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 <[email protected]>
   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, 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
  51 static 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
  67 static const struct thermal_zone_of_device_ops gadc_thermal_ops = {
  68         .get_temp = gadc_thermal_get_temp,
  69 };
  70
  71 static 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
 108 static 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
 148 static const struct of_device_id of_adc_thermal_match[] = {
 149         { .compatible = "generic-adc-thermal", },
 150         {},
 151 };
 152 MODULE_DEVICE_TABLE(of, of_adc_thermal_match);
 153
 154 static 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
 162 module_platform_driver(gadc_thermal_driver);
 163
 164 MODULE_AUTHOR("Laxman Dewangan <[email protected]>");
 165 MODULE_DESCRIPTION("Generic ADC thermal driver using IIO framework with DT");
 166 MODULE_LICENSE("GPL v2");