On Fri, May 25, 2018 at 09:24:35PM +0200, Stefan Wahren wrote:
> Currently there is no easy way to detect undervoltage conditions on a
> remote Raspberry Pi. This hwmon driver retrieves the state of the
> undervoltage sensor via mailbox interface. The handling based on
> Noralf's modifications to the downstream firmware driver. In case of
> an undervoltage condition only an entry is written to the kernel log.
>
> CC: "Noralf Trønnes" <nor...@tronnes.org>
> Signed-off-by: Stefan Wahren <stefan.wah...@i2se.com>
Acked-by: Guenter Roeck <li...@roeck-us.net>
... assuming this will go through some arm tree.
> ---
> Documentation/hwmon/raspberrypi-hwmon | 22 +++++
> drivers/hwmon/Kconfig | 10 ++
> drivers/hwmon/Makefile | 1 +
> drivers/hwmon/raspberrypi-hwmon.c | 166
> ++++++++++++++++++++++++++++++++++
> 4 files changed, 199 insertions(+)
> create mode 100644 Documentation/hwmon/raspberrypi-hwmon
> create mode 100644 drivers/hwmon/raspberrypi-hwmon.c
>
> diff --git a/Documentation/hwmon/raspberrypi-hwmon
> b/Documentation/hwmon/raspberrypi-hwmon
> new file mode 100644
> index 0000000..3c92e2c
> --- /dev/null
> +++ b/Documentation/hwmon/raspberrypi-hwmon
> @@ -0,0 +1,22 @@
> +Kernel driver raspberrypi-hwmon
> +===============================
> +
> +Supported boards:
> + * Raspberry Pi A+ (via GPIO on SoC)
> + * Raspberry Pi B+ (via GPIO on SoC)
> + * Raspberry Pi 2 B (via GPIO on SoC)
> + * Raspberry Pi 3 B (via GPIO on port expander)
> + * Raspberry Pi 3 B+ (via PMIC)
> +
> +Author: Stefan Wahren <stefan.wah...@i2se.com>
> +
> +Description
> +-----------
> +
> +This driver periodically polls a mailbox property of the VC4 firmware to
> detect
> +undervoltage conditions.
> +
> +Sysfs entries
> +-------------
> +
> +in0_lcrit_alarm Undervoltage alarm
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index f10840a..fdaab82 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -1298,6 +1298,16 @@ config SENSORS_PWM_FAN
> This driver can also be built as a module. If so, the module
> will be called pwm-fan.
>
> +config SENSORS_RASPBERRYPI_HWMON
> + tristate "Raspberry Pi voltage monitor"
> + depends on RASPBERRYPI_FIRMWARE || COMPILE_TEST
> + help
> + If you say yes here you get support for voltage sensor on the
> + Raspberry Pi.
> +
> + This driver can also be built as a module. If so, the module
> + will be called raspberrypi-hwmon.
> +
> config SENSORS_SHT15
> tristate "Sensiron humidity and temperature sensors. SHT15 and compat."
> depends on GPIOLIB || COMPILE_TEST
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index e7d52a3..a929770 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -141,6 +141,7 @@ obj-$(CONFIG_SENSORS_PC87427) += pc87427.o
> obj-$(CONFIG_SENSORS_PCF8591) += pcf8591.o
> obj-$(CONFIG_SENSORS_POWR1220) += powr1220.o
> obj-$(CONFIG_SENSORS_PWM_FAN) += pwm-fan.o
> +obj-$(CONFIG_SENSORS_RASPBERRYPI_HWMON) += raspberrypi-hwmon.o
> obj-$(CONFIG_SENSORS_S3C) += s3c-hwmon.o
> obj-$(CONFIG_SENSORS_SCH56XX_COMMON)+= sch56xx-common.o
> obj-$(CONFIG_SENSORS_SCH5627) += sch5627.o
> diff --git a/drivers/hwmon/raspberrypi-hwmon.c
> b/drivers/hwmon/raspberrypi-hwmon.c
> new file mode 100644
> index 0000000..fb4e4a6
> --- /dev/null
> +++ b/drivers/hwmon/raspberrypi-hwmon.c
> @@ -0,0 +1,166 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Raspberry Pi voltage sensor driver
> + *
> + * Based on firmware/raspberrypi.c by Noralf Trønnes
> + *
> + * Copyright (C) 2018 Stefan Wahren <stefan.wah...@i2se.com>
> + */
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/hwmon.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +#include <linux/workqueue.h>
> +#include <soc/bcm2835/raspberrypi-firmware.h>
> +
> +#define UNDERVOLTAGE_STICKY_BIT BIT(16)
> +
> +struct rpi_hwmon_data {
> + struct device *hwmon_dev;
> + struct rpi_firmware *fw;
> + u32 last_throttled;
