// SPDX-License-Identifier: GPL-2.0-only
/*
 * 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>
 */

#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/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 label_show(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 temp1_input_show(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 fan1_input_show(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_RO(temp1_label, label, NSA320_TEMP);
static DEVICE_ATTR_RO(temp1_input);
static SENSOR_DEVICE_ATTR_RO(fan1_label, label, NSA320_FAN);
static DEVICE_ATTR_RO(fan1_input);

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_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");