drivers/watchdog/exar_wdt.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0+
 /*
  *	exar_wdt.c - Driver for the watchdog present in some
  *		     Exar/MaxLinear UART chips like the XR28V38x.
  *
  *	(c) Copyright 2022 D. Müller <d.mueller@elsoft.ch>.
  *
  */

 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

 #include <linux/io.h>
 #include <linux/list.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/slab.h>
 #include <linux/watchdog.h>

 #define DRV_NAME	"exar_wdt"

 static const unsigned short sio_config_ports[] = { 0x2e, 0x4e };
 static const unsigned char sio_enter_keys[] = { 0x67, 0x77, 0x87, 0xA0 };
 #define EXAR_EXIT_KEY	0xAA

 #define EXAR_LDN	0x07
 #define EXAR_DID	0x20
 #define EXAR_VID	0x23
 #define EXAR_WDT	0x26
 #define EXAR_ACT	0x30
 #define EXAR_RTBASE	0x60

 #define EXAR_WDT_LDEV	0x08

 #define EXAR_VEN_ID	0x13A8
 #define EXAR_DEV_382	0x0382
 #define EXAR_DEV_384	0x0384

 /* WDT runtime registers */
 #define WDT_CTRL	0x00
 #define WDT_VAL		0x01

 #define WDT_UNITS_10MS	0x0	/* the 10 millisec unit of the HW is not used */
 #define WDT_UNITS_SEC	0x2
 #define WDT_UNITS_MIN	0x4

 /* default WDT control for WDTOUT signal activ / rearm by read */
 #define EXAR_WDT_DEF_CONF	0

 struct wdt_pdev_node {
 	struct list_head list;
 	struct platform_device *pdev;
 	const char name[16];
 };

 struct wdt_priv {
 	/* the lock for WDT io operations */
 	spinlock_t io_lock;
 	struct resource wdt_res;
 	struct watchdog_device wdt_dev;
 	unsigned short did;
 	unsigned short config_port;
 	unsigned char enter_key;
 	unsigned char unit;
 	unsigned char timeout;
 };

 #define WATCHDOG_TIMEOUT 60

 static int timeout = WATCHDOG_TIMEOUT;
 module_param(timeout, int, 0);
 MODULE_PARM_DESC(timeout,
 		 "Watchdog timeout in seconds. 1<=timeout<=15300, default="
 		 __MODULE_STRING(WATCHDOG_TIMEOUT) ".");

 static bool nowayout = WATCHDOG_NOWAYOUT;
 module_param(nowayout, bool, 0);
 MODULE_PARM_DESC(nowayout,
 		 "Watchdog cannot be stopped once started (default="
 		 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

 static int exar_sio_enter(const unsigned short config_port,
 			  const unsigned char key)
 {
 	if (!request_muxed_region(config_port, 2, DRV_NAME))
 		return -EBUSY;

 	/* write the ENTER-KEY twice */
 	outb(key, config_port);
 	outb(key, config_port);

 	return 0;
 }

 static void exar_sio_exit(const unsigned short config_port)
 {
 	outb(EXAR_EXIT_KEY, config_port);
 	release_region(config_port, 2);
 }

 static unsigned char exar_sio_read(const unsigned short config_port,
 				   const unsigned char reg)
 {
 	outb(reg, config_port);
 	return inb(config_port + 1);
 }

 static void exar_sio_write(const unsigned short config_port,
 			   const unsigned char reg, const unsigned char val)
 {
 	outb(reg, config_port);
 	outb(val, config_port + 1);
 }

 static unsigned short exar_sio_read16(const unsigned short config_port,
 				      const unsigned char reg)
 {
 	unsigned char msb, lsb;

 	msb = exar_sio_read(config_port, reg);
 	lsb = exar_sio_read(config_port, reg + 1);

 	return (msb << 8) | lsb;
 }

 static void exar_sio_select_wdt(const unsigned short config_port)
 {
 	exar_sio_write(config_port, EXAR_LDN, EXAR_WDT_LDEV);
 }

 static void exar_wdt_arm(const struct wdt_priv *priv)
 {
 	unsigned short rt_base = priv->wdt_res.start;

 	/* write timeout value twice to arm watchdog */
 	outb(priv->timeout, rt_base + WDT_VAL);
 	outb(priv->timeout, rt_base + WDT_VAL);
 }

 static void exar_wdt_disarm(const struct wdt_priv *priv)
 {
 	unsigned short rt_base = priv->wdt_res.start;

