drivers/misc/mei/wd.c - maze/linux - Git at Google

 /*
  *
  * Intel Management Engine Interface (Intel MEI) Linux driver
  * Copyright (c) 2003-2012, Intel Corporation.
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms and conditions of the GNU General Public License,
  * version 2, as published by the Free Software Foundation.
  *
  * This program is distributed in the hope 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/kernel.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
 #include <linux/device.h>
 #include <linux/pci.h>
 #include <linux/sched.h>
 #include <linux/watchdog.h>

 #include <linux/mei.h>

 #include "mei_dev.h"
 #include "hbm.h"
 #include "client.h"

 static const u8 mei_start_wd_params[] = { 0x02, 0x12, 0x13, 0x10 };
 static const u8 mei_stop_wd_params[] = { 0x02, 0x02, 0x14, 0x10 };

 /*
  * AMT Watchdog Device
  */
 #define INTEL_AMT_WATCHDOG_ID "INTCAMT"

 /* UUIDs for AMT F/W clients */
 const uuid_le mei_wd_guid = UUID_LE(0x05B79A6F, 0x4628, 0x4D7F, 0x89,
 						0x9D, 0xA9, 0x15, 0x14, 0xCB,
 						0x32, 0xAB);

 static void mei_wd_set_start_timeout(struct mei_device *dev, u16 timeout)
 {
 	dev_dbg(&dev->pdev->dev, "wd: set timeout=%d.\n", timeout);
 	memcpy(dev->wd_data, mei_start_wd_params, MEI_WD_HDR_SIZE);
 	memcpy(dev->wd_data + MEI_WD_HDR_SIZE, &timeout, sizeof(u16));
 }

 /**
  * mei_wd_host_init - connect to the watchdog client
  *
  * @dev: the device structure
  *
  * returns -ENOTTY if wd client cannot be found
  *         -EIO if write has failed
  *         0 on success
  */
 int mei_wd_host_init(struct mei_device *dev)
 {
 	struct mei_cl *cl = &dev->wd_cl;
 	int id;
 	int ret;

 	mei_cl_init(cl, dev);

 	dev->wd_timeout = MEI_WD_DEFAULT_TIMEOUT;
 	dev->wd_state = MEI_WD_IDLE;


 	/* check for valid client id */
 	id = mei_me_cl_by_uuid(dev, &mei_wd_guid);
 	if (id < 0) {
 		dev_info(&dev->pdev->dev, "wd: failed to find the client\n");
 		return -ENOTTY;
 	}

 	cl->me_client_id = dev->me_clients[id].client_id;

 	ret = mei_cl_link(cl, MEI_WD_HOST_CLIENT_ID);

 	if (ret < 0) {
 		dev_info(&dev->pdev->dev, "wd: failed link client\n");
 		return ret;
 	}

 	cl->state = MEI_FILE_CONNECTING;

 	ret = mei_cl_connect(cl, NULL);

 	if (ret) {
 		dev_err(&dev->pdev->dev, "wd: failed to connect = %d\n", ret);
 		mei_cl_unlink(cl);
 		return ret;
 	}

 	ret = mei_watchdog_register(dev);
 	if (ret) {
 		mei_cl_disconnect(cl);
 		mei_cl_unlink(cl);
 	}
 	return ret;
 }

 /**
  * mei_wd_send - sends watch dog message to fw.
  *
  * @dev: the device structure
  *
  * returns 0 if success,
  *	-EIO when message send fails
  *	-EINVAL when invalid message is to be sent
  *	-ENODEV on flow control failure
  */
 int mei_wd_send(struct mei_device *dev)
 {
 	struct mei_cl *cl = &dev->wd_cl;
 	struct mei_msg_hdr hdr;
 	int ret;

 	hdr.host_addr = cl->host_client_id;
 	hdr.me_addr = cl->me_client_id;
 	hdr.msg_complete = 1;
 	hdr.reserved = 0;
 	hdr.internal = 0;

 	if (!memcmp(dev->wd_data, mei_start_wd_params, MEI_WD_HDR_SIZE))
 		hdr.length = MEI_WD_START_MSG_SIZE;
 	else if (!memcmp(dev->wd_data, mei_stop_wd_params, MEI_WD_HDR_SIZE))
 		hdr.length = MEI_WD_STOP_MSG_SIZE;
 	else {
 		dev_err(&dev->pdev->dev, "wd: invalid message is to be sent, aborting\n");
 		return -EINVAL;
 	}

