc_thermal_info *gti;
121 	int ret;
122 
123 	if (!pdev->dev.of_node) {
124 		dev_err(&pdev->dev, "Only DT based supported\n");
125 		return -ENODEV;
126 	}
127 
128 	gti = devm_kzalloc(&pdev->dev, sizeof(*gti), GFP_KERNEL);
129 	if (!gti)
130 		return -ENOMEM;
131 
132 	gti->channel = devm_iio_channel_get(&pdev->dev, "sensor-channel");
133 	if (IS_ERR(gti->channel)) {
134 		ret = PTR_ERR(gti->channel);
135 		if (ret != -EPROBE_DEFER)
136 			dev_err(&pdev->dev, "IIO channel not found: %d\n", ret);
137 		return ret;
138 	}
139 
140 	ret = gadc_thermal_read_linear_lookup_table(&pdev->dev, gti);
141 	if (ret < 0)
142 		return ret;
143 
144 	gti->dev = &pdev->dev;
145 	platform_set_drvdata(pdev, gti);
146 
147 	gti->tz_dev = devm_thermal_of_zone_register(&pdev->dev, 0, gti,
148 						    &gadc_thermal_ops);
149 	if (IS_ERR(gti->tz_dev)) {
150 		ret = PTR_ERR(gti->tz_dev);
151 		if (ret != -EPROBE_DEFER)
152 			dev_err(&pdev->dev,
153 				"Thermal zone sensor register failed: %d\n",
154 				ret);
155 		return ret;
156 	}
157 
158 	devm_thermal_add_hwmon_sysfs(&pdev->dev, gti->tz_dev);
159 
160 	return 0;
161 }
162 
163 static const struct of_device_id of_adc_thermal_match[] = {
164 	{ .compatible = "generic-adc-thermal", },
165 	{},
166 };
167 MODULE_DEVICE_TABLE(of, of_adc_thermal_match);
168 
169 static struct platform_driver gadc_thermal_driver = {
170 	.driver = {
171 		.name = "generic-adc-thermal",
172 		.of_match_table = of_adc_thermal_match,
173 	},
174 	.probe = gadc_thermal_probe,
175 };
176 
177 module_platform_driver(gadc_thermal_driver);
178 
179 MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
180 MODULE_DESCRIPTION("Generic ADC thermal driver using IIO framework with DT");
181 MODULE_LICENSE("GPL v2");
182