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 = tz->devdata; 58 int val; 59 int ret; 60 61 ret = iio_read_channel_processed(gti->channel, &val); 62 if (ret < 0) { 63 dev_err(gti->dev, "IIO channel read failed %d\n", ret); 64 return ret; 65 } 66 *temp = gadc_thermal_adc_to_temp(gti, val); 67 68 return 0; 69 } 70 71 static const struct thermal_zone_device_ops gadc_thermal_ops = { 72 .get_temp = gadc_thermal_get_temp, 73 }; 74 75 static int gadc_thermal_read_linear_lookup_table(struct device *dev, 76 struct gadc_thermal_info *gti) 77 { 78 struct device_node *np = dev->of_node; 79 enum iio_chan_type chan_type; 80 int ntable; 81 int ret; 82 83 ntable = of_property_count_elems_of_size(np, "temperature-lookup-table", 84 sizeof(u32)); 85 if (ntable <= 0) { 86 ret = iio_get_channel_type(gti->channel, &chan_type); 87 if (ret || chan_type != IIO_TEMP) 88 dev_notice(dev, 89 "no lookup table, assuming DAC channel returns milliCelcius\n"); 90 return 0; 91 } 92 93 if (ntable % 2) { 94 dev_err(dev, "Pair of temperature vs ADC read value missing\n"); 95 return -EINVAL; 96 } 97 98 gti->lookup_table = devm_kcalloc(dev, 99 ntable, sizeof(*gti->lookup_table), 100 GFP_KERNEL); 101 if (!gti->lookup_table) 102 return -ENOMEM; 103 104 ret = of_property_read_u32_array(np, "temperature-lookup-table", 105 (u32 *)gti->lookup_table, ntable); 106 if (ret < 0) { 107 dev_err(dev, "Failed to read temperature lookup table: %d\n", 108 ret); 109 return ret; 110 } 111 112 gti->nlookup_table = ntable / 2; 113 114 return 0; 115 } 116 117 static int gadc_thermal_probe(struct platform_device *pdev) 118 { 119 struct gadc_thermal_info *gti; 120 int ret; 121 122 if (!pdev->dev.of_node) { 123 dev_err(&pdev->dev, "Only DT based supported\n"); 124 return -ENODEV; 125 } 126 127 gti = devm_kzalloc(&pdev->dev, sizeof(*gti), GFP_KERNEL); 128 if (!gti) 129 return -ENOMEM; 130 131 gti->channel = devm_iio_channel_get(&pdev->dev, "sensor-channel"); 132 if (IS_ERR(gti->channel)) { 133 ret = PTR_ERR(gti->channel); 134 if (ret != -EPROBE_DEFER) 135 dev_err(&pdev->dev, "IIO channel not found: %d\n", ret); 136 return ret; 137 } 138 139 ret = gadc_thermal_read_linear_lookup_table(&pdev->dev, gti); 140 if (ret < 0) 141 return ret; 142 143 gti->dev = &pdev->dev; 144 platform_set_drvdata(pdev, gti); 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 return 0; 158 } 159 160 static const struct of_device_id of_adc_thermal_match[] = { 161 { .compatible = "generic-adc-thermal", }, 162 {}, 163 }; 164 MODULE_DEVICE_TABLE(of, of_adc_thermal_match); 165 166 static struct platform_driver gadc_thermal_driver = { 167 .driver = { 168 .name = "generic-adc-thermal", 169 .of_match_table = of_adc_thermal_match, 170 }, 171 .probe = gadc_thermal_probe, 172 }; 173 174 module_platform_driver(gadc_thermal_driver); 175 176 MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>"); 177 MODULE_DESCRIPTION("Generic ADC thermal driver using IIO framework with DT"); 178 MODULE_LICENSE("GPL v2"); 179