hwmon: Create an NSA320 hardware monitoring driver

Create a driver to support the hardware monitoring chip present in
the Zyxel NSA320 and some of the other Zyxel NAS devices.

The driver reads fan speed and temperature from a suitably
pre-programmed MCU on the device.

Signed-off-by: Adam Baker <linux@baker-net.org.uk>
[groeck: Dropped .owner field initialization]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

1 files changed, 215 insertions, 0 deletions

diff --git a/drivers/hwmon/nsa320-hwmon.c b/drivers/hwmon/nsa320-hwmon.c
new file mode 100644
index 000000000000..0517a265741f
--- /dev/null
+++ b/drivers/hwmon/nsa320-hwmon.c
@@ -0,0 +1,215 @@
+/*
+ * drivers/hwmon/nsa320-hwmon.c
+ *
+ * ZyXEL NSA320 Media Servers
+ * hardware monitoring
+ *
+ * Copyright (C) 2016 Adam Baker <linux@baker-net.org.uk>
+ * based on a board file driver
+ * Copyright (C) 2012 Peter Schildmann <linux@schildmann.info>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License v2 as published by the
+ * Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ */
+
+#include <linux/bitops.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/jiffies.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+
+/* Tests for error return values rely upon this value being < 0x80 */
+#define MAGIC_NUMBER 0x55
+
+/*
+ * The Zyxel hwmon MCU is a Holtek HT46R065 that is factory programmed
+ * to perform temperature and fan speed monitoring. It is read by taking
+ * the active pin low. The 32 bit output word is then clocked onto the
+ * data line. The MSB of the data word is a magic nuber to indicate it
+ * has been read correctly, the next byte is the fan speed (in hundreds
+ * of RPM) and the last two bytes are the temperature (in tenths of a
+ * degree)
+ */
+
+struct nsa320_hwmon {
+	struct mutex		update_lock;	/* lock GPIO operations */
+	unsigned long		last_updated;	/* jiffies */
+	unsigned long		mcu_data;
+	struct gpio_desc	*act;
+	struct gpio_desc	*clk;
+	struct gpio_desc	*data;
+};
+
+enum nsa320_inputs {
+	NSA320_TEMP = 0,
+	NSA320_FAN = 1,
+};
+
+static const char * const nsa320_input_names[] = {
+	[NSA320_TEMP] = "System Temperature",
+	[NSA320_FAN] = "Chassis Fan",
+};
+
+/*
+ * Although this protocol looks similar to SPI the long delay
+ * between the active (aka chip select) signal and the shorter
+ * delay between clock pulses are needed for reliable operation.
+ * The delays provided are taken from the manufacturer kernel,
+ * testing suggest they probably incorporate a reasonable safety
+ * margin. (The single device tested became unreliable if the
+ * delay was reduced to 1/10th of this value.)
+ */
+static s32 nsa320_hwmon_update(struct device *dev)
+{
+	u32 mcu_data;
+	u32 mask;
+	struct nsa320_hwmon *hwmon = dev_get_drvdata(dev);
+
+	mutex_lock(&hwmon->update_lock);
+
+	mcu_data = hwmon->mcu_data;
+
+	if (time_after(jiffies, hwmon->last_updated + HZ) || mcu_data == 0) {
+		gpiod_set_value(hwmon->act, 1);
+		msleep(100);
+
+		mcu_data = 0;
+		for (mask = BIT(31); mask; mask >>= 1) {
+			gpiod_set_value(hwmon->clk, 0);
+			usleep_range(100, 200);
+			gpiod_set_value(hwmon->clk, 1);
+			usleep_range(100, 200);
