hwmon: Create an NSA320 hardware monitoring driver

Kernel driver nsa320_hwmon

==========================

Supported chips:

  * Holtek HT46R065 microcontroller with onboard firmware that configures

	it to act as a hardware monitor.

    Prefix: 'nsa320'

    Addresses scanned: none

    Datasheet: Not available, driver was reverse engineered based upon the

	Zyxel kernel source

Author:

  Adam Baker <linux@baker-net.org.uk>

Description

-----------

This chip is known to be used in the Zyxel NSA320 and NSA325 NAS Units and

also in some variants of the NSA310 but the driver has only been tested

on the NSA320. In all of these devices it is connected to the same 3 GPIO

lines which are used to provide chip select, clock and data lines. The

interface behaves similarly to SPI but at much lower speeds than are normally

used for SPI.

Following each chip select pulse the chip will generate a single 32 bit word

that contains 0x55 as a marker to indicate that data is being read correctly,

followed by an 8 bit fan speed in 100s of RPM and a 16 bit temperature in

tenths of a degree.

sysfs-Interface

---------------

temp1_input - temperature input

fan1_input - fan speed

Notes

-----

The access timings used in the driver are the same as used in the Zyxel

provided kernel. Testing has shown that if the delay between chip select and

the first clock pulse is reduced from 100 ms to just under 10ms then the chip

will not produce any output. If the duration of either phase of the clock

is reduced from 100 us to less than 15 us then data pulses are likely to be

read twice corrupting the output. The above analysis is based upon a sample

of one unit but suggests that the Zyxel provided delay values include a

reasonable tolerance.

The driver incorporates a limit that it will not check for updated values

faster than once a second. This is because the hardware takes a relatively long

time to read the data from the device and when it does it reads both temp and

fan speed. As the most likely case for two accesses in quick succession is

to read both of these values avoiding a second read delay is desirable.

	  This driver can also be built as a module.  If so, the module

	  will be called nct7904.

config SENSORS_NSA320

	tristate "ZyXEL NSA320 and compatible fan speed and temperature sensors"

	depends on GPIOLIB && OF

	depends on MACH_KIRKWOOD || COMPILE_TEST

	help

	  If you say yes here you get support for hardware monitoring

	  for the ZyXEL NSA320 Media Server and other compatible devices

	  (probably the NSA325 and some NSA310 variants).

	  The sensor data is taken from a Holtek HT46R065 microcontroller

	  connected to GPIO lines.

	  This driver can also be built as a module. If so, the module

	  will be called nsa320-hwmon.

config SENSORS_PCF8591

	tristate "Philips PCF8591 ADC/DAC"

	depends on I2C

obj-$(CONFIG_SENSORS_NCT6775)	+= nct6775.o

obj-$(CONFIG_SENSORS_NCT7802)	+= nct7802.o

obj-$(CONFIG_SENSORS_NCT7904)	+= nct7904.o

obj-$(CONFIG_SENSORS_NSA320)	+= nsa320-hwmon.o

obj-$(CONFIG_SENSORS_NTC_THERMISTOR)	+= ntc_thermistor.o

obj-$(CONFIG_SENSORS_PC87360)	+= pc87360.o

obj-$(CONFIG_SENSORS_PC87427)	+= pc87427.o

/*

 * 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");