 	ret = mei_write_message(dev, &hdr, dev->wd_data);
 	if (ret) {
 		dev_err(&dev->pdev->dev, "wd: write message failed\n");
 		return ret;
 	}

 	ret = mei_cl_flow_ctrl_reduce(cl);
 	if (ret) {
 		dev_err(&dev->pdev->dev, "wd: flow_ctrl_reduce failed.\n");
 		return ret;
 	}

 	return 0;
 }

 /**
  * mei_wd_stop - sends watchdog stop message to fw.
  *
  * @dev: the device structure
  * @preserve: indicate if to keep the timeout value
  *
  * returns 0 if success
  * on error:
  *	-EIO    when message send fails
  *	-EINVAL when invalid message is to be sent
  *	-ETIME  on message timeout
  */
 int mei_wd_stop(struct mei_device *dev)
 {
 	int ret;

 	if (dev->wd_cl.state != MEI_FILE_CONNECTED ||
 	    dev->wd_state != MEI_WD_RUNNING)
 		return 0;

 	memcpy(dev->wd_data, mei_stop_wd_params, MEI_WD_STOP_MSG_SIZE);

 	dev->wd_state = MEI_WD_STOPPING;

 	ret = mei_cl_flow_ctrl_creds(&dev->wd_cl);
 	if (ret < 0)
 		goto err;

 	if (ret && mei_hbuf_acquire(dev)) {
 		ret = mei_wd_send(dev);
 		if (ret)
 			goto err;
 		dev->wd_pending = false;
 	} else {
 		dev->wd_pending = true;
 	}

 	mutex_unlock(&dev->device_lock);

 	ret = wait_event_timeout(dev->wait_stop_wd,
 				dev->wd_state == MEI_WD_IDLE,
 				msecs_to_jiffies(MEI_WD_STOP_TIMEOUT));
 	mutex_lock(&dev->device_lock);
 	if (dev->wd_state != MEI_WD_IDLE) {
 		/* timeout */
 		ret = -ETIME;
 		dev_warn(&dev->pdev->dev,
 			"wd: stop failed to complete ret=%d.\n", ret);
 		goto err;
 	}
 	dev_dbg(&dev->pdev->dev, "wd: stop completed after %u msec\n",
 			MEI_WD_STOP_TIMEOUT - jiffies_to_msecs(ret));
 	return 0;
 err:
 	return ret;
 }

 /*
  * mei_wd_ops_start - wd start command from the watchdog core.
  *
  * @wd_dev - watchdog device struct
  *
  * returns 0 if success, negative errno code for failure
  */
 static int mei_wd_ops_start(struct watchdog_device *wd_dev)
 {
 	int err = -ENODEV;
 	struct mei_device *dev;

 	dev = watchdog_get_drvdata(wd_dev);
 	if (!dev)
 		return -ENODEV;

 	mutex_lock(&dev->device_lock);

 	if (dev->dev_state != MEI_DEV_ENABLED) {
 		dev_dbg(&dev->pdev->dev,
 			"wd: dev_state != MEI_DEV_ENABLED  dev_state = %s\n",
 			mei_dev_state_str(dev->dev_state));
 		goto end_unlock;
 	}

 	if (dev->wd_cl.state != MEI_FILE_CONNECTED)	{
 		dev_dbg(&dev->pdev->dev,
 			"MEI Driver is not connected to Watchdog Client\n");
 		goto end_unlock;
 	}

 	mei_wd_set_start_timeout(dev, dev->wd_timeout);

 	err = 0;
 end_unlock:
 	mutex_unlock(&dev->device_lock);
 	return err;
 }

 /*
  * mei_wd_ops_stop -  wd stop command from the watchdog core.
  *
  * @wd_dev - watchdog device struct
  *
  * returns 0 if success, negative errno code for failure
  */
 static int mei_wd_ops_stop(struct watchdog_device *wd_dev)
 {
 	struct mei_device *dev;

 	dev = watchdog_get_drvdata(wd_dev);
 	if (!dev)
 		return -ENODEV;

