1/*
  2 * Generic ADC thermal driver
  3 *
  4 * Copyright (C) 2016 NVIDIA CORPORATION. All rights reserved.
  5 *
  6 * Author: Laxman Dewangan <ldewangan@nvidia.com>
  7 *
  8 * This program is free software; you can redistribute it and/or modify
  9 * it under the terms of the GNU General Public License version 2 as
 10 * published by the Free Software Foundation.
 11 */
 12#include <linux/iio/consumer.h>
 13#include <linux/kernel.h>
 14#include <linux/module.h>
 15#include <linux/platform_device.h>
 16#include <linux/slab.h>
 17#include <linux/thermal.h>
 18
 19struct gadc_thermal_info {
 20	struct device *dev;
 21	struct thermal_zone_device *tz_dev;
 22	struct iio_channel *channel;
 23	s32 *lookup_table;
 24	int nlookup_table;
 25};
 26
 27static int gadc_thermal_adc_to_temp(struct gadc_thermal_info *gti, int val)
 28{
 29	int temp, adc_hi, adc_lo;
 30	int i;
 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 - 1)) {
 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		temp = gti->lookup_table[2 * i];
 45		temp -= ((val - adc_lo) * 1000) / (adc_hi - adc_lo);
 46	}
 47
 48	return temp;
 49}
 50
 51static int gadc_thermal_get_temp(void *data, int *temp)
 52{
 53	struct gadc_thermal_info *gti = data;
 54	int val;
 55	int ret;
 56
 57	ret = iio_read_channel_processed(gti->channel, &val);
 58	if (ret < 0) {
 59		dev_err(gti->dev, "IIO channel read failed %d\n", ret);
 60		return ret;
 61	}
 62	*temp = gadc_thermal_adc_to_temp(gti, val);
 63
 64	return 0;
 65}
 66
 67static const struct thermal_zone_of_device_ops gadc_thermal_ops = {
 68	.get_temp = gadc_thermal_get_temp,
 69};
 70
 71static int gadc_thermal_read_linear_lookup_table(struct device *dev,
 72						 struct gadc_thermal_info *gti)
 73{
 74	struct device_node *np = dev->of_node;
 75	int ntable;
 76	int ret;
 77
 78	ntable = of_property_count_elems_of_size(np, "temperature-lookup-table",
 79						 sizeof(u32));
 80	if (ntable < 0) {
 81		dev_err(dev, "Lookup table is not provided\n");
 82		return ntable;
 83	}
 84
 85	if (ntable % 2) {
 86		dev_err(dev, "Pair of temperature vs ADC read value missing\n");
 87		return -EINVAL;
 88	}
 89
 90	gti->lookup_table = devm_kzalloc(dev, sizeof(*gti->lookup_table) *
 91					 ntable, GFP_KERNEL);
 92	if (!gti->lookup_table)
 93		return -ENOMEM;
 94
 95	ret = of_property_read_u32_array(np, "temperature-lookup-table",
 96					 (u32 *)gti->lookup_table, ntable);
 97	if (ret < 0) {
 98		dev_err(dev, "Failed to read temperature lookup table: %d\n",
 99			ret);
100		return ret;
101	}
102
103	gti->nlookup_table = ntable / 2;
104
105	return 0;
106}
107
108static int gadc_thermal_probe(struct platform_device *pdev)
109{
110	struct gadc_thermal_info *gti;
111	int ret;
112
113	if (!pdev->dev.of_node) {
114		dev_err(&pdev->dev, "Only DT based supported\n");
115		return -ENODEV;
116	}
117
118	gti = devm_kzalloc(&pdev->dev, sizeof(*gti), GFP_KERNEL);
119	if (!gti)
120		return -ENOMEM;
121
122	ret = gadc_thermal_read_linear_lookup_table(&pdev->dev, gti);
123	if (ret < 0)
124		return ret;
125
126	gti->dev = &pdev->dev;
127	platform_set_drvdata(pdev, gti);
128
129	gti->channel = devm_iio_channel_get(&pdev->dev, "sensor-channel");
130	if (IS_ERR(gti->channel)) {
131		ret = PTR_ERR(gti->channel);
132		dev_err(&pdev->dev, "IIO channel not found: %d\n", ret);
133		return ret;
134	}
135
136	gti->tz_dev = devm_thermal_zone_of_sensor_register(&pdev->dev, 0, gti,
137							   &gadc_thermal_ops);
138	if (IS_ERR(gti->tz_dev)) {
139		ret = PTR_ERR(gti->tz_dev);
140		dev_err(&pdev->dev, "Thermal zone sensor register failed: %d\n",
141			ret);
142		return ret;
143	}
144
145	return 0;
146}
147
148static const struct of_device_id of_adc_thermal_match[] = {
149	{ .compatible = "generic-adc-thermal", },
150	{},
151};
152MODULE_DEVICE_TABLE(of, of_adc_thermal_match);
153
154static struct platform_driver gadc_thermal_driver = {
155	.driver = {
156		.name = "generic-adc-thermal",
157		.of_match_table = of_adc_thermal_match,
158	},
159	.probe = gadc_thermal_probe,
160};
161
162module_platform_driver(gadc_thermal_driver);
163
164MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
165MODULE_DESCRIPTION("Generic ADC thermal driver using IIO framework with DT");
166MODULE_LICENSE("GPL v2");