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
gadc_thermal_adc_to_temp(struct gadc_thermal_info * gti,int val)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
gadc_thermal_get_temp(void * data,int * temp)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
gadc_thermal_read_linear_lookup_table(struct device * dev,struct gadc_thermal_info * gti)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
gadc_thermal_probe(struct platform_device * pdev)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