 	mutex_lock(&dev->device_lock);
 	mei_wd_stop(dev);
 	mutex_unlock(&dev->device_lock);

 	return 0;
 }

 /*
  * mei_wd_ops_ping - wd ping command from the watchdog core.
  *
  * @wd_dev - watchdog device struct
  *
  * returns 0 if success, negative errno code for failure
  */
 static int mei_wd_ops_ping(struct watchdog_device *wd_dev)
 {
 	struct mei_device *dev;
 	int ret;

 	dev = watchdog_get_drvdata(wd_dev);
 	if (!dev)
 		return -ENODEV;

 	mutex_lock(&dev->device_lock);

 	if (dev->wd_cl.state != MEI_FILE_CONNECTED) {
 		dev_err(&dev->pdev->dev, "wd: not connected.\n");
 		ret = -ENODEV;
 		goto end;
 	}

 	dev->wd_state = MEI_WD_RUNNING;

 	ret = mei_cl_flow_ctrl_creds(&dev->wd_cl);
 	if (ret < 0)
 		goto end;
 	/* Check if we can send the ping to HW*/
 	if (ret && mei_hbuf_acquire(dev)) {

 		dev_dbg(&dev->pdev->dev, "wd: sending ping\n");

 		ret = mei_wd_send(dev);
 		if (ret)
 			goto end;
 		dev->wd_pending = false;
 	} else {
 		dev->wd_pending = true;
 	}

 end:
 	mutex_unlock(&dev->device_lock);
 	return ret;
 }

 /*
  * mei_wd_ops_set_timeout - wd set timeout command from the watchdog core.
  *
  * @wd_dev - watchdog device struct
  * @timeout - timeout value to set
  *
  * returns 0 if success, negative errno code for failure
  */
 static int mei_wd_ops_set_timeout(struct watchdog_device *wd_dev,
 		unsigned int timeout)
 {
 	struct mei_device *dev;

 	dev = watchdog_get_drvdata(wd_dev);
 	if (!dev)
 		return -ENODEV;

 	/* Check Timeout value */
 	if (timeout < MEI_WD_MIN_TIMEOUT || timeout > MEI_WD_MAX_TIMEOUT)
 		return -EINVAL;

 	mutex_lock(&dev->device_lock);

 	dev->wd_timeout = timeout;
 	wd_dev->timeout = timeout;
 	mei_wd_set_start_timeout(dev, dev->wd_timeout);

 	mutex_unlock(&dev->device_lock);

 	return 0;
 }

 /*
  * Watchdog Device structs
  */
 static const struct watchdog_ops wd_ops = {
 		.owner = THIS_MODULE,
 		.start = mei_wd_ops_start,
 		.stop = mei_wd_ops_stop,
 		.ping = mei_wd_ops_ping,
 		.set_timeout = mei_wd_ops_set_timeout,
 };
 static const struct watchdog_info wd_info = {
 		.identity = INTEL_AMT_WATCHDOG_ID,
 		.options = WDIOF_KEEPALIVEPING |
 			   WDIOF_SETTIMEOUT |
 			   WDIOF_ALARMONLY,
 };

 static struct watchdog_device amt_wd_dev = {
 		.info = &wd_info,
 		.ops = &wd_ops,
 		.timeout = MEI_WD_DEFAULT_TIMEOUT,
 		.min_timeout = MEI_WD_MIN_TIMEOUT,
 		.max_timeout = MEI_WD_MAX_TIMEOUT,
 };


 int mei_watchdog_register(struct mei_device *dev)
 {

 	int ret;

 	/* unlock to perserve correct locking order */
 	mutex_unlock(&dev->device_lock);
 	ret = watchdog_register_device(&amt_wd_dev);
 	mutex_lock(&dev->device_lock);
 	if (ret) {
 		dev_err(&dev->pdev->dev, "wd: unable to register watchdog device = %d.\n",
 			ret);
 		return ret;
 	}

 	dev_dbg(&dev->pdev->dev,
 		"wd: successfully register watchdog interface.\n");
 	watchdog_set_drvdata(&amt_wd_dev, dev);
 	return 0;
 }

 void mei_watchdog_unregister(struct mei_device *dev)
 {
 	if (watchdog_get_drvdata(&amt_wd_dev) == NULL)
 		return;

