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/devm-helpers.h>
  11 #include <linux/err.h>
  12 #include <linux/hwmon.h>
  13 #include <linux/module.h>
  14 #include <linux/platform_device.h>
  15 #include <linux/slab.h>
  16 #include <linux/workqueue.h>
  17 #include <soc/bcm2835/raspberrypi-firmware.h>
  18
  19 #define UNDERVOLTAGE_STICKY_BIT BIT(16)
  20
  21 struct rpi_hwmon_data {
  22         struct device *hwmon_dev;
  23         struct rpi_firmware *fw;
  24         u32 last_throttled;
  25         struct delayed_work get_values_poll_work;
  26 };
  27
  28 static void rpi_firmware_get_throttled(struct rpi_hwmon_data *data)
  29 {
  30         u32 new_uv, old_uv, value;
  31         int ret;
  32
  33         /* Request firmware to clear sticky bits */
  34         value = 0xffff;
  35
  36         ret = rpi_firmware_property(data->fw, RPI_FIRMWARE_GET_THROTTLED,
  37                                     &value, sizeof(value));
  38         if (ret) {
  39                 dev_err_once(data->hwmon_dev, "Failed to get throttled (%d)\n",
  40                              ret);
  41                 return;
  42         }
  43
  44         new_uv = value & UNDERVOLTAGE_STICKY_BIT;
  45         old_uv = data->last_throttled & UNDERVOLTAGE_STICKY_BIT;
  46         data->last_throttled = value;
  47
  48         if (new_uv == old_uv)
  49                 return;
  50
  51         if (new_uv)
  52                 dev_crit(data->hwmon_dev, "Undervoltage detected!\n");
  53         else
  54                 dev_info(data->hwmon_dev, "Voltage normalised\n");
  55
  56         hwmon_notify_event(data->hwmon_dev, hwmon_in, hwmon_in_lcrit_alarm, 0);
  57 }
  58
  59 static void get_values_poll(struct work_struct *work)
  60 {
  61         struct rpi_hwmon_data *data;
  62
  63         data = container_of(work, struct rpi_hwmon_data,
  64                             get_values_poll_work.work);
  65
  66         rpi_firmware_get_throttled(data);
  67
  68         /*
  69          * We can't run faster than the sticky shift (100ms) since we get
  70          * flipping in the sticky bits that are cleared.
  71          */
  72         schedule_delayed_work(&data->get_values_poll_work, 2 * HZ);
  73 }
  74
  75 static int rpi_read(struct device *dev, enum hwmon_sensor_types type,
  76                     u32 attr, int channel, long *val)
  77 {
  78         struct rpi_hwmon_data *data = dev_get_drvdata(dev);
  79
  80         *val = !!(data->last_throttled & UNDERVOLTAGE_STICKY_BIT);
  81         return 0;
  82 }
  83
  84 static const struct hwmon_channel_info * const rpi_info[] = {
  85         HWMON_CHANNEL_INFO(in,
  86                            HWMON_I_LCRIT_ALARM),
  87         NULL
  88 };
  89
  90 static const struct hwmon_ops rpi_hwmon_ops = {
  91         .visible = 0444,
  92         .read = rpi_read,
  93 };
  94
  95 static const struct hwmon_chip_info rpi_chip_info = {
  96         .ops = &rpi_hwmon_ops,
  97         .info = rpi_info,
  98 };
  99
 100 static int rpi_hwmon_probe(struct platform_device *pdev)
 101 {
 102         struct device *dev = &pdev->dev;
 103         struct rpi_hwmon_data *data;
 104         int ret;
 105
 106         data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
 107         if (!data)
 108                 return -ENOMEM;
 109
 110         /* Parent driver assure that firmware is correct */
 111         data->fw = dev_get_drvdata(dev->parent);
 112
 113         data->hwmon_dev = devm_hwmon_device_register_with_info(dev, "rpi_volt",
 114                                                                data,
 115                                                                &rpi_chip_info,
 116                                                                NULL);
 117         if (IS_ERR(data->hwmon_dev))
 118                 return PTR_ERR(data->hwmon_dev);
 119
 120         ret = devm_delayed_work_autocancel(dev, &data->get_values_poll_work,
 121                                            get_values_poll);
 122         if (ret)
 123                 return ret;
 124         platform_set_drvdata(pdev, data);
 125
 126         schedule_delayed_work(&data->get_values_poll_work, 2 * HZ);
 127
 128         return 0;
 129 }
 130
 131 static struct platform_driver rpi_hwmon_driver = {
 132         .probe = rpi_hwmon_probe,
 133         .driver = {
 134                 .name = "raspberrypi-hwmon",
 135         },
 136 };
 137 module_platform_driver(rpi_hwmon_driver);
 138
 139 MODULE_AUTHOR("Stefan Wahren <wahrenst@gmx.net>");
 140 MODULE_DESCRIPTION("Raspberry Pi voltage sensor driver");
 141 MODULE_LICENSE("GPL v2");
 142 MODULE_ALIAS("platform:raspberrypi-hwmon");