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
 16struct 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
 24static 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
 55static int gadc_thermal_get_temp(struct thermal_zone_device *tz, int *temp)
 56{
 57	struct gadc_thermal_info *gti = tz->devdata;
 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
 71static const struct thermal_zone_device_ops gadc_thermal_ops = {
 72	.get_temp = gadc_thermal_get_temp,
 73};
 74
 75static 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
117static 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_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	return 0;
158}
159
160static const struct of_device_id of_adc_thermal_match[] = {
161	{ .compatible = "generic-adc-thermal", },
162	{},
163};
164MODULE_DEVICE_TABLE(of, of_adc_thermal_match);
165
166static 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
174module_platform_driver(gadc_thermal_driver);
175
176MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
177MODULE_DESCRIPTION("Generic ADC thermal driver using IIO framework with DT");
178MODULE_LICENSE("GPL v2");