drivers/thermal/thermal-generic-adc.c

   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 struct 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
  24 static 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
  55 static 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
  71 static const struct thermal_zone_of_device_ops gadc_thermal_ops = {
  72         .get_temp = gadc_thermal_get_temp,
  73 };
  74
  75 static 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         int ntable;
  80         int ret;
  81
  82         ntable = of_property_count_elems_of_size(np, "temperature-lookup-table",
  83                                                  sizeof(u32));
  84         if (ntable <= 0) {
  85                 dev_notice(dev, "no lookup table, assuming DAC channel returns milliCelcius\n");
  86                 return 0;
  87         }
  88
  89         if (ntable % 2) {
  90                 dev_err(dev, "Pair of temperature vs ADC read value missing\n");
  91                 return -EINVAL;
  92         }
  93
  94         gti->lookup_table = devm_kcalloc(dev,
  95                                          ntable, sizeof(*gti->lookup_table),
  96                                          GFP_KERNEL);
  97         if (!gti->lookup_table)
  98                 return -ENOMEM;
  99
 100         ret = of_property_read_u32_array(np, "temperature-lookup-table",
 101                                          (u32 *)gti->lookup_table, ntable);
 102         if (ret < 0) {
 103                 dev_err(dev, "Failed to read temperature lookup table: %d\n",
 104                         ret);
 105                 return ret;
 106         }
 107
 108         gti->nlookup_table = ntable / 2;
 109
 110         return 0;
 111 }
 112
 113 static int gadc_thermal_probe(struct platform_device *pdev)
 114 {
 115         struct gadc_thermal_info *gti;
 116         int ret;
 117
 118         if (!pdev->dev.of_node) {
 119                 dev_err(&pdev->dev, "Only DT based supported\n");
 120                 return -ENODEV;
 121         }
 122
 123         gti = devm_kzalloc(&pdev->dev, sizeof(*gti), GFP_KERNEL);
 124         if (!gti)
 125                 return -ENOMEM;
 126
 127         ret = gadc_thermal_read_linear_lookup_table(&pdev->dev, gti);
 128         if (ret < 0)
 129                 return ret;
 130
 131         gti->dev = &pdev->dev;
 132         platform_set_drvdata(pdev, gti);
 133
 134         gti->channel = devm_iio_channel_get(&pdev->dev, "sensor-channel");
 135         if (IS_ERR(gti->channel)) {
 136                 ret = PTR_ERR(gti->channel);
 137                 dev_err(&pdev->dev, "IIO channel not found: %d\n", ret);
 138                 return ret;
 139         }
 140
 141         gti->tz_dev = devm_thermal_zone_of_sensor_register(&pdev->dev, 0, gti,
 142                                                            &gadc_thermal_ops);
 143         if (IS_ERR(gti->tz_dev)) {
 144                 ret = PTR_ERR(gti->tz_dev);
 145                 dev_err(&pdev->dev, "Thermal zone sensor register failed: %d\n",
 146                         ret);
 147                 return ret;
 148         }
 149
 150         return 0;
 151 }
 152
 153 static const struct of_device_id of_adc_thermal_match[] = {
 154         { .compatible = "generic-adc-thermal", },
 155         {},
 156 };
 157 MODULE_DEVICE_TABLE(of, of_adc_thermal_match);
 158
 159 static struct platform_driver gadc_thermal_driver = {
 160         .driver = {
 161                 .name = "generic-adc-thermal",
 162                 .of_match_table = of_adc_thermal_match,
 163         },
 164         .probe = gadc_thermal_probe,
 165 };
 166
 167 module_platform_driver(gadc_thermal_driver);
 168
 169 MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
 170 MODULE_DESCRIPTION("Generic ADC thermal driver using IIO framework with DT");
 171 MODULE_LICENSE("GPL v2");