+			if (gpiod_get_value(hwmon->data))
+				mcu_data |= mask;
+		}
+
+		gpiod_set_value(hwmon->act, 0);
+		dev_dbg(dev, "Read raw MCU data %08x\n", mcu_data);
+
+		if ((mcu_data >> 24) != MAGIC_NUMBER) {
+			dev_dbg(dev, "Read invalid MCU data %08x\n", mcu_data);
+			mcu_data = -EIO;
+		} else {
+			hwmon->mcu_data = mcu_data;
+			hwmon->last_updated = jiffies;
+		}
+	}
+
+	mutex_unlock(&hwmon->update_lock);
+
+	return mcu_data;
+}
+
+static ssize_t show_label(struct device *dev,
+			  struct device_attribute *attr, char *buf)
+{
+	int channel = to_sensor_dev_attr(attr)->index;
+
+	return sprintf(buf, "%s\n", nsa320_input_names[channel]);
+}
+
+static ssize_t show_temp(struct device *dev, struct device_attribute *attr,
+			 char *buf)
+{
+	s32 mcu_data = nsa320_hwmon_update(dev);
+
+	if (mcu_data < 0)
+		return mcu_data;
+
+	return sprintf(buf, "%d\n", (mcu_data & 0xffff) * 100);
+}
+
+static ssize_t show_fan(struct device *dev, struct device_attribute *attr,
+			char *buf)
+{
+	s32 mcu_data = nsa320_hwmon_update(dev);
+
+	if (mcu_data < 0)
+		return mcu_data;
+
+	return sprintf(buf, "%d\n", ((mcu_data & 0xff0000) >> 16) * 100);
+}
+
+static SENSOR_DEVICE_ATTR(temp1_label, S_IRUGO, show_label, NULL, NSA320_TEMP);
+static DEVICE_ATTR(temp1_input, S_IRUGO, show_temp, NULL);
+static SENSOR_DEVICE_ATTR(fan1_label, S_IRUGO, show_label, NULL, NSA320_FAN);
+static DEVICE_ATTR(fan1_input, S_IRUGO, show_fan, NULL);
+
+static struct attribute *nsa320_attrs[] = {
+	&sensor_dev_attr_temp1_label.dev_attr.attr,
+	&dev_attr_temp1_input.attr,
+	&sensor_dev_attr_fan1_label.dev_attr.attr,
+	&dev_attr_fan1_input.attr,
+	NULL
+};
+
+ATTRIBUTE_GROUPS(nsa320);
+
+static const struct of_device_id of_nsa320_hwmon_match[] = {
+	{ .compatible = "zyxel,nsa320-mcu", },
+	{ },
+};
+
+static int nsa320_hwmon_probe(struct platform_device *pdev)
+{
+	struct nsa320_hwmon	*hwmon;
+	struct device		*classdev;
+
+	hwmon = devm_kzalloc(&pdev->dev, sizeof(*hwmon), GFP_KERNEL);
+	if (!hwmon)
+		return -ENOMEM;
+
+	/* Look up the GPIO pins to use */
+	hwmon->act = devm_gpiod_get(&pdev->dev, "act", GPIOD_OUT_LOW);
+	if (IS_ERR(hwmon->act))
+		return PTR_ERR(hwmon->act);
+
+	hwmon->clk = devm_gpiod_get(&pdev->dev, "clk", GPIOD_OUT_HIGH);
+	if (IS_ERR(hwmon->clk))
+		return PTR_ERR(hwmon->clk);
+
+	hwmon->data = devm_gpiod_get(&pdev->dev, "data", GPIOD_IN);
+	if (IS_ERR(hwmon->data))
+		return PTR_ERR(hwmon->data);
+
+	mutex_init(&hwmon->update_lock);
+
+	classdev = devm_hwmon_device_register_with_groups(&pdev->dev,
+					"nsa320", hwmon, nsa320_groups);
+
+	return PTR_ERR_OR_ZERO(classdev);
+
+}
+
+/* All allocations use devres so remove() is not needed. */
+
+static struct platform_driver nsa320_hwmon_driver = {
+	.probe = nsa320_hwmon_probe,
+	.driver = {
+		.name = "nsa320-hwmon",
+		.of_match_table = of_match_ptr(of_nsa320_hwmon_match),
+	},
+};
+
+module_platform_driver(nsa320_hwmon_driver);
+
+MODULE_DEVICE_TABLE(of, of_nsa320_hwmon_match);
+MODULE_AUTHOR("Peter Schildmann <linux@schildmann.info>");
+MODULE_AUTHOR("Adam Baker <linux@baker-net.org.uk>");
+MODULE_DESCRIPTION("NSA320 Hardware Monitoring");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:nsa320-hwmon");