 	watchdog_set_drvdata(&amt_wd_dev, NULL);
 	watchdog_unregister_device(&amt_wd_dev);
 }
	/*
	*
	* Intel Management Engine Interface (Intel MEI) Linux driver
	* Copyright (c) 2003-2012, Intel Corporation.
	*
	* This program is free software; you can redistribute it and/or modify it
	* under the terms and conditions of the GNU General Public License,
	* version 2, as published by the Free Software Foundation.
	*
	* This program is distributed in the hope 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/kernel.h>
	#include <linux/module.h>
	#include <linux/moduleparam.h>
	#include <linux/device.h>
	#include <linux/pci.h>
	#include <linux/sched.h>
	#include <linux/watchdog.h>

	#include <linux/mei.h>

	#include "mei_dev.h"
	#include "hbm.h"
	#include "client.h"

	static const u8 mei_start_wd_params[] = { 0x02, 0x12, 0x13, 0x10 };
	static const u8 mei_stop_wd_params[] = { 0x02, 0x02, 0x14, 0x10 };

	/*
	* AMT Watchdog Device
	*/
	#define INTEL_AMT_WATCHDOG_ID "INTCAMT"

	/* UUIDs for AMT F/W clients */
	const uuid_le mei_wd_guid = UUID_LE(0x05B79A6F, 0x4628, 0x4D7F, 0x89,
	0x9D, 0xA9, 0x15, 0x14, 0xCB,
	0x32, 0xAB);

	static void mei_wd_set_start_timeout(struct mei_device *dev, u16 timeout)
	{
	dev_dbg(&dev->pdev->dev, "wd: set timeout=%d.\n", timeout);
	memcpy(dev->wd_data, mei_start_wd_params, MEI_WD_HDR_SIZE);
	memcpy(dev->wd_data + MEI_WD_HDR_SIZE, &timeout, sizeof(u16));
	}

	/**
	* mei_wd_host_init - connect to the watchdog client
	*
	* @dev: the device structure
	*
	* returns -ENOTTY if wd client cannot be found
	* -EIO if write has failed
	* 0 on success
	*/
	int mei_wd_host_init(struct mei_device *dev)
	{
	struct mei_cl *cl = &dev->wd_cl;
	int id;
	int ret;

	mei_cl_init(cl, dev);

	dev->wd_timeout = MEI_WD_DEFAULT_TIMEOUT;
	dev->wd_state = MEI_WD_IDLE;


	/* check for valid client id */
	id = mei_me_cl_by_uuid(dev, &mei_wd_guid);
	if (id < 0) {
	dev_info(&dev->pdev->dev, "wd: failed to find the client\n");
	return -ENOTTY;
	}

	cl->me_client_id = dev->me_clients[id].client_id;

	ret = mei_cl_link(cl, MEI_WD_HOST_CLIENT_ID);

	if (ret < 0) {
	dev_info(&dev->pdev->dev, "wd: failed link client\n");
	return ret;
	}

	cl->state = MEI_FILE_CONNECTING;

	ret = mei_cl_connect(cl, NULL);

	if (ret) {
	dev_err(&dev->pdev->dev, "wd: failed to connect = %d\n", ret);
	mei_cl_unlink(cl);
	return ret;
	}

	ret = mei_watchdog_register(dev);
	if (ret) {
	mei_cl_disconnect(cl);
	mei_cl_unlink(cl);
	}
	return ret;
	}

	/**
	* mei_wd_send - sends watch dog message to fw.
	*
	* @dev: the device structure
	*
	* returns 0 if success,
	* -EIO when message send fails
	* -EINVAL when invalid message is to be sent
	* -ENODEV on flow control failure
	*/
	int mei_wd_send(struct mei_device *dev)
	{
	struct mei_cl *cl = &dev->wd_cl;
	struct mei_msg_hdr hdr;
	int ret;

	hdr.host_addr = cl->host_client_id;
	hdr.me_addr = cl->me_client_id;
	hdr.msg_complete = 1;
	hdr.reserved = 0;
	hdr.internal = 0;

