drivers/hwmon/sl28cpld-hwmon.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * sl28cpld hardware monitoring driver
   4  *
   5  * Copyright 2020 Kontron Europe GmbH
   6  */
   7
   8 #include <linux/bitfield.h>
   9 #include <linux/hwmon.h>
  10 #include <linux/kernel.h>
  11 #include <linux/mod_devicetable.h>
  12 #include <linux/module.h>
  13 #include <linux/platform_device.h>
  14 #include <linux/property.h>
  15 #include <linux/regmap.h>
  16
  17 #define FAN_INPUT               0x00
  18 #define   FAN_SCALE_X8          BIT(7)
  19 #define   FAN_VALUE_MASK        GENMASK(6, 0)
  20
  21 struct sl28cpld_hwmon {
  22         struct regmap *regmap;
  23         u32 offset;
  24 };
  25
  26 static int sl28cpld_hwmon_read(struct device *dev,
  27                                enum hwmon_sensor_types type, u32 attr,
  28                                int channel, long *input)
  29 {
  30         struct sl28cpld_hwmon *hwmon = dev_get_drvdata(dev);
  31         unsigned int value;
  32         int ret;
  33
  34         switch (attr) {
  35         case hwmon_fan_input:
  36                 ret = regmap_read(hwmon->regmap, hwmon->offset + FAN_INPUT,
  37                                   &value);
  38                 if (ret)
  39                         return ret;
  40                 /*
  41                  * The register has a 7 bit value and 1 bit which indicates the
  42                  * scale. If the MSB is set, then the lower 7 bit has to be
  43                  * multiplied by 8, to get the correct reading.
  44                  */
  45                 if (value & FAN_SCALE_X8)
  46                         value = FIELD_GET(FAN_VALUE_MASK, value) << 3;
  47
  48                 /*
  49                  * The counter period is 1000ms and the sysfs specification
  50                  * says we should assume 2 pulses per revolution.
  51                  */
  52                 value *= 60 / 2;
  53
  54                 break;
  55         default:
  56                 return -EOPNOTSUPP;
  57         }
  58
  59         *input = value;
  60         return 0;
  61 }
  62
  63 static const struct hwmon_channel_info * const sl28cpld_hwmon_info[] = {
  64         HWMON_CHANNEL_INFO(fan, HWMON_F_INPUT),
  65         NULL
  66 };
  67
  68 static const struct hwmon_ops sl28cpld_hwmon_ops = {
  69         .visible = 0444,
  70         .read = sl28cpld_hwmon_read,
  71 };
  72
  73 static const struct hwmon_chip_info sl28cpld_hwmon_chip_info = {
  74         .ops = &sl28cpld_hwmon_ops,
  75         .info = sl28cpld_hwmon_info,
  76 };
  77
  78 static int sl28cpld_hwmon_probe(struct platform_device *pdev)
  79 {
  80         struct sl28cpld_hwmon *hwmon;
  81         struct device *hwmon_dev;
  82         int ret;
  83
  84         if (!pdev->dev.parent)
  85                 return -ENODEV;
  86
  87         hwmon = devm_kzalloc(&pdev->dev, sizeof(*hwmon), GFP_KERNEL);
  88         if (!hwmon)
  89                 return -ENOMEM;
  90
  91         hwmon->regmap = dev_get_regmap(pdev->dev.parent, NULL);
  92         if (!hwmon->regmap)
  93                 return -ENODEV;
  94
  95         ret = device_property_read_u32(&pdev->dev, "reg", &hwmon->offset);
  96         if (ret)
  97                 return -EINVAL;
  98
  99         hwmon_dev = devm_hwmon_device_register_with_info(&pdev->dev,
 100                                 "sl28cpld_hwmon", hwmon,
 101                                 &sl28cpld_hwmon_chip_info, NULL);
 102         if (IS_ERR(hwmon_dev))
 103                 dev_err(&pdev->dev, "failed to register as hwmon device");
 104
 105         return PTR_ERR_OR_ZERO(hwmon_dev);
 106 }
 107
 108 static const struct of_device_id sl28cpld_hwmon_of_match[] = {
 109         { .compatible = "kontron,sl28cpld-fan" },
 110         {}
 111 };
 112 MODULE_DEVICE_TABLE(of, sl28cpld_hwmon_of_match);
 113
 114 static struct platform_driver sl28cpld_hwmon_driver = {
 115         .probe = sl28cpld_hwmon_probe,
 116         .driver = {
 117                 .name = "sl28cpld-fan",
 118                 .of_match_table = sl28cpld_hwmon_of_match,
 119         },
 120 };
 121 module_platform_driver(sl28cpld_hwmon_driver);
 122
 123 MODULE_DESCRIPTION("sl28cpld Hardware Monitoring Driver");
 124 MODULE_AUTHOR("Michael Walle <michael@walle.cc>");
 125 MODULE_LICENSE("GPL");