 	/*
 	 * use two accesses with different values to make sure
 	 * that a combination of a previous single access and
 	 * the ones below with the same value are not falsely
 	 * interpreted as "arm watchdog"
 	 */
 	outb(0xFF, rt_base + WDT_VAL);
 	outb(0, rt_base + WDT_VAL);
 }

 static int exar_wdt_start(struct watchdog_device *wdog)
 {
 	struct wdt_priv *priv = watchdog_get_drvdata(wdog);
 	unsigned short rt_base = priv->wdt_res.start;

 	spin_lock(&priv->io_lock);

 	exar_wdt_disarm(priv);
 	outb(priv->unit, rt_base + WDT_CTRL);
 	exar_wdt_arm(priv);

 	spin_unlock(&priv->io_lock);
 	return 0;
 }

 static int exar_wdt_stop(struct watchdog_device *wdog)
 {
 	struct wdt_priv *priv = watchdog_get_drvdata(wdog);

 	spin_lock(&priv->io_lock);

 	exar_wdt_disarm(priv);

 	spin_unlock(&priv->io_lock);
 	return 0;
 }

 static int exar_wdt_keepalive(struct watchdog_device *wdog)
 {
 	struct wdt_priv *priv = watchdog_get_drvdata(wdog);
 	unsigned short rt_base = priv->wdt_res.start;

 	spin_lock(&priv->io_lock);

 	/* reading the WDT_VAL reg will feed the watchdog */
 	inb(rt_base + WDT_VAL);

 	spin_unlock(&priv->io_lock);
 	return 0;
 }

 static int exar_wdt_set_timeout(struct watchdog_device *wdog, unsigned int t)
 {
 	struct wdt_priv *priv = watchdog_get_drvdata(wdog);
 	bool unit_min = false;

 	/*
 	 * if new timeout is bigger then 255 seconds, change the
 	 * unit to minutes and round the timeout up to the next whole minute
 	 */
 	if (t > 255) {
 		unit_min = true;
 		t = DIV_ROUND_UP(t, 60);
 	}

 	/* save for later use in exar_wdt_start() */
 	priv->unit = unit_min ? WDT_UNITS_MIN : WDT_UNITS_SEC;
 	priv->timeout = t;

 	wdog->timeout = unit_min ? t * 60 : t;

 	if (watchdog_hw_running(wdog))
 		exar_wdt_start(wdog);

 	return 0;
 }

 static const struct watchdog_info exar_wdt_info = {
 	.options	= WDIOF_KEEPALIVEPING |
 			  WDIOF_SETTIMEOUT |
 			  WDIOF_MAGICCLOSE,
 	.identity	= "Exar/MaxLinear XR28V38x Watchdog",
 };

 static const struct watchdog_ops exar_wdt_ops = {
 	.owner		= THIS_MODULE,
 	.start		= exar_wdt_start,
 	.stop		= exar_wdt_stop,
 	.ping		= exar_wdt_keepalive,
 	.set_timeout	= exar_wdt_set_timeout,
 };

 static int exar_wdt_config(struct watchdog_device *wdog,
 			   const unsigned char conf)
 {
 	struct wdt_priv *priv = watchdog_get_drvdata(wdog);
 	int ret;

 	ret = exar_sio_enter(priv->config_port, priv->enter_key);
 	if (ret)
 		return ret;

 	exar_sio_select_wdt(priv->config_port);
 	exar_sio_write(priv->config_port, EXAR_WDT, conf);

 	exar_sio_exit(priv->config_port);

 	return 0;
 }

 static int __init exar_wdt_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct wdt_priv *priv = dev->platform_data;
 	struct watchdog_device *wdt_dev = &priv->wdt_dev;
 	struct resource *res;
 	int ret;

 	res = platform_get_resource(pdev, IORESOURCE_IO, 0);
 	if (!res)
 		return -ENXIO;

 	spin_lock_init(&priv->io_lock);

 	wdt_dev->info = &exar_wdt_info;
 	wdt_dev->ops = &exar_wdt_ops;
 	wdt_dev->min_timeout = 1;
 	wdt_dev->max_timeout = 255 * 60;

 	watchdog_init_timeout(wdt_dev, timeout, NULL);
 	watchdog_set_nowayout(wdt_dev, nowayout);
 	watchdog_stop_on_reboot(wdt_dev);
 	watchdog_stop_on_unregister(wdt_dev);
 	watchdog_set_drvdata(wdt_dev, priv);

