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 #include "thermal_hwmon.h"
  17
  18 struct gadc_thermal_info {
  19         struct device *dev;
  20         struct thermal_zone_device *tz_dev;
  21         struct iio_channel *channel;
  22         s32 *lookup_table;
  23         int nlookup_table;
  24 };
  25
  26 static int gadc_thermal_adc_to_temp(struct gadc_thermal_info *gti, int val)
  27 {
  28         int temp, temp_hi, temp_lo, adc_hi, adc_lo;
  29         int i;
  30
  31         if (!gti->lookup_table)
  32                 return val;
  33
  34         for (i = 0; i < gti->nlookup_table; i++) {
  35                 if (val >= gti->lookup_table[2 * i + 1])
  36                         break;
  37         }
  38
  39         if (i == 0) {
  40                 temp = gti->lookup_table[0];
  41         } else if (i >= gti->nlookup_table) {
  42                 temp = gti->lookup_table[2 * (gti->nlookup_table - 1)];
  43         } else {
  44                 adc_hi = gti->lookup_table[2 * i - 1];
  45                 adc_lo = gti->lookup_table[2 * i + 1];
  46
  47                 temp_hi = gti->lookup_table[2 * i - 2];
  48                 temp_lo = gti->lookup_table[2 * i];
  49
  50                 temp = temp_hi + mult_frac(temp_lo - temp_hi, val - adc_hi,
  51                                            adc_lo - adc_hi);
  52         }
  53
  54         return temp;
  55 }
  56
  57 static int gadc_thermal_get_temp(struct thermal_zone_device *tz, int *temp)
  58 {
  59         struct gadc_thermal_info *gti = thermal_zone_device_priv(tz);
  60         int val;
  61         int ret;
  62
  63         ret = iio_read_channel_processed(gti->channel, &val);
  64         if (ret < 0)
  65                 return ret;
  66
  67         *temp = gadc_thermal_adc_to_temp(gti, val);
  68
  69         return 0;
  70 }
  71
  72 static const struct thermal_zone_device_ops gadc_thermal_ops = {
  73         .get_temp = gadc_thermal_get_temp,
  74 };
  75
  76 static int gadc_thermal_read_linear_lookup_table(struct device *dev,
  77                                                  struct gadc_thermal_info *gti)
  78 {
  79         struct device_node *np = dev->of_node;
  80         enum iio_chan_type chan_type;
  81         int ntable;
  82         int ret;
  83
  84         ntable = of_property_count_elems_of_size(np, "temperature-lookup-table",
  85                                                  sizeof(u32));
  86         if (ntable <= 0) {
  87                 ret = iio_get_channel_type(gti->channel, &chan_type);
  88                 if (ret || chan_type != IIO_TEMP)
  89                         dev_notice(dev,
  90                                    "no lookup table, assuming DAC channel returns milliCelcius\n");
  91                 return 0;
  92         }
  93
  94         if (ntable % 2) {
  95                 dev_err(dev, "Pair of temperature vs ADC read value missing\n");
  96                 return -EINVAL;
  97         }
  98
  99         gti->lookup_table = devm_kcalloc(dev,
 100                                          ntable, sizeof(*gti->lookup_table),
 101                                          GFP_KERNEL);
 102         if (!gti->lookup_table)
 103                 return -ENOMEM;
 104
 105         ret = of_property_read_u32_array(np, "temperature-lookup-table",
 106                                          (u32 *)gti->lookup_table, ntable);
 107         if (ret < 0) {
 108                 dev_err(dev, "Failed to read temperature lookup table: %d\n",
 109                         ret);
 110                 return ret;
 111         }
 112
 113         gti->nlookup_table = ntable / 2;
 114
 115         return 0;
 116 }
 117
 118 static int gadc_thermal_probe(struct platform_device *pdev)
 119 {
 120         struct device *dev = &pdev->dev;
 121         struct gadc_thermal_info *gti;
 122         int ret;
 123
 124         if (!dev->of_node) {
 125                 dev_err(dev, "Only DT based supported\n");
 126                 return -ENODEV;
 127         }
 128
 129         gti = devm_kzalloc(dev, sizeof(*gti), GFP_KERNEL);
 130         if (!gti)
 131                 return -ENOMEM;
 132
 133         gti->channel = devm_iio_channel_get(dev, "sensor-channel");
 134         if (IS_ERR(gti->channel))
 135                 return dev_err_probe(dev, PTR_ERR(gti->channel), "IIO channel not found\n");
 136
 137         ret = gadc_thermal_read_linear_lookup_table(dev, gti);
 138         if (ret < 0)
 139                 return ret;
 140
 141         gti->dev = dev;
 142
 143         gti->tz_dev = devm_thermal_of_zone_register(dev, 0, gti,
 144                                                     &gadc_thermal_ops);
 145         if (IS_ERR(gti->tz_dev)) {
 146                 ret = PTR_ERR(gti->tz_dev);
 147                 if (ret != -EPROBE_DEFER)
 148                         dev_err(dev,
 149                                 "Thermal zone sensor register failed: %d\n",
 150                                 ret);
 151                 return ret;
 152         }
 153
 154         devm_thermal_add_hwmon_sysfs(dev, gti->tz_dev);
 155
 156         return 0;
 157 }
 158
 159 static const struct of_device_id of_adc_thermal_match[] = {
 160         { .compatible = "generic-adc-thermal", },
 161         {},
 162 };
 163 MODULE_DEVICE_TABLE(of, of_adc_thermal_match);
 164
 165 static struct platform_driver gadc_thermal_driver = {
 166         .driver = {
 167                 .name = "generic-adc-thermal",
 168                 .of_match_table = of_adc_thermal_match,
 169         },
 170         .probe = gadc_thermal_probe,
 171 };
 172
 173 module_platform_driver(gadc_thermal_driver);
 174
 175 MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
 176 MODULE_DESCRIPTION("Generic ADC thermal driver using IIO framework with DT");
 177 MODULE_LICENSE("GPL v2");