drivers/thermal/thermal-generic-adc.c

   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
  19 struct 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
  27 static int gadc_thermal_adc_to_temp(struct gadc_thermal_info *gti, int val)
  28 {
  29         int temp, temp_hi, temp_lo, 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) {
  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_err(dev, "Lookup table is not provided\n");
  86                 return ntable;
  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_kzalloc(dev, sizeof(*gti->lookup_table) *
  95                                          ntable, GFP_KERNEL);
  96         if (!gti->lookup_table)
  97                 return -ENOMEM;
  98
  99         ret = of_property_read_u32_array(np, "temperature-lookup-table",
 100                                          (u32 *)gti->lookup_table, ntable);
 101         if (ret < 0) {
 102                 dev_err(dev, "Failed to read temperature lookup table: %d\n",
 103                         ret);
 104                 return ret;
 105         }
 106
 107         gti->nlookup_table = ntable / 2;
 108
 109         return 0;
 110 }
 111
 112 static int gadc_thermal_probe(struct platform_device *pdev)
 113 {
 114         struct gadc_thermal_info *gti;
 115         int ret;
 116
 117         if (!pdev->dev.of_node) {
 118                 dev_err(&pdev->dev, "Only DT based supported\n");
 119                 return -ENODEV;
 120         }
 121
 122         gti = devm_kzalloc(&pdev->dev, sizeof(*gti), GFP_KERNEL);
 123         if (!gti)
 124                 return -ENOMEM;
 125
 126         ret = gadc_thermal_read_linear_lookup_table(&pdev->dev, gti);
 127         if (ret < 0)
 128                 return ret;
 129
 130         gti->dev = &pdev->dev;
 131         platform_set_drvdata(pdev, gti);
 132
 133         gti->channel = iio_channel_get(&pdev->dev, "sensor-channel");
 134         if (IS_ERR(gti->channel)) {
 135                 ret = PTR_ERR(gti->channel);
 136                 dev_err(&pdev->dev, "IIO channel not found: %d\n", ret);
 137                 return ret;
 138         }
 139
 140         gti->tz_dev = thermal_zone_of_sensor_register(&pdev->dev, 0,
 141                                                       gti, &gadc_thermal_ops);
 142         if (IS_ERR(gti->tz_dev)) {
 143                 ret = PTR_ERR(gti->tz_dev);
 144                 dev_err(&pdev->dev, "Thermal zone sensor register failed: %d\n",
 145                         ret);
 146                 goto sensor_fail;
 147         }
 148
 149         return 0;
 150
 151 sensor_fail:
 152         iio_channel_release(gti->channel);
 153
 154         return ret;
 155 }
 156
 157 static int gadc_thermal_remove(struct platform_device *pdev)
 158 {
 159         struct gadc_thermal_info *gti = platform_get_drvdata(pdev);
 160
 161         thermal_zone_of_sensor_unregister(&pdev->dev, gti->tz_dev);
 162         iio_channel_release(gti->channel);
 163
 164         return 0;
 165 }
 166
 167 static const struct of_device_id of_adc_thermal_match[] = {
 168         { .compatible = "generic-adc-thermal", },
 169         {},
 170 };
 171 MODULE_DEVICE_TABLE(of, of_adc_thermal_match);
 172
 173 static struct platform_driver gadc_thermal_driver = {
 174         .driver = {
 175                 .name = "generic-adc-thermal",
 176                 .of_match_table = of_adc_thermal_match,
 177         },
 178         .probe = gadc_thermal_probe,
 179         .remove = gadc_thermal_remove,
 180 };
 181
 182 module_platform_driver(gadc_thermal_driver);
 183
 184 MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
 185 MODULE_DESCRIPTION("Generic ADC thermal driver using IIO framework with DT");
 186 MODULE_LICENSE("GPL v2");