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         if (!gti->lookup_table)
  33                 return val;
  34
  35         for (i = 0; i < gti->nlookup_table; i++) {
  36                 if (val >= gti->lookup_table[2 * i + 1])
  37                         break;
  38         }
  39
  40         if (i == 0) {
  41                 temp = gti->lookup_table[0];
  42         } else if (i >= gti->nlookup_table) {
  43                 temp = gti->lookup_table[2 * (gti->nlookup_table - 1)];
  44         } else {
  45                 adc_hi = gti->lookup_table[2 * i - 1];
  46                 adc_lo = gti->lookup_table[2 * i + 1];
  47
  48                 temp_hi = gti->lookup_table[2 * i - 2];
  49                 temp_lo = gti->lookup_table[2 * i];
  50
  51                 temp = temp_hi + mult_frac(temp_lo - temp_hi, val - adc_hi,
  52                                            adc_lo - adc_hi);
  53         }
  54
  55         return temp;
  56 }
  57
  58 static int gadc_thermal_get_temp(void *data, int *temp)
  59 {
  60         struct gadc_thermal_info *gti = data;
  61         int val;
  62         int ret;
  63
  64         ret = iio_read_channel_processed(gti->channel, &val);
  65         if (ret < 0) {
  66                 dev_err(gti->dev, "IIO channel read failed %d\n", ret);
  67                 return ret;
  68         }
  69         *temp = gadc_thermal_adc_to_temp(gti, val);
  70
  71         return 0;
  72 }
  73
  74 static const struct thermal_zone_of_device_ops gadc_thermal_ops = {
  75         .get_temp = gadc_thermal_get_temp,
  76 };
  77
  78 static int gadc_thermal_read_linear_lookup_table(struct device *dev,
  79                                                  struct gadc_thermal_info *gti)
  80 {
  81         struct device_node *np = dev->of_node;
  82         int ntable;
  83         int ret;
  84
  85         ntable = of_property_count_elems_of_size(np, "temperature-lookup-table",
  86                                                  sizeof(u32));
  87         if (ntable <= 0) {
  88                 dev_notice(dev, "no lookup table, assuming DAC channel returns milliCelcius\n");
  89                 return 0;
  90         }
  91
  92         if (ntable % 2) {
  93                 dev_err(dev, "Pair of temperature vs ADC read value missing\n");
  94                 return -EINVAL;
  95         }
  96
  97         gti->lookup_table = devm_kcalloc(dev,
  98                                          ntable, sizeof(*gti->lookup_table),
  99                                          GFP_KERNEL);
 100         if (!gti->lookup_table)
 101                 return -ENOMEM;
 102
 103         ret = of_property_read_u32_array(np, "temperature-lookup-table",
 104                                          (u32 *)gti->lookup_table, ntable);
 105         if (ret < 0) {
 106                 dev_err(dev, "Failed to read temperature lookup table: %d\n",
 107                         ret);
 108                 return ret;
 109         }
 110
 111         gti->nlookup_table = ntable / 2;
 112
 113         return 0;
 114 }
 115
 116 static int gadc_thermal_probe(struct platform_device *pdev)
 117 {
 118         struct gadc_thermal_info *gti;
 119         int ret;
 120
 121         if (!pdev->dev.of_node) {
 122                 dev_err(&pdev->dev, "Only DT based supported\n");
 123                 return -ENODEV;
 124         }
 125
 126         gti = devm_kzalloc(&pdev->dev, sizeof(*gti), GFP_KERNEL);
 127         if (!gti)
 128                 return -ENOMEM;
 129
 130         ret = gadc_thermal_read_linear_lookup_table(&pdev->dev, gti);
 131         if (ret < 0)
 132                 return ret;
 133
 134         gti->dev = &pdev->dev;
 135         platform_set_drvdata(pdev, gti);
 136
 137         gti->channel = devm_iio_channel_get(&pdev->dev, "sensor-channel");
 138         if (IS_ERR(gti->channel)) {
 139                 ret = PTR_ERR(gti->channel);
 140                 dev_err(&pdev->dev, "IIO channel not found: %d\n", ret);
 141                 return ret;
 142         }
 143
 144         gti->tz_dev = devm_thermal_zone_of_sensor_register(&pdev->dev, 0, gti,
 145                                                            &gadc_thermal_ops);
 146         if (IS_ERR(gti->tz_dev)) {
 147                 ret = PTR_ERR(gti->tz_dev);
 148                 dev_err(&pdev->dev, "Thermal zone sensor register failed: %d\n",
 149                         ret);
 150                 return ret;
 151         }
 152
 153         return 0;
 154 }
 155
 156 static const struct of_device_id of_adc_thermal_match[] = {
 157         { .compatible = "generic-adc-thermal", },
 158         {},
 159 };
 160 MODULE_DEVICE_TABLE(of, of_adc_thermal_match);
 161
 162 static struct platform_driver gadc_thermal_driver = {
 163         .driver = {
 164                 .name = "generic-adc-thermal",
 165                 .of_match_table = of_adc_thermal_match,
 166         },
 167         .probe = gadc_thermal_probe,
 168 };
 169
 170 module_platform_driver(gadc_thermal_driver);
 171
 172 MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
 173 MODULE_DESCRIPTION("Generic ADC thermal driver using IIO framework with DT");
 174 MODULE_LICENSE("GPL v2");