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(struct thermal_zone_device *tz, int *temp)
  56 {
  57         struct gadc_thermal_info *gti = thermal_zone_device_priv(tz);
  58         int val;
  59         int ret;
  60
  61         ret = iio_read_channel_processed(gti->channel, &val);
  62         if (ret < 0)
  63                 return ret;
  64
  65         *temp = gadc_thermal_adc_to_temp(gti, val);
  66
  67         return 0;
  68 }
  69
  70 static const struct thermal_zone_device_ops gadc_thermal_ops = {
  71         .get_temp = gadc_thermal_get_temp,
  72 };
  73
  74 static int gadc_thermal_read_linear_lookup_table(struct device *dev,
  75                                                  struct gadc_thermal_info *gti)
  76 {
  77         struct device_node *np = dev->of_node;
  78         enum iio_chan_type chan_type;
  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                 ret = iio_get_channel_type(gti->channel, &chan_type);
  86                 if (ret || chan_type != IIO_TEMP)
  87                         dev_notice(dev,
  88                                    "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         gti->channel = devm_iio_channel_get(&pdev->dev, "sensor-channel");
 131         if (IS_ERR(gti->channel)) {
 132                 ret = PTR_ERR(gti->channel);
 133                 if (ret != -EPROBE_DEFER)
 134                         dev_err(&pdev->dev, "IIO channel not found: %d\n", ret);
 135                 return ret;
 136         }
 137
 138         ret = gadc_thermal_read_linear_lookup_table(&pdev->dev, gti);
 139         if (ret < 0)
 140                 return ret;
 141
 142         gti->dev = &pdev->dev;
 143         platform_set_drvdata(pdev, gti);
 144
 145         gti->tz_dev = devm_thermal_of_zone_register(&pdev->dev, 0, gti,
 146                                                     &gadc_thermal_ops);
 147         if (IS_ERR(gti->tz_dev)) {
 148                 ret = PTR_ERR(gti->tz_dev);
 149                 if (ret != -EPROBE_DEFER)
 150                         dev_err(&pdev->dev,
 151                                 "Thermal zone sensor register failed: %d\n",
 152                                 ret);
 153                 return ret;
 154         }
 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");