 	ret = exar_wdt_config(wdt_dev, EXAR_WDT_DEF_CONF);
 	if (ret)
 		return ret;

 	exar_wdt_set_timeout(wdt_dev, timeout);
 	/* Make sure that the watchdog is not running */
 	exar_wdt_stop(wdt_dev);

 	ret = devm_watchdog_register_device(dev, wdt_dev);
 	if (ret)
 		return ret;

 	dev_info(dev, "XR28V%X WDT initialized. timeout=%d sec (nowayout=%d)\n",
 		 priv->did, timeout, nowayout);

 	return 0;
 }

 static unsigned short __init exar_detect(const unsigned short config_port,
 					 const unsigned char key,
 					 unsigned short *rt_base)
 {
 	int ret;
 	unsigned short base = 0;
 	unsigned short vid, did;

 	ret = exar_sio_enter(config_port, key);
 	if (ret)
 		return 0;

 	vid = exar_sio_read16(config_port, EXAR_VID);
 	did = exar_sio_read16(config_port, EXAR_DID);

 	/* check for the vendor and device IDs we currently know about */
 	if (vid == EXAR_VEN_ID &&
 	    (did == EXAR_DEV_382 ||
 	     did == EXAR_DEV_384)) {
 		exar_sio_select_wdt(config_port);
 		/* is device active? */
 		if (exar_sio_read(config_port, EXAR_ACT) == 0x01)
 			base = exar_sio_read16(config_port, EXAR_RTBASE);
 	}

 	exar_sio_exit(config_port);

 	if (base) {
 		pr_debug("Found a XR28V%X WDT (conf: 0x%x / rt: 0x%04x)\n",
 			 did, config_port, base);
 		*rt_base = base;
 		return did;
 	}

 	return 0;
 }

 static struct platform_driver exar_wdt_driver = {
 	.driver = {
 		.name = DRV_NAME,
 	},
 };

 static LIST_HEAD(pdev_list);

 static int __init exar_wdt_register(struct wdt_priv *priv, const int idx)
 {
 	struct wdt_pdev_node *n;

 	n = kzalloc(sizeof(*n), GFP_KERNEL);
 	if (!n)
 		return -ENOMEM;

 	INIT_LIST_HEAD(&n->list);

 	scnprintf((char *)n->name, sizeof(n->name), DRV_NAME ".%d", idx);
 	priv->wdt_res.name = n->name;

 	n->pdev = platform_device_register_resndata(NULL, DRV_NAME, idx,
 						    &priv->wdt_res, 1,
 						    priv, sizeof(*priv));
 	if (IS_ERR(n->pdev)) {
 		kfree(n);
 		return PTR_ERR(n->pdev);
 	}

 	list_add_tail(&n->list, &pdev_list);

 	return 0;
 }

 static void exar_wdt_unregister(void)
 {
 	struct wdt_pdev_node *n, *t;

 	list_for_each_entry_safe(n, t, &pdev_list, list) {
 		platform_device_unregister(n->pdev);
 		list_del(&n->list);
 		kfree(n);
 	}
 }

 static int __init exar_wdt_init(void)
 {
 	int ret, i, j, idx = 0;

 	/* search for active Exar watchdogs on all possible locations */
 	for (i = 0; i < ARRAY_SIZE(sio_config_ports); i++) {
 		for (j = 0; j < ARRAY_SIZE(sio_enter_keys); j++) {
 			unsigned short did, rt_base = 0;

 			did = exar_detect(sio_config_ports[i],
 					  sio_enter_keys[j],
 					  &rt_base);

 			if (did) {
 				struct wdt_priv priv = {
 					.wdt_res = DEFINE_RES_IO(rt_base, 2),
 					.did = did,
 					.config_port = sio_config_ports[i],
 					.enter_key = sio_enter_keys[j],
 				};

 				ret = exar_wdt_register(&priv, idx);
 				if (!ret)
 					idx++;
 			}
 		}
 	}

 	if (!idx)
 		return -ENODEV;

 	ret = platform_driver_probe(&exar_wdt_driver, exar_wdt_probe);
 	if (ret)
 		exar_wdt_unregister();

 	return ret;
 }

 static void __exit exar_wdt_exit(void)
 {
 	exar_wdt_unregister();
 	platform_driver_unregister(&exar_wdt_driver);
 }

 module_init(exar_wdt_init);
 module_exit(exar_wdt_exit);

