Re: [PATCH RFC 3/6] hwmon: Add support for RPi voltage sensor

[Guenter Roeck <linux@roeck-us.net>]

On Wed, May 16, 2018 at 02:51:49PM +0100, Robin Murphy wrote:
> Hi Stefan,
> 
> On 16/05/18 14:37, Stefan Wahren wrote:
> >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@tronnes.org>
> >Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
> >---
> >  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)
> 
> Since RASPBERRYPI_FIRMWARE already implies ARCH_BCM2835 (via BCM2835_MBOX),
> this is just a very roundabout way to say:
> 
> 	depends on RASPBERRYPI_FIRMWARE || COMPILE_TEST
> 
That would permit SENSORS_RASPBERRYPI_HWMON=y combined with
RASPBERRYPI_FIRMWARE=m, which AFAICS would result in a build error
because include/soc/bcm2835/raspberrypi-firmware.h uses IS_ENABLED()
and not IS_REACHABLE().

Guenter

> Robin.
> 
> >+	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@i2se.com>
> >+ */
> >+#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@i2se.com>");
> >+MODULE_DESCRIPTION("Raspberry Pi voltage sensor driver");
> >+MODULE_LICENSE("GPL v2");
> >
> --
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