drivers/hwmon/raspberrypi-hwmon.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Raspberry Pi voltage sensor driver
   4  *
   5  * Based on firmware/raspberrypi.c by Noralf Trønnes
   6  *
   7  * Copyright (C) 2018 Stefan Wahren <stefan.wahren@i2se.com>
   8  */
   9 #include <linux/device.h>
  10 #include <linux/err.h>
  11 #include <linux/hwmon.h>
  12 #include <linux/module.h>
  13 #include <linux/platform_device.h>
  14 #include <linux/slab.h>
  15 #include <linux/workqueue.h>
  16 #include <soc/bcm2835/raspberrypi-firmware.h>
  17
  18 #define UNDERVOLTAGE_STICKY_BIT BIT(16)
  19
  20 struct rpi_hwmon_data {
  21         struct device *hwmon_dev;
  22         struct rpi_firmware *fw;
  23         u32 last_throttled;
  24         struct delayed_work get_values_poll_work;
  25 };
  26
  27 static void rpi_firmware_get_throttled(struct rpi_hwmon_data *data)
  28 {
  29         u32 new_uv, old_uv, value;
  30         int ret;
  31
  32         /* Request firmware to clear sticky bits */
  33         value = 0xffff;
  34
  35         ret = rpi_firmware_property(data->fw, RPI_FIRMWARE_GET_THROTTLED,
  36                                     &value, sizeof(value));
  37         if (ret) {
  38                 dev_err_once(data->hwmon_dev, "Failed to get throttled (%d)\n",
  39                              ret);
  40                 return;
  41         }
  42
  43         new_uv = value & UNDERVOLTAGE_STICKY_BIT;
  44         old_uv = data->last_throttled & UNDERVOLTAGE_STICKY_BIT;
  45         data->last_throttled = value;
  46
  47         if (new_uv == old_uv)
  48                 return;
  49
  50         if (new_uv)
  51                 dev_crit(data->hwmon_dev, "Undervoltage detected!\n");
  52         else
  53                 dev_info(data->hwmon_dev, "Voltage normalised\n");
  54
  55         sysfs_notify(&data->hwmon_dev->kobj, NULL, "in0_lcrit_alarm");
  56 }
  57
  58 static void get_values_poll(struct work_struct *work)
  59 {
  60         struct rpi_hwmon_data *data;
  61
  62         data = container_of(work, struct rpi_hwmon_data,
  63                             get_values_poll_work.work);
  64
  65         rpi_firmware_get_throttled(data);
  66
  67         /*
  68          * We can't run faster than the sticky shift (100ms) since we get
  69          * flipping in the sticky bits that are cleared.
  70          */
  71         schedule_delayed_work(&data->get_values_poll_work, 2 * HZ);
  72 }
  73
  74 static int rpi_read(struct device *dev, enum hwmon_sensor_types type,
  75                     u32 attr, int channel, long *val)
  76 {
  77         struct rpi_hwmon_data *data = dev_get_drvdata(dev);
  78
  79         *val = !!(data->last_throttled & UNDERVOLTAGE_STICKY_BIT);
  80         return 0;
  81 }
  82
  83 static umode_t rpi_is_visible(const void *_data, enum hwmon_sensor_types type,
  84                               u32 attr, int channel)
  85 {
  86         return 0444;
  87 }
  88
  89 static const u32 rpi_in_config[] = {
  90         HWMON_I_LCRIT_ALARM,
  91         0
  92 };
  93
  94 static const struct hwmon_channel_info rpi_in = {
  95         .type = hwmon_in,
  96         .config = rpi_in_config,
  97 };
  98
  99 static const struct hwmon_channel_info *rpi_info[] = {
 100         &rpi_in,
 101         NULL
 102 };
 103
 104 static const struct hwmon_ops rpi_hwmon_ops = {
 105         .is_visible = rpi_is_visible,
 106         .read = rpi_read,
 107 };
 108
 109 static const struct hwmon_chip_info rpi_chip_info = {
 110         .ops = &rpi_hwmon_ops,
 111         .info = rpi_info,
 112 };
 113
 114 static int rpi_hwmon_probe(struct platform_device *pdev)
 115 {
 116         struct device *dev = &pdev->dev;
 117         struct rpi_hwmon_data *data;
 118         int ret;
 119
 120         data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
 121         if (!data)
 122                 return -ENOMEM;
 123
 124         /* Parent driver assure that firmware is correct */
 125         data->fw = dev_get_drvdata(dev->parent);
 126
 127         /* Init throttled */
 128         ret = rpi_firmware_property(data->fw, RPI_FIRMWARE_GET_THROTTLED,
 129                                     &data->last_throttled,
 130                                     sizeof(data->last_throttled));
 131
 132         data->hwmon_dev = devm_hwmon_device_register_with_info(dev, "rpi_volt",
 133                                                                data,
 134                                                                &rpi_chip_info,
 135                                                                NULL);
 136
 137         INIT_DELAYED_WORK(&data->get_values_poll_work, get_values_poll);
 138         platform_set_drvdata(pdev, data);
 139
 140         if (!PTR_ERR_OR_ZERO(data->hwmon_dev))
 141                 schedule_delayed_work(&data->get_values_poll_work, 2 * HZ);
 142
 143         return PTR_ERR_OR_ZERO(data->hwmon_dev);
 144 }
 145
 146 static int rpi_hwmon_remove(struct platform_device *pdev)
 147 {
 148         struct rpi_hwmon_data *data = platform_get_drvdata(pdev);
 149
 150         cancel_delayed_work_sync(&data->get_values_poll_work);
 151
 152         return 0;
 153 }
 154
 155 static struct platform_driver rpi_hwmon_driver = {
 156         .probe = rpi_hwmon_probe,
 157         .remove = rpi_hwmon_remove,
 158         .driver = {
 159                 .name = "raspberrypi-hwmon",
 160         },
 161 };
 162 module_platform_driver(rpi_hwmon_driver);
 163
 164 MODULE_AUTHOR("Stefan Wahren <stefan.wahren@i2se.com>");
 165 MODULE_DESCRIPTION("Raspberry Pi voltage sensor driver");
 166 MODULE_LICENSE("GPL v2");