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 device *dev = &pdev->dev;
121	struct gadc_thermal_info *gti;
122	int ret;
123
124	if (!dev->of_node) {
125		dev_err(dev, "Only DT based supported\n");
126		return -ENODEV;
127	}
128
129	gti = devm_kzalloc(dev, sizeof(*gti), GFP_KERNEL);
130	if (!gti)
131		return -ENOMEM;
132
133	gti->channel = devm_iio_channel_get(dev, "sensor-channel");
134	if (IS_ERR(gti->channel))
135		return dev_err_probe(dev, PTR_ERR(gti->channel), "IIO channel not found\n");
136
137	ret = gadc_thermal_read_linear_lookup_table(dev, gti);
138	if (ret < 0)
139		return ret;
140
141	gti->dev = dev;
142
143	gti->tz_dev = devm_thermal_of_zone_register(dev, 0, gti,
144						    &gadc_thermal_ops);
145	if (IS_ERR(gti->tz_dev)) {
146		ret = PTR_ERR(gti->tz_dev);
147		if (ret != -EPROBE_DEFER)
148			dev_err(dev,
149				"Thermal zone sensor register failed: %d\n",
150				ret);
151		return ret;
152	}
153
154	devm_thermal_add_hwmon_sysfs(dev, gti->tz_dev);
155
156	return 0;
157}
158
159static const struct of_device_id of_adc_thermal_match[] = {
160	{ .compatible = "generic-adc-thermal", },
161	{},
162};
163MODULE_DEVICE_TABLE(of, of_adc_thermal_match);
164
165static struct platform_driver gadc_thermal_driver = {
166	.driver = {
167		.name = "generic-adc-thermal",
168		.of_match_table = of_adc_thermal_match,
169	},
170	.probe = gadc_thermal_probe,
171};
172
173module_platform_driver(gadc_thermal_driver);
174
175MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
176MODULE_DESCRIPTION("Generic ADC thermal driver using IIO framework with DT");
177MODULE_LICENSE("GPL v2");