1/*
  2 * drivers/hwmon/nsa320-hwmon.c
  3 *
  4 * ZyXEL NSA320 Media Servers
  5 * hardware monitoring
  6 *
  7 * Copyright (C) 2016 Adam Baker <linux@baker-net.org.uk>
  8 * based on a board file driver
  9 * Copyright (C) 2012 Peter Schildmann <linux@schildmann.info>
 10 *
 11 * This program is free software; you can redistribute it and/or modify it
 12 * under the terms of the GNU General Public License v2 as published by the
 13 * Free Software Foundation.
 14 *
 15 * This program is distributed in the hope that it will be useful, but WITHOUT
 16 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 17 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 18 * more details.
 19 */
 20
 21#include <linux/bitops.h>
 22#include <linux/delay.h>
 23#include <linux/err.h>
 24#include <linux/gpio/consumer.h>
 25#include <linux/hwmon.h>
 26#include <linux/hwmon-sysfs.h>
 27#include <linux/jiffies.h>
 28#include <linux/module.h>
 29#include <linux/mutex.h>
 30#include <linux/of.h>
 31#include <linux/of_device.h>
 32#include <linux/of_platform.h>
 33#include <linux/platform_device.h>
 34
 35/* Tests for error return values rely upon this value being < 0x80 */
 36#define MAGIC_NUMBER 0x55
 37
 38/*
 39 * The Zyxel hwmon MCU is a Holtek HT46R065 that is factory programmed
 40 * to perform temperature and fan speed monitoring. It is read by taking
 41 * the active pin low. The 32 bit output word is then clocked onto the
 42 * data line. The MSB of the data word is a magic nuber to indicate it
 43 * has been read correctly, the next byte is the fan speed (in hundreds
 44 * of RPM) and the last two bytes are the temperature (in tenths of a
 45 * degree)
 46 */
 47
 48struct nsa320_hwmon {
 49	struct mutex		update_lock;	/* lock GPIO operations */
 50	unsigned long		last_updated;	/* jiffies */
 51	unsigned long		mcu_data;
 52	struct gpio_desc	*act;
 53	struct gpio_desc	*clk;
 54	struct gpio_desc	*data;
 55};
 56
 57enum nsa320_inputs {
 58	NSA320_TEMP = 0,
 59	NSA320_FAN = 1,
 60};
 61
 62static const char * const nsa320_input_names[] = {
 63	[NSA320_TEMP] = "System Temperature",
 64	[NSA320_FAN] = "Chassis Fan",
 65};
 66
 67/*
 68 * Although this protocol looks similar to SPI the long delay
 69 * between the active (aka chip select) signal and the shorter
 70 * delay between clock pulses are needed for reliable operation.
 71 * The delays provided are taken from the manufacturer kernel,
 72 * testing suggest they probably incorporate a reasonable safety
 73 * margin. (The single device tested became unreliable if the
 74 * delay was reduced to 1/10th of this value.)
 75 */
 76static s32 nsa320_hwmon_update(struct device *dev)
 77{
 78	u32 mcu_data;
 79	u32 mask;
 80	struct nsa320_hwmon *hwmon = dev_get_drvdata(dev);
 81
 82	mutex_lock(&hwmon->update_lock);
 83
 84	mcu_data = hwmon->mcu_data;
 85
 86	if (time_after(jiffies, hwmon->last_updated + HZ) || mcu_data == 0) {
 87		gpiod_set_value(hwmon->act, 1);
 88		msleep(100);
 89
 90		mcu_data = 0;
 91		for (mask = BIT(31); mask; mask >>= 1) {
 92			gpiod_set_value(hwmon->clk, 0);
 93			usleep_range(100, 200);
 94			gpiod_set_value(hwmon->clk, 1);
 95			usleep_range(100, 200);
 96			if (gpiod_get_value(hwmon->data))
 97				mcu_data |= mask;
 98		}
 99
100		gpiod_set_value(hwmon->act, 0);
