linux/drivers/thermal/thermal-generic-adc.c
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   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(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
  71static const struct thermal_zone_of_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_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
 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");
 179