 MODULE_AUTHOR("David Müller <d.mueller@elsoft.ch>");
 MODULE_DESCRIPTION("Exar/MaxLinear Watchdog Driver");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* exar_wdt.c - Driver for the watchdog present in some
	* Exar/MaxLinear UART chips like the XR28V38x.
	*
	* (c) Copyright 2022 D. Müller <d.mueller@elsoft.ch>.
	*
	*/

	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

	#include <linux/io.h>
	#include <linux/list.h>
	#include <linux/module.h>
	#include <linux/platform_device.h>
	#include <linux/slab.h>
	#include <linux/watchdog.h>

	#define DRV_NAME "exar_wdt"

	static const unsigned short sio_config_ports[] = { 0x2e, 0x4e };
	static const unsigned char sio_enter_keys[] = { 0x67, 0x77, 0x87, 0xA0 };
	#define EXAR_EXIT_KEY 0xAA

	#define EXAR_LDN 0x07
	#define EXAR_DID 0x20
	#define EXAR_VID 0x23
	#define EXAR_WDT 0x26
	#define EXAR_ACT 0x30
	#define EXAR_RTBASE 0x60

	#define EXAR_WDT_LDEV 0x08

	#define EXAR_VEN_ID 0x13A8
	#define EXAR_DEV_382 0x0382
	#define EXAR_DEV_384 0x0384

	/* WDT runtime registers */
	#define WDT_CTRL 0x00
	#define WDT_VAL 0x01

	#define WDT_UNITS_10MS 0x0 /* the 10 millisec unit of the HW is not used */
	#define WDT_UNITS_SEC 0x2
	#define WDT_UNITS_MIN 0x4

	/* default WDT control for WDTOUT signal activ / rearm by read */
	#define EXAR_WDT_DEF_CONF 0

	struct wdt_pdev_node {
	struct list_head list;
	struct platform_device *pdev;
	const char name[16];
	};

	struct wdt_priv {
	/* the lock for WDT io operations */
	spinlock_t io_lock;
	struct resource wdt_res;
	struct watchdog_device wdt_dev;
	unsigned short did;
	unsigned short config_port;
	unsigned char enter_key;
	unsigned char unit;
	unsigned char timeout;
	};

	#define WATCHDOG_TIMEOUT 60

	static int timeout = WATCHDOG_TIMEOUT;
	module_param(timeout, int, 0);
	MODULE_PARM_DESC(timeout,
	"Watchdog timeout in seconds. 1<=timeout<=15300, default="
	__MODULE_STRING(WATCHDOG_TIMEOUT) ".");

	static bool nowayout = WATCHDOG_NOWAYOUT;
	module_param(nowayout, bool, 0);
	MODULE_PARM_DESC(nowayout,
	"Watchdog cannot be stopped once started (default="
	__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

	static int exar_sio_enter(const unsigned short config_port,
	const unsigned char key)
	{
	if (!request_muxed_region(config_port, 2, DRV_NAME))
	return -EBUSY;

	/* write the ENTER-KEY twice */
	outb(key, config_port);
	outb(key, config_port);

	return 0;
	}

	static void exar_sio_exit(const unsigned short config_port)
	{
	outb(EXAR_EXIT_KEY, config_port);
	release_region(config_port, 2);
	}

	static unsigned char exar_sio_read(const unsigned short config_port,
	const unsigned char reg)
	{
	outb(reg, config_port);
	return inb(config_port + 1);
	}

	static void exar_sio_write(const unsigned short config_port,
	const unsigned char reg, const unsigned char val)
	{
	outb(reg, config_port);
	outb(val, config_port + 1);
	}

	static unsigned short exar_sio_read16(const unsigned short config_port,
	const unsigned char reg)
	{
	unsigned char msb, lsb;

	msb = exar_sio_read(config_port, reg);
	lsb = exar_sio_read(config_port, reg + 1);

	return (msb << 8) \| lsb;
	}

	static void exar_sio_select_wdt(const unsigned short config_port)
	{
	exar_sio_write(config_port, EXAR_LDN, EXAR_WDT_LDEV);
	}

	static void exar_wdt_arm(const struct wdt_priv *priv)
	{
	unsigned short rt_base = priv->wdt_res.start;