101		dev_dbg(dev, "Read raw MCU data %08x\n", mcu_data);
102
103		if ((mcu_data >> 24) != MAGIC_NUMBER) {
104			dev_dbg(dev, "Read invalid MCU data %08x\n", mcu_data);
105			mcu_data = -EIO;
106		} else {
107			hwmon->mcu_data = mcu_data;
108			hwmon->last_updated = jiffies;
109		}
110	}
111
112	mutex_unlock(&hwmon->update_lock);
113
114	return mcu_data;
115}
116
117static ssize_t show_label(struct device *dev,
118			  struct device_attribute *attr, char *buf)
119{
120	int channel = to_sensor_dev_attr(attr)->index;
121
122	return sprintf(buf, "%s\n", nsa320_input_names[channel]);
123}
124
125static ssize_t show_temp(struct device *dev, struct device_attribute *attr,
126			 char *buf)
127{
128	s32 mcu_data = nsa320_hwmon_update(dev);
129
130	if (mcu_data < 0)
131		return mcu_data;
132
133	return sprintf(buf, "%d\n", (mcu_data & 0xffff) * 100);
134}
135
136static ssize_t show_fan(struct device *dev, struct device_attribute *attr,
137			char *buf)
138{
139	s32 mcu_data = nsa320_hwmon_update(dev);
140
141	if (mcu_data < 0)
142		return mcu_data;
143
144	return sprintf(buf, "%d\n", ((mcu_data & 0xff0000) >> 16) * 100);
145}
146
147static SENSOR_DEVICE_ATTR(temp1_label, S_IRUGO, show_label, NULL, NSA320_TEMP);
148static DEVICE_ATTR(temp1_input, S_IRUGO, show_temp, NULL);
149static SENSOR_DEVICE_ATTR(fan1_label, S_IRUGO, show_label, NULL, NSA320_FAN);
150static DEVICE_ATTR(fan1_input, S_IRUGO, show_fan, NULL);
151
152static struct attribute *nsa320_attrs[] = {
153	&sensor_dev_attr_temp1_label.dev_attr.attr,
154	&dev_attr_temp1_input.attr,
155	&sensor_dev_attr_fan1_label.dev_attr.attr,
156	&dev_attr_fan1_input.attr,
157	NULL
158};
159
160ATTRIBUTE_GROUPS(nsa320);
161
162static const struct of_device_id of_nsa320_hwmon_match[] = {
163	{ .compatible = "zyxel,nsa320-mcu", },
164	{ },
165};
166
167static int nsa320_hwmon_probe(struct platform_device *pdev)
168{
169	struct nsa320_hwmon	*hwmon;
170	struct device		*classdev;
171
172	hwmon = devm_kzalloc(&pdev->dev, sizeof(*hwmon), GFP_KERNEL);
173	if (!hwmon)
174		return -ENOMEM;
175
176	/* Look up the GPIO pins to use */
177	hwmon->act = devm_gpiod_get(&pdev->dev, "act", GPIOD_OUT_LOW);
178	if (IS_ERR(hwmon->act))
179		return PTR_ERR(hwmon->act);
180
181	hwmon->clk = devm_gpiod_get(&pdev->dev, "clk", GPIOD_OUT_HIGH);
182	if (IS_ERR(hwmon->clk))
183		return PTR_ERR(hwmon->clk);
184
185	hwmon->data = devm_gpiod_get(&pdev->dev, "data", GPIOD_IN);
186	if (IS_ERR(hwmon->data))
187		return PTR_ERR(hwmon->data);
188
189	mutex_init(&hwmon->update_lock);
190
191	classdev = devm_hwmon_device_register_with_groups(&pdev->dev,
192					"nsa320", hwmon, nsa320_groups);
193
194	return PTR_ERR_OR_ZERO(classdev);
195
196}
197
198/* All allocations use devres so remove() is not needed. */
199
200static struct platform_driver nsa320_hwmon_driver = {
201	.probe = nsa320_hwmon_probe,
202	.driver = {
203		.name = "nsa320-hwmon",
204		.of_match_table = of_match_ptr(of_nsa320_hwmon_match),
205	},
206};
207
208module_platform_driver(nsa320_hwmon_driver);
209
210MODULE_DEVICE_TABLE(of, of_nsa320_hwmon_match);
211MODULE_AUTHOR("Peter Schildmann <linux@schildmann.info>");
212MODULE_AUTHOR("Adam Baker <linux@baker-net.org.uk>");
213MODULE_DESCRIPTION("NSA320 Hardware Monitoring");
214MODULE_LICENSE("GPL v2");
215MODULE_ALIAS("platform:nsa320-hwmon");