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, 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_kcalloc(dev, 91 ntable, sizeof(*gti->lookup_table), 92 GFP_KERNEL); 93 if (!gti->lookup_table) 94 return -ENOMEM; 95 96 ret = of_property_read_u32_array(np, "temperature-lookup-table", 97 (u32 *)gti->lookup_table, ntable); 98 if (ret < 0) { 99 dev_err(dev, "Failed to read temperature lookup table: %d\n", 100 ret); 101 return ret; 102 } 103 104 gti->nlookup_table = ntable / 2; 105 106 return 0; 107 } 108 109 static int gadc_thermal_probe(struct platform_device *pdev) 110 { 111 struct gadc_thermal_info *gti; 112 int ret; 113 114 if (!pdev->dev.of_node) { 115 dev_err(&pdev->dev, "Only DT based supported\n"); 116 return -ENODEV; 117 } 118 119 gti = devm_kzalloc(&pdev->dev, sizeof(*gti), GFP_KERNEL); 120 if (!gti) 121 return -ENOMEM; 122 123 ret = gadc_thermal_read_linear_lookup_table(&pdev->dev, gti); 124 if (ret < 0) 125 return ret; 126 127 gti->dev = &pdev->dev; 128 platform_set_drvdata(pdev, gti); 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 dev_err(&pdev->dev, "IIO channel not found: %d\n", ret); 134 return ret; 135 } 136 137 gti->tz_dev = devm_thermal_zone_of_sensor_register(&pdev->dev, 0, gti, 138 &gadc_thermal_ops); 139 if (IS_ERR(gti->tz_dev)) { 140 ret = PTR_ERR(gti->tz_dev); 141 dev_err(&pdev->dev, "Thermal zone sensor register failed: %d\n", 142 ret); 143 return ret; 144 } 145 146 return 0; 147 } 148 149 static const struct of_device_id of_adc_thermal_match[] = { 150 { .compatible = "generic-adc-thermal", }, 151 {}, 152 }; 153 MODULE_DEVICE_TABLE(of, of_adc_thermal_match); 154 155 static struct platform_driver gadc_thermal_driver = { 156 .driver = { 157 .name = "generic-adc-thermal", 158 .of_match_table = of_adc_thermal_match, 159 }, 160 .probe = gadc_thermal_probe, 161 }; 162 163 module_platform_driver(gadc_thermal_driver); 164 165 MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>"); 166 MODULE_DESCRIPTION("Generic ADC thermal driver using IIO framework with DT"); 167 MODULE_LICENSE("GPL v2"); 168