LXR linux/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
  21struct 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
  28static 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        sysfs_notify(&data->hwmon_dev->kobj, NULL, "in0_lcrit_alarm");
  57}
  58
  59static 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
  75static 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
  84static umode_t rpi_is_visible(const void *_data, enum hwmon_sensor_types type,
  85                              u32 attr, int channel)
  86{
  87        return 0444;
  88}
  89
  90static const struct hwmon_channel_info *rpi_info[] = {
  91        HWMON_CHANNEL_INFO(in,
  92                           HWMON_I_LCRIT_ALARM),
  93        NULL
  94};
  95
  96static const struct hwmon_ops rpi_hwmon_ops = {
  97        .is_visible = rpi_is_visible,
  98        .read = rpi_read,
  99};
 100
 101static const struct hwmon_chip_info rpi_chip_info = {
 102        .ops = &rpi_hwmon_ops,
 103        .info = rpi_info,
 104};
 105
 106static int rpi_hwmon_probe(struct platform_device *pdev)
 107{
 108        struct device *dev = &pdev->dev;
 109        struct rpi_hwmon_data *data;
 110        int ret;
 111
 112        data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
 113        if (!data)
 114                return -ENOMEM;
 115
 116        /* Parent driver assure that firmware is correct */
 117        data->fw = dev_get_drvdata(dev->parent);
 118
 119        data->hwmon_dev = devm_hwmon_device_register_with_info(dev, "rpi_volt",
 120                                                               data,
 121                                                               &rpi_chip_info,
 122                                                               NULL);
 123
 124        ret = devm_delayed_work_autocancel(dev, &data->get_values_poll_work,
 125                                           get_values_poll);
 126        if (ret)
 127                return ret;
 128        platform_set_drvdata(pdev, data);
 129
 130        if (!PTR_ERR_OR_ZERO(data->hwmon_dev))
 131                schedule_delayed_work(&data->get_values_poll_work, 2 * HZ);
 132
 133        return PTR_ERR_OR_ZERO(data->hwmon_dev);
 134}
 135
 136static struct platform_driver rpi_hwmon_driver = {
 137        .probe = rpi_hwmon_probe,
 138        .driver = {
 139                .name = "raspberrypi-hwmon",
 140        },
 141};
 142module_platform_driver(rpi_hwmon_driver);
 143
 144MODULE_AUTHOR("Stefan Wahren <wahrenst@gmx.net>");
 145MODULE_DESCRIPTION("Raspberry Pi voltage sensor driver");
 146MODULE_LICENSE("GPL v2");
 147MODULE_ALIAS("platform:raspberrypi-hwmon");
 148