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 gadc_thermal_info *gti; 121 int ret; 122 123 if (!pdev->dev.of_node) { 124 dev_err(&pdev->dev, "Only DT based supported\n"); 125 return -ENODEV; 126 } 127 128 gti = devm_kzalloc(&pdev->dev, sizeof(*gti), GFP_KERNEL); 129 if (!gti) 130 return -ENOMEM; 131 132 gti->channel = devm_iio_channel_get(&pdev->dev, "sensor-channel"); 133 if (IS_ERR(gti->channel)) { 134 ret = PTR_ERR(gti->channel); 135 if (ret != -EPROBE_DEFER) 136 dev_err(&pdev->dev, "IIO channel not found: %d\n", ret); 137 return ret; 138 } 139 140 ret = gadc_thermal_read_linear_lookup_table(&pdev->dev, gti); 141 if (ret < 0) 142 return ret; 143 144 gti->dev = &pdev->dev; 145 146 gti->tz_dev = devm_thermal_of_zone_register(&pdev->dev, 0, gti, 147 &gadc_thermal_ops); 148 if (IS_ERR(gti->tz_dev)) { 149 ret = PTR_ERR(gti->tz_dev); 150 if (ret != -EPROBE_DEFER) 151 dev_err(&pdev->dev, 152 "Thermal zone sensor register failed: %d\n", 153 ret); 154 return ret; 155 } 156 157 devm_thermal_add_hwmon_sysfs(&pdev->dev, gti->tz_dev); 158 159 return 0; 160 } 161 162 static const struct of_device_id of_adc_thermal_match[] = { 163 { .compatible = "generic-adc-thermal", }, 164 {}, 165 }; 166 MODULE_DEVICE_TABLE(of, of_adc_thermal_match); 167 168 static struct platform_driver gadc_thermal_driver = { 169 .driver = { 170 .name = "generic-adc-thermal", 171 .of_match_table = of_adc_thermal_match, 172 }, 173 .probe = gadc_thermal_probe, 174 }; 175 176 module_platform_driver(gadc_thermal_driver); 177 178 MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>"); 179 MODULE_DESCRIPTION("Generic ADC thermal driver using IIO framework with DT"); 180 MODULE_LICENSE("GPL v2"); 181