	if (!memcmp(dev->wd_data, mei_start_wd_params, MEI_WD_HDR_SIZE))
	hdr.length = MEI_WD_START_MSG_SIZE;
	else if (!memcmp(dev->wd_data, mei_stop_wd_params, MEI_WD_HDR_SIZE))
	hdr.length = MEI_WD_STOP_MSG_SIZE;
	else {
	dev_err(&dev->pdev->dev, "wd: invalid message is to be sent, aborting\n");
	return -EINVAL;
	}

	ret = mei_write_message(dev, &hdr, dev->wd_data);
	if (ret) {
	dev_err(&dev->pdev->dev, "wd: write message failed\n");
	return ret;
	}

	ret = mei_cl_flow_ctrl_reduce(cl);
	if (ret) {
	dev_err(&dev->pdev->dev, "wd: flow_ctrl_reduce failed.\n");
	return ret;
	}

	return 0;
	}

	/**
	* mei_wd_stop - sends watchdog stop message to fw.
	*
	* @dev: the device structure
	* @preserve: indicate if to keep the timeout value
	*
	* returns 0 if success
	* on error:
	* -EIO when message send fails
	* -EINVAL when invalid message is to be sent
	* -ETIME on message timeout
	*/
	int mei_wd_stop(struct mei_device *dev)
	{
	int ret;

	if (dev->wd_cl.state != MEI_FILE_CONNECTED \|\|
	dev->wd_state != MEI_WD_RUNNING)
	return 0;

	memcpy(dev->wd_data, mei_stop_wd_params, MEI_WD_STOP_MSG_SIZE);

	dev->wd_state = MEI_WD_STOPPING;

	ret = mei_cl_flow_ctrl_creds(&dev->wd_cl);
	if (ret < 0)
	goto err;

	if (ret && mei_hbuf_acquire(dev)) {
	ret = mei_wd_send(dev);
	if (ret)
	goto err;
	dev->wd_pending = false;
	} else {
	dev->wd_pending = true;
	}

	mutex_unlock(&dev->device_lock);

	ret = wait_event_timeout(dev->wait_stop_wd,
	dev->wd_state == MEI_WD_IDLE,
	msecs_to_jiffies(MEI_WD_STOP_TIMEOUT));
	mutex_lock(&dev->device_lock);
	if (dev->wd_state != MEI_WD_IDLE) {
	/* timeout */
	ret = -ETIME;
	dev_warn(&dev->pdev->dev,
	"wd: stop failed to complete ret=%d.\n", ret);
	goto err;
	}
	dev_dbg(&dev->pdev->dev, "wd: stop completed after %u msec\n",
	MEI_WD_STOP_TIMEOUT - jiffies_to_msecs(ret));
	return 0;
	err:
	return ret;
	}

	/*
	* mei_wd_ops_start - wd start command from the watchdog core.
	*
	* @wd_dev - watchdog device struct
	*
	* returns 0 if success, negative errno code for failure
	*/
	static int mei_wd_ops_start(struct watchdog_device *wd_dev)
	{
	int err = -ENODEV;
	struct mei_device *dev;

	dev = watchdog_get_drvdata(wd_dev);
	if (!dev)
	return -ENODEV;

	mutex_lock(&dev->device_lock);

	if (dev->dev_state != MEI_DEV_ENABLED) {
	dev_dbg(&dev->pdev->dev,
	"wd: dev_state != MEI_DEV_ENABLED dev_state = %s\n",
	mei_dev_state_str(dev->dev_state));
	goto end_unlock;
	}

	if (dev->wd_cl.state != MEI_FILE_CONNECTED) {
	dev_dbg(&dev->pdev->dev,
	"MEI Driver is not connected to Watchdog Client\n");
	goto end_unlock;
	}

	mei_wd_set_start_timeout(dev, dev->wd_timeout);

	err = 0;
	end_unlock:
	mutex_unlock(&dev->device_lock);
	return err;
	}

	/*
	* mei_wd_ops_stop - wd stop command from the watchdog core.
	*
	* @wd_dev - watchdog device struct
	*
	* returns 0 if success, negative errno code for failure
	*/
	static int mei_wd_ops_stop(struct watchdog_device *wd_dev)
	{
	struct mei_device *dev;

	dev = watchdog_get_drvdata(wd_dev);
	if (!dev)
	return -ENODEV;

