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-rw-r--r--drivers/hwmon/raspberrypi-hwmon.c292
1 files changed, 292 insertions, 0 deletions
diff --git a/drivers/hwmon/raspberrypi-hwmon.c b/drivers/hwmon/raspberrypi-hwmon.c
new file mode 100644
index 000000000..7b1d2829f
--- /dev/null
+++ b/drivers/hwmon/raspberrypi-hwmon.c
@@ -0,0 +1,292 @@
+// 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@i2se.com>
+ * Copyright (C) 2026 Shubham Chakraborty <chakrabortyshubham66@gmail.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 valid_inputs;
+ u32 last_throttled;
+ struct delayed_work get_values_poll_work;
+};
+
+static const char * const rpi_hwmon_labels[] = {
+ "core",
+ "sdram_c",
+ "sdram_i",
+ "sdram_p",
+};
+
+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");
+
+ hwmon_notify_event(data->hwmon_dev, hwmon_in, hwmon_in_lcrit_alarm, 0);
+}
+
+static int rpi_firmware_get_voltage(struct rpi_hwmon_data *data, u32 id,
+ long *val)
+{
+ struct rpi_firmware_get_voltage_request packet =
+ RPI_FIRMWARE_GET_VOLTAGE_REQUEST(id);
+ int ret;
+
+ ret = rpi_firmware_property(data->fw, RPI_FIRMWARE_GET_VOLTAGE,
+ &packet, sizeof(packet));
+ if (ret)
+ return ret;
+
+ *val = le32_to_cpu(packet.value) / 1000;
+ return 0;
+}
+
+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 void rpi_hwmon_cancel_poll_work(void *res)
+{
+ struct rpi_hwmon_data *data = res;
+
+ disable_delayed_work_sync(&data->get_values_poll_work);
+}
+
+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) {
+ switch (attr) {
+ case hwmon_in_input:
+ switch (channel) {
+ case 0:
+ return rpi_firmware_get_voltage(data,
+ RPI_FIRMWARE_VOLT_ID_CORE,
+ val);
+ case 1:
+ return rpi_firmware_get_voltage(data,
+ RPI_FIRMWARE_VOLT_ID_SDRAM_C,
+ val);
+ case 2:
+ return rpi_firmware_get_voltage(data,
+ RPI_FIRMWARE_VOLT_ID_SDRAM_I,
+ val);
+ case 3:
+ return rpi_firmware_get_voltage(data,
+ RPI_FIRMWARE_VOLT_ID_SDRAM_P,
+ val);
+ default:
+ return -EOPNOTSUPP;
+ }
+ case hwmon_in_lcrit_alarm:
+ if (channel == 0) {
+ *val = !!(data->last_throttled & UNDERVOLTAGE_STICKY_BIT);
+ return 0;
+ }
+ return -EOPNOTSUPP;
+ default:
+ return -EOPNOTSUPP;
+ }
+ }
+
+ return -EOPNOTSUPP;
+}
+
+static int rpi_read_string(struct device *dev, enum hwmon_sensor_types type,
+ u32 attr, int channel, const char **str)
+{
+ if (type == hwmon_in && attr == hwmon_in_label) {
+ if (channel >= ARRAY_SIZE(rpi_hwmon_labels))
+ return -EOPNOTSUPP;
+
+ *str = rpi_hwmon_labels[channel];
+ return 0;
+ }
+
+ return -EOPNOTSUPP;
+}
+
+static umode_t rpi_is_visible(const void *_data, enum hwmon_sensor_types type,
+ u32 attr, int channel)
+{
+ const struct rpi_hwmon_data *data = _data;
+
+ if (type == hwmon_in) {
+ switch (attr) {
+ case hwmon_in_input:
+ case hwmon_in_label:
+ if (!(data->valid_inputs & BIT(channel)))
+ return 0;
+ return 0444;
+ case hwmon_in_lcrit_alarm:
+ if (channel == 0)
+ return 0444;
+ return 0;
+ default:
+ return 0;
+ }
+ }
+
+ return 0;
+}
+
+static const struct hwmon_channel_info * const rpi_info[] = {
+ HWMON_CHANNEL_INFO(in,
+ HWMON_I_INPUT | HWMON_I_LABEL | HWMON_I_LCRIT_ALARM,
+ HWMON_I_INPUT | HWMON_I_LABEL,
+ HWMON_I_INPUT | HWMON_I_LABEL,
+ HWMON_I_INPUT | HWMON_I_LABEL),
+ NULL
+};
+
+static const struct hwmon_ops rpi_hwmon_ops = {
+ .is_visible = rpi_is_visible,
+ .read = rpi_read,
+ .read_string = rpi_read_string,
+};
+
+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;
+ long voltage;
+ 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);
+
+ ret = rpi_firmware_get_voltage(data, RPI_FIRMWARE_VOLT_ID_CORE,
+ &voltage);
+ if (!ret)
+ data->valid_inputs |= BIT(0);
+
+ ret = rpi_firmware_get_voltage(data, RPI_FIRMWARE_VOLT_ID_SDRAM_C,
+ &voltage);
+ if (!ret)
+ data->valid_inputs |= BIT(1);
+
+ ret = rpi_firmware_get_voltage(data, RPI_FIRMWARE_VOLT_ID_SDRAM_I,
+ &voltage);
+ if (!ret)
+ data->valid_inputs |= BIT(2);
+
+ ret = rpi_firmware_get_voltage(data, RPI_FIRMWARE_VOLT_ID_SDRAM_P,
+ &voltage);
+ if (!ret)
+ data->valid_inputs |= BIT(3);
+
+ data->hwmon_dev = devm_hwmon_device_register_with_info(dev, "rpi_volt",
+ data,
+ &rpi_chip_info,
+ NULL);
+ if (IS_ERR(data->hwmon_dev))
+ return PTR_ERR(data->hwmon_dev);
+
+ INIT_DELAYED_WORK(&data->get_values_poll_work, get_values_poll);
+ ret = devm_add_action_or_reset(dev, rpi_hwmon_cancel_poll_work, data);
+ if (ret)
+ return ret;
+ platform_set_drvdata(pdev, data);
+
+ schedule_delayed_work(&data->get_values_poll_work, 2 * HZ);
+
+ return 0;
+}
+
+static int rpi_hwmon_suspend(struct device *dev)
+{
+ struct rpi_hwmon_data *data = dev_get_drvdata(dev);
+
+ cancel_delayed_work_sync(&data->get_values_poll_work);
+
+ return 0;
+}
+
+static int rpi_hwmon_resume(struct device *dev)
+{
+ struct rpi_hwmon_data *data = dev_get_drvdata(dev);
+
+ get_values_poll(&data->get_values_poll_work.work);
+
+ return 0;
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(rpi_hwmon_pm_ops, rpi_hwmon_suspend,
+ rpi_hwmon_resume);
+
+static struct platform_driver rpi_hwmon_driver = {
+ .probe = rpi_hwmon_probe,
+ .driver = {
+ .name = "raspberrypi-hwmon",
+ .pm = pm_ptr(&rpi_hwmon_pm_ops),
+ },
+};
+module_platform_driver(rpi_hwmon_driver);
+
+MODULE_AUTHOR("Stefan Wahren <wahrenst@gmx.net>");
+MODULE_AUTHOR("Shubham Chakraborty <chakrabortyshubham66@gmail.com>");
+MODULE_DESCRIPTION("Raspberry Pi voltage sensor driver");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:raspberrypi-hwmon");
generated by cgit v1.3.1 (git 2.54.0) at 2026-10-29 13:26:05 +0000