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
18struct 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
26static 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
57static 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
72static const struct thermal_zone_device_ops gadc_thermal_ops = {
73	.get_temp = gadc_thermal_get_temp,
74};
75
76static 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
118static 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
146	gti->tz_dev = devm_thermal_of_zone_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	devm_thermal_add_hwmon_sysfs(&pdev->dev, gti->tz_dev);
158
159	return 0;
160}
161
162static const struct of_device_id of_adc_thermal_match[] = {
163	{ .compatible = "generic-adc-thermal", },
164	{},
165};
166MODULE_DEVICE_TABLE(of, of_adc_thermal_match);
167
168static struct platform_driver gadc_thermal_driver = {
169	.driver = {
170		.name = "generic-adc-thermal",
171		.of_match_table = of_adc_thermal_match,
172	},
173	.probe = gadc_thermal_probe,
174};
175
176module_platform_driver(gadc_thermal_driver);
177
178MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
179MODULE_DESCRIPTION("Generic ADC thermal driver using IIO framework with DT");
180MODULE_LICENSE("GPL v2");
181