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 struct hwmon_channel_info *rpi_info[] = {
  90         HWMON_CHANNEL_INFO(in,
  91                            HWMON_I_LCRIT_ALARM),
  92         NULL
  93 };
  94
  95 static const struct hwmon_ops rpi_hwmon_ops = {
  96         .is_visible = rpi_is_visible,
  97         .read = rpi_read,
  98 };
  99
 100 static const struct hwmon_chip_info rpi_chip_info = {
 101         .ops = &rpi_hwmon_ops,
 102         .info = rpi_info,
 103 };
 104
 105 static int rpi_hwmon_probe(struct platform_device *pdev)
 106 {
 107         struct device *dev = &pdev->dev;
 108         struct rpi_hwmon_data *data;
 109
 110         data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
 111         if (!data)
 112                 return -ENOMEM;
 113
 114         /* Parent driver assure that firmware is correct */
 115         data->fw = dev_get_drvdata(dev->parent);
 116
 117         data->hwmon_dev = devm_hwmon_device_register_with_info(dev, "rpi_volt",
 118                                                                data,
 119                                                                &rpi_chip_info,
 120                                                                NULL);
 121
 122         INIT_DELAYED_WORK(&data->get_values_poll_work, get_values_poll);
 123         platform_set_drvdata(pdev, data);
 124
 125         if (!PTR_ERR_OR_ZERO(data->hwmon_dev))
 126                 schedule_delayed_work(&data->get_values_poll_work, 2 * HZ);
 127
 128         return PTR_ERR_OR_ZERO(data->hwmon_dev);
 129 }
 130
 131 static int rpi_hwmon_remove(struct platform_device *pdev)
 132 {
 133         struct rpi_hwmon_data *data = platform_get_drvdata(pdev);
 134
 135         cancel_delayed_work_sync(&data->get_values_poll_work);
 136
 137         return 0;
 138 }
 139
 140 static struct platform_driver rpi_hwmon_driver = {
 141         .probe = rpi_hwmon_probe,
 142         .remove = rpi_hwmon_remove,
 143         .driver = {
 144                 .name = "raspberrypi-hwmon",
 145         },
 146 };
 147 module_platform_driver(rpi_hwmon_driver);
 148
 149 MODULE_AUTHOR("Stefan Wahren <wahrenst@gmx.net>");
 150 MODULE_DESCRIPTION("Raspberry Pi voltage sensor driver");
 151 MODULE_LICENSE("GPL v2");
 152 MODULE_ALIAS("platform:raspberrypi-hwmon");