	/* write timeout value twice to arm watchdog */
	outb(priv->timeout, rt_base + WDT_VAL);
	outb(priv->timeout, rt_base + WDT_VAL);
	}

	static void exar_wdt_disarm(const struct wdt_priv *priv)
	{
	unsigned short rt_base = priv->wdt_res.start;

	/*
	* use two accesses with different values to make sure
	* that a combination of a previous single access and
	* the ones below with the same value are not falsely
	* interpreted as "arm watchdog"
	*/
	outb(0xFF, rt_base + WDT_VAL);
	outb(0, rt_base + WDT_VAL);
	}

	static int exar_wdt_start(struct watchdog_device *wdog)
	{
	struct wdt_priv *priv = watchdog_get_drvdata(wdog);
	unsigned short rt_base = priv->wdt_res.start;

	spin_lock(&priv->io_lock);

	exar_wdt_disarm(priv);
	outb(priv->unit, rt_base + WDT_CTRL);
	exar_wdt_arm(priv);

	spin_unlock(&priv->io_lock);
	return 0;
	}

	static int exar_wdt_stop(struct watchdog_device *wdog)
	{
	struct wdt_priv *priv = watchdog_get_drvdata(wdog);

	spin_lock(&priv->io_lock);

	exar_wdt_disarm(priv);

	spin_unlock(&priv->io_lock);
	return 0;
	}

	static int exar_wdt_keepalive(struct watchdog_device *wdog)
	{
	struct wdt_priv *priv = watchdog_get_drvdata(wdog);
	unsigned short rt_base = priv->wdt_res.start;

	spin_lock(&priv->io_lock);

	/* reading the WDT_VAL reg will feed the watchdog */
	inb(rt_base + WDT_VAL);

	spin_unlock(&priv->io_lock);
	return 0;
	}

	static int exar_wdt_set_timeout(struct watchdog_device *wdog, unsigned int t)
	{
	struct wdt_priv *priv = watchdog_get_drvdata(wdog);
	bool unit_min = false;

	/*
	* if new timeout is bigger then 255 seconds, change the
	* unit to minutes and round the timeout up to the next whole minute
	*/
	if (t > 255) {
	unit_min = true;
	t = DIV_ROUND_UP(t, 60);
	}

	/* save for later use in exar_wdt_start() */
	priv->unit = unit_min ? WDT_UNITS_MIN : WDT_UNITS_SEC;
	priv->timeout = t;

	wdog->timeout = unit_min ? t * 60 : t;

	if (watchdog_hw_running(wdog))
	exar_wdt_start(wdog);

	return 0;
	}

	static const struct watchdog_info exar_wdt_info = {
	.options = WDIOF_KEEPALIVEPING \|
	WDIOF_SETTIMEOUT \|
	WDIOF_MAGICCLOSE,
	.identity = "Exar/MaxLinear XR28V38x Watchdog",
	};

	static const struct watchdog_ops exar_wdt_ops = {
	.owner = THIS_MODULE,
	.start = exar_wdt_start,
	.stop = exar_wdt_stop,
	.ping = exar_wdt_keepalive,
	.set_timeout = exar_wdt_set_timeout,
	};

	static int exar_wdt_config(struct watchdog_device *wdog,
	const unsigned char conf)
	{
	struct wdt_priv *priv = watchdog_get_drvdata(wdog);
	int ret;

	ret = exar_sio_enter(priv->config_port, priv->enter_key);
	if (ret)
	return ret;

	exar_sio_select_wdt(priv->config_port);
	exar_sio_write(priv->config_port, EXAR_WDT, conf);

	exar_sio_exit(priv->config_port);

	return 0;
	}

	static int __init exar_wdt_probe(struct platform_device *pdev)
	{
	struct device *dev = &pdev->dev;
	struct wdt_priv *priv = dev->platform_data;
	struct watchdog_device *wdt_dev = &priv->wdt_dev;
	struct resource *res;
	int ret;

	res = platform_get_resource(pdev, IORESOURCE_IO, 0);
	if (!res)
	return -ENXIO;

	spin_lock_init(&priv->io_lock);

	wdt_dev->info = &exar_wdt_info;
	wdt_dev->ops = &exar_wdt_ops;
	wdt_dev->min_timeout = 1;
	wdt_dev->max_timeout = 255 * 60;

	watchdog_init_timeout(wdt_dev, timeout, NULL);
	watchdog_set_nowayout(wdt_dev, nowayout);
	watchdog_stop_on_reboot(wdt_dev);
	watchdog_stop_on_unregister(wdt_dev);
	watchdog_set_drvdata(wdt_dev, priv);