	mutex_lock(&dev->device_lock);
	mei_wd_stop(dev);
	mutex_unlock(&dev->device_lock);

	return 0;
	}

	/*
	* mei_wd_ops_ping - wd ping command from the watchdog core.
	*
	* @wd_dev - watchdog device struct
	*
	* returns 0 if success, negative errno code for failure
	*/
	static int mei_wd_ops_ping(struct watchdog_device *wd_dev)
	{
	struct mei_device *dev;
	int ret;

	dev = watchdog_get_drvdata(wd_dev);
	if (!dev)
	return -ENODEV;

	mutex_lock(&dev->device_lock);

	if (dev->wd_cl.state != MEI_FILE_CONNECTED) {
	dev_err(&dev->pdev->dev, "wd: not connected.\n");
	ret = -ENODEV;
	goto end;
	}

	dev->wd_state = MEI_WD_RUNNING;

	ret = mei_cl_flow_ctrl_creds(&dev->wd_cl);
	if (ret < 0)
	goto end;
	/* Check if we can send the ping to HW*/
	if (ret && mei_hbuf_acquire(dev)) {

	dev_dbg(&dev->pdev->dev, "wd: sending ping\n");

	ret = mei_wd_send(dev);
	if (ret)
	goto end;
	dev->wd_pending = false;
	} else {
	dev->wd_pending = true;
	}

	end:
	mutex_unlock(&dev->device_lock);
	return ret;
	}

	/*
	* mei_wd_ops_set_timeout - wd set timeout command from the watchdog core.
	*
	* @wd_dev - watchdog device struct
	* @timeout - timeout value to set
	*
	* returns 0 if success, negative errno code for failure
	*/
	static int mei_wd_ops_set_timeout(struct watchdog_device *wd_dev,
	unsigned int timeout)
	{
	struct mei_device *dev;

	dev = watchdog_get_drvdata(wd_dev);
	if (!dev)
	return -ENODEV;

	/* Check Timeout value */
	if (timeout < MEI_WD_MIN_TIMEOUT \|\| timeout > MEI_WD_MAX_TIMEOUT)
	return -EINVAL;

	mutex_lock(&dev->device_lock);

	dev->wd_timeout = timeout;
	wd_dev->timeout = timeout;
	mei_wd_set_start_timeout(dev, dev->wd_timeout);

	mutex_unlock(&dev->device_lock);

	return 0;
	}

	/*
	* Watchdog Device structs
	*/
	static const struct watchdog_ops wd_ops = {
	.owner = THIS_MODULE,
	.start = mei_wd_ops_start,
	.stop = mei_wd_ops_stop,
	.ping = mei_wd_ops_ping,
	.set_timeout = mei_wd_ops_set_timeout,
	};
	static const struct watchdog_info wd_info = {
	.identity = INTEL_AMT_WATCHDOG_ID,
	.options = WDIOF_KEEPALIVEPING \|
	WDIOF_SETTIMEOUT \|
	WDIOF_ALARMONLY,
	};

	static struct watchdog_device amt_wd_dev = {
	.info = &wd_info,
	.ops = &wd_ops,
	.timeout = MEI_WD_DEFAULT_TIMEOUT,
	.min_timeout = MEI_WD_MIN_TIMEOUT,
	.max_timeout = MEI_WD_MAX_TIMEOUT,
	};


	int mei_watchdog_register(struct mei_device *dev)
	{

	int ret;

	/* unlock to perserve correct locking order */
	mutex_unlock(&dev->device_lock);
	ret = watchdog_register_device(&amt_wd_dev);
	mutex_lock(&dev->device_lock);
	if (ret) {
	dev_err(&dev->pdev->dev, "wd: unable to register watchdog device = %d.\n",
	ret);
	return ret;
	}

	dev_dbg(&dev->pdev->dev,
	"wd: successfully register watchdog interface.\n");
	watchdog_set_drvdata(&amt_wd_dev, dev);
	return 0;
	}

	void mei_watchdog_unregister(struct mei_device *dev)
	{
	if (watchdog_get_drvdata(&amt_wd_dev) == NULL)
	return;

	watchdog_set_drvdata(&amt_wd_dev, NULL);
	watchdog_unregister_device(&amt_wd_dev);
	}