Currently there is no easy way to detect under-voltage conditions on a remote
Raspberry Pi. This hwmon driver retrieves the state of the under-voltage sensor
via mailbox interface. The handling based on Noralf's modifications to the
downstream firmware driver. In case of an under-voltage condition only an entry
is written to the kernel log.
CC: "Noralf Trønnes" <noralf@xxxxxxxxxxx>
Signed-off-by: Stefan Wahren <stefan.wahren@xxxxxxxx>
---
drivers/hwmon/Kconfig | 10 ++
drivers/hwmon/Makefile | 1 +
drivers/hwmon/raspberrypi-hwmon.c | 207 ++++++++++++++++++++++++++++++++++++++
3 files changed, 218 insertions(+)
create mode 100644 drivers/hwmon/raspberrypi-hwmon.c
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 768aed5..7f935cf 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 (ARCH_BCM2835 && RASPBERRYPI_FIRMWARE) || (COMPILE_TEST && !RASPBERRYPI_FIRMWARE)
+ 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..2003f6c
--- /dev/null
+++ b/drivers/hwmon/raspberrypi-hwmon.c
@@ -0,0 +1,207 @@
+// 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.wahren@xxxxxxxx>
+ */
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/module.h>
+#include <linux/of_device.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;
+
+ /* 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, "%s: Failed to get throttled (%d)\n",
+ __func__, 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, "Under-voltage detected! (0x%08x)\n",
+ value);
+ else
+ dev_info(data->hwmon_dev, "Voltage normalised (0x%08x)\n",
+ value);
+
+ 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);
+
+ if (type != hwmon_in)
+ return -EOPNOTSUPP;
+
+ if (attr != hwmon_in_lcrit_alarm)
+ return -EOPNOTSUPP;
+
+ if (channel)
+ return -EOPNOTSUPP;
+
+ *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)
+{
+ if (type != hwmon_in)
+ return 0;
+
+ if (attr != hwmon_in_lcrit_alarm)
+ return 0;
+
+ if (channel)
+ return 0;
+
+ 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 device_node *fw_node;
+ struct rpi_hwmon_data *data;
+ int ret;
+
+ data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+
+ fw_node = of_get_parent(dev->of_node);
+ if (!fw_node) {
+ dev_err(dev, "Missing firmware node\n");
+ return -ENOENT;
+ }
+
+ data->fw = rpi_firmware_get(fw_node);
+ of_node_put(fw_node);
+ if (!data->fw)
+ return -EPROBE_DEFER;
+
+ ret = rpi_firmware_property(data->fw, RPI_FIRMWARE_GET_THROTTLED,
+ &data->last_throttled,
+ sizeof(data->last_throttled));
+ if (ret) {
+ dev_info(dev, "Firmware doesn't support GET_THROTTLED\n");
+ return -EOPNOTSUPP;
+ }
+
+ 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 const struct of_device_id rpi_hwmon_of_match[] = {
+ { .compatible = "raspberrypi,bcm2835-hwmon", },
+ { /* sentinel */},
+};
+MODULE_DEVICE_TABLE(of, rpi_hwmon_of_match);
+
+static struct platform_driver rpi_hwmon_driver = {
+ .probe = rpi_hwmon_probe,
+ .remove = rpi_hwmon_remove,
+ .driver = {
+ .name = "raspberrypi-hwmon",
+ .of_match_table = rpi_hwmon_of_match,
+ },
+};
+module_platform_driver(rpi_hwmon_driver);
+
+MODULE_AUTHOR("Stefan Wahren <stefan.wahren@xxxxxxxx>");
+MODULE_DESCRIPTION("Raspberry Pi voltage sensor driver");
+MODULE_LICENSE("GPL v2");
--
2.7.4
--
To unsubscribe from this list: send the line "unsubscribe devicetree" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