	ret = exar_wdt_config(wdt_dev, EXAR_WDT_DEF_CONF);
	if (ret)
	return ret;

	exar_wdt_set_timeout(wdt_dev, timeout);
	/* Make sure that the watchdog is not running */
	exar_wdt_stop(wdt_dev);

	ret = devm_watchdog_register_device(dev, wdt_dev);
	if (ret)
	return ret;

	dev_info(dev, "XR28V%X WDT initialized. timeout=%d sec (nowayout=%d)\n",
	priv->did, timeout, nowayout);

	return 0;
	}

	static unsigned short __init exar_detect(const unsigned short config_port,
	const unsigned char key,
	unsigned short *rt_base)
	{
	int ret;
	unsigned short base = 0;
	unsigned short vid, did;

	ret = exar_sio_enter(config_port, key);
	if (ret)
	return 0;

	vid = exar_sio_read16(config_port, EXAR_VID);
	did = exar_sio_read16(config_port, EXAR_DID);

	/* check for the vendor and device IDs we currently know about */
	if (vid == EXAR_VEN_ID &&
	(did == EXAR_DEV_382 \|\|
	did == EXAR_DEV_384)) {
	exar_sio_select_wdt(config_port);
	/* is device active? */
	if (exar_sio_read(config_port, EXAR_ACT) == 0x01)
	base = exar_sio_read16(config_port, EXAR_RTBASE);
	}

	exar_sio_exit(config_port);

	if (base) {
	pr_debug("Found a XR28V%X WDT (conf: 0x%x / rt: 0x%04x)\n",
	did, config_port, base);
	*rt_base = base;
	return did;
	}

	return 0;
	}

	static struct platform_driver exar_wdt_driver = {
	.driver = {
	.name = DRV_NAME,
	},
	};

	static LIST_HEAD(pdev_list);

	static int __init exar_wdt_register(struct wdt_priv *priv, const int idx)
	{
	struct wdt_pdev_node *n;

	n = kzalloc(sizeof(*n), GFP_KERNEL);
	if (!n)
	return -ENOMEM;

	INIT_LIST_HEAD(&n->list);

	scnprintf((char *)n->name, sizeof(n->name), DRV_NAME ".%d", idx);
	priv->wdt_res.name = n->name;

	n->pdev = platform_device_register_resndata(NULL, DRV_NAME, idx,
	&priv->wdt_res, 1,
	priv, sizeof(*priv));
	if (IS_ERR(n->pdev)) {
	kfree(n);
	return PTR_ERR(n->pdev);
	}

	list_add_tail(&n->list, &pdev_list);

	return 0;
	}

	static void exar_wdt_unregister(void)
	{
	struct wdt_pdev_node n, t;

	list_for_each_entry_safe(n, t, &pdev_list, list) {
	platform_device_unregister(n->pdev);
	list_del(&n->list);
	kfree(n);
	}
	}

	static int __init exar_wdt_init(void)
	{
	int ret, i, j, idx = 0;

	/* search for active Exar watchdogs on all possible locations */
	for (i = 0; i < ARRAY_SIZE(sio_config_ports); i++) {
	for (j = 0; j < ARRAY_SIZE(sio_enter_keys); j++) {
	unsigned short did, rt_base = 0;

	did = exar_detect(sio_config_ports[i],
	sio_enter_keys[j],
	&rt_base);

	if (did) {
	struct wdt_priv priv = {
	.wdt_res = DEFINE_RES_IO(rt_base, 2),
	.did = did,
	.config_port = sio_config_ports[i],
	.enter_key = sio_enter_keys[j],
	};

	ret = exar_wdt_register(&priv, idx);
	if (!ret)
	idx++;
	}
	}
	}

	if (!idx)
	return -ENODEV;

	ret = platform_driver_probe(&exar_wdt_driver, exar_wdt_probe);
	if (ret)
	exar_wdt_unregister();

	return ret;
	}

	static void __exit exar_wdt_exit(void)
	{
	exar_wdt_unregister();
	platform_driver_unregister(&exar_wdt_driver);
	}

	module_init(exar_wdt_init);
	module_exit(exar_wdt_exit);

	MODULE_AUTHOR("David Müller <d.mueller@elsoft.ch>");
	MODULE_DESCRIPTION("Exar/MaxLinear Watchdog Driver");
	MODULE_LICENSE("GPL");