> + struct delayed_work get_values_poll_work;
> +};
> +
> +static void rpi_firmware_get_throttled(struct rpi_hwmon_data *data)
> +{
> + u32 new_uv, old_uv, value;
> + int ret;
> +
> + /* Request firmware to clear sticky bits */
> + value = 0xffff;
> +
> + ret = rpi_firmware_property(data->fw, RPI_FIRMWARE_GET_THROTTLED,
> + &value, sizeof(value));
> + if (ret) {
> + dev_err_once(data->hwmon_dev, "Failed to get throttled (%d)\n",
> + ret);
> + return;
> + }
> +
> + new_uv = value & UNDERVOLTAGE_STICKY_BIT;
> + old_uv = data->last_throttled & UNDERVOLTAGE_STICKY_BIT;
> + data->last_throttled = value;
> +
> + if (new_uv == old_uv)
> + return;
> +
> + if (new_uv)
> + dev_crit(data->hwmon_dev, "Undervoltage detected!\n");
> + else
> + dev_info(data->hwmon_dev, "Voltage normalised\n");
> +
> + sysfs_notify(&data->hwmon_dev->kobj, NULL, "in0_lcrit_alarm");
> +}
> +
> +static void get_values_poll(struct work_struct *work)
> +{
> + struct rpi_hwmon_data *data;
> +
> + data = container_of(work, struct rpi_hwmon_data,
> + get_values_poll_work.work);
> +
> + rpi_firmware_get_throttled(data);
> +
> + /*
> + * We can't run faster than the sticky shift (100ms) since we get
> + * flipping in the sticky bits that are cleared.
> + */
> + schedule_delayed_work(&data->get_values_poll_work, 2 * HZ);
> +}
> +
> +static int rpi_read(struct device *dev, enum hwmon_sensor_types type,
> + u32 attr, int channel, long *val)
> +{
> + struct rpi_hwmon_data *data = dev_get_drvdata(dev);
> +
> + *val = !!(data->last_throttled & UNDERVOLTAGE_STICKY_BIT);
> + return 0;
> +}
> +
> +static umode_t rpi_is_visible(const void *_data, enum hwmon_sensor_types
> type,
> + u32 attr, int channel)
> +{
> + return 0444;
> +}
> +
> +static const u32 rpi_in_config[] = {
> + HWMON_I_LCRIT_ALARM,
> + 0
> +};
> +
> +static const struct hwmon_channel_info rpi_in = {
> + .type = hwmon_in,
> + .config = rpi_in_config,
> +};
> +
> +static const struct hwmon_channel_info *rpi_info[] = {
> + &rpi_in,
> + NULL
> +};
> +
> +static const struct hwmon_ops rpi_hwmon_ops = {
> + .is_visible = rpi_is_visible,
> + .read = rpi_read,
> +};
> +
> +static const struct hwmon_chip_info rpi_chip_info = {
> + .ops = &rpi_hwmon_ops,
> + .info = rpi_info,
> +};
> +
> +static int rpi_hwmon_probe(struct platform_device *pdev)
> +{
> + struct device *dev = &pdev->dev;
> + struct rpi_hwmon_data *data;
> + int ret;
> +
> + data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
> + if (!data)
> + return -ENOMEM;
> +
> + /* Parent driver assure that firmware is correct */
> + data->fw = dev_get_drvdata(dev->parent);
> +
> + /* Init throttled */
> + ret = rpi_firmware_property(data->fw, RPI_FIRMWARE_GET_THROTTLED,
> + &data->last_throttled,
> + sizeof(data->last_throttled));
> +
> + data->hwmon_dev = devm_hwmon_device_register_with_info(dev, "rpi_volt",
> + data,
> + &rpi_chip_info,
> + NULL);
> +
> + INIT_DELAYED_WORK(&data->get_values_poll_work, get_values_poll);
> + platform_set_drvdata(pdev, data);
> +
> + if (!PTR_ERR_OR_ZERO(data->hwmon_dev))
> + schedule_delayed_work(&data->get_values_poll_work, 2 * HZ);
> +
> + return PTR_ERR_OR_ZERO(data->hwmon_dev);
> +}
> +
> +static int rpi_hwmon_remove(struct platform_device *pdev)
> +{
> + struct rpi_hwmon_data *data = platform_get_drvdata(pdev);
> +
> + cancel_delayed_work_sync(&data->get_values_poll_work);
> +
> + return 0;
> +}
> +
> +static struct platform_driver rpi_hwmon_driver = {
> + .probe = rpi_hwmon_probe,
> + .remove = rpi_hwmon_remove,
> + .driver = {
> + .name = "raspberrypi-hwmon",
> + },
> +};
> +module_platform_driver(rpi_hwmon_driver);
> +
> +MODULE_AUTHOR("Stefan Wahren <stefan.wah...@i2se.com>");
> +MODULE_DESCRIPTION("Raspberry Pi voltage sensor driver");
> +MODULE_LICENSE("GPL v2");
> --
> 2.7.4
>
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