Adding upstream version 5.10.209.upstream/5.10.209

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

10 files changed, 1892 insertions, 0 deletions

diff --git a/Documentation/watchdog/convert_drivers_to_kernel_api.rst b/Documentation/watchdog/convert_drivers_to_kernel_api.rst
new file mode 100644
index 000000000..a1c3f038c
--- /dev/null
+++ b/Documentation/watchdog/convert_drivers_to_kernel_api.rst
@@ -0,0 +1,219 @@
+=========================================================
+Converting old watchdog drivers to the watchdog framework
+=========================================================
+
+by Wolfram Sang <wsa@kernel.org>
+
+Before the watchdog framework came into the kernel, every driver had to
+implement the API on its own. Now, as the framework factored out the common
+components, those drivers can be lightened making it a user of the framework.
+This document shall guide you for this task. The necessary steps are described
+as well as things to look out for.
+
+
+Remove the file_operations struct
+---------------------------------
+
+Old drivers define their own file_operations for actions like open(), write(),
+etc... These are now handled by the framework and just call the driver when
+needed. So, in general, the 'file_operations' struct and assorted functions can
+go. Only very few driver-specific details have to be moved to other functions.
+Here is a overview of the functions and probably needed actions:
+
+- open: Everything dealing with resource management (file-open checks, magic
+  close preparations) can simply go. Device specific stuff needs to go to the
+  driver specific start-function. Note that for some drivers, the start-function
+  also serves as the ping-function. If that is the case and you need start/stop
+  to be balanced (clocks!), you are better off refactoring a separate start-function.
+
+- close: Same hints as for open apply.
+
+- write: Can simply go, all defined behaviour is taken care of by the framework,
+  i.e. ping on write and magic char ('V') handling.
+
+- ioctl: While the driver is allowed to have extensions to the IOCTL interface,
+  the most common ones are handled by the framework, supported by some assistance
+  from the driver:
+
+	WDIOC_GETSUPPORT:
+		Returns the mandatory watchdog_info struct from the driver
+
+	WDIOC_GETSTATUS:
+		Needs the status-callback defined, otherwise returns 0
+
+	WDIOC_GETBOOTSTATUS:
+		Needs the bootstatus member properly set. Make sure it is 0 if you
+		don't have further support!
+
+	WDIOC_SETOPTIONS:
+		No preparations needed
+
+	WDIOC_KEEPALIVE:
+		If wanted, options in watchdog_info need to have WDIOF_KEEPALIVEPING
+		set
+
+	WDIOC_SETTIMEOUT:
+		Options in watchdog_info need to have WDIOF_SETTIMEOUT set
+		and a set_timeout-callback has to be defined. The core will also
+		do limit-checking, if min_timeout and max_timeout in the watchdog
+		device are set. All is optional.
+
+	WDIOC_GETTIMEOUT:
+		No preparations needed
+
+	WDIOC_GETTIMELEFT:
+		It needs get_timeleft() callback to be defined. Otherwise it
+		will return EOPNOTSUPP
+
+  Other IOCTLs can be served using the ioctl-callback. Note that this is mainly
+  intended for porting old drivers; new drivers should not invent private IOCTLs.
+  Private IOCTLs are processed first. When the callback returns with
+  -ENOIOCTLCMD, the IOCTLs of the framework will be tried, too. Any other error
+  is directly given to the user.
+
+Example conversion::
+
+  -static const struct file_operations s3c2410wdt_fops = {
+  -       .owner          = THIS_MODULE,
+  -       .llseek         = no_llseek,
+  -       .write          = s3c2410wdt_write,
+  -       .unlocked_ioctl = s3c2410wdt_ioctl,
+  -       .open           = s3c2410wdt_open,
+  -       .release        = s3c2410wdt_release,
+  -};
+
+Check the functions for device-specific stuff and keep it for later
+refactoring. The rest can go.
+
+
+Remove the miscdevice
+---------------------
+
+Since the file_operations are gone now, you can also remove the 'struct
+miscdevice'. The framework will create it on watchdog_dev_register() called by
+watchdog_register_device()::
+
+  -static struct miscdevice s3c2410wdt_miscdev = {
+  -       .minor          = WATCHDOG_MINOR,
+  -       .name           = "watchdog",
+  -       .fops           = &s3c2410wdt_fops,
+  -};
+
+
+Remove obsolete includes and defines
+------------------------------------
+
+Because of the simplifications, a few defines are probably unused now. Remove
+them. Includes can be removed, too. For example::
+
+  - #include <linux/fs.h>
+  - #include <linux/miscdevice.h> (if MODULE_ALIAS_MISCDEV is not used)
+  - #include <linux/uaccess.h> (if no custom IOCTLs are used)
+
+
+Add the watchdog operations
+---------------------------
+
+All possible callbacks are defined in 'struct watchdog_ops'. You can find it
+explained in 'watchdog-kernel-api.txt' in this directory. start() and
+owner must be set, the rest are optional. You will easily find corresponding
+functions in the old driver. Note that you will now get a pointer to the
+watchdog_device as a parameter to these functions, so you probably have to
+change the function header. Other changes are most likely not needed, because
+here simply happens the direct hardware access. If you have device-specific
+code left from the above steps, it should be refactored into these callbacks.
+
+Here is a simple example::
+
+  +static struct watchdog_ops s3c2410wdt_ops = {
+  +       .owner = THIS_MODULE,
+  +       .start = s3c2410wdt_start,
+  +       .stop = s3c2410wdt_stop,
+  +       .ping = s3c2410wdt_keepalive,
+  +       .set_timeout = s3c2410wdt_set_heartbeat,
+  +};
+
+A typical function-header change looks like::
+
+  -static void s3c2410wdt_keepalive(void)
+  +static int s3c2410wdt_keepalive(struct watchdog_device *wdd)
+   {
+  ...
+  +
+  +       return 0;
+   }
+
+  ...
+
+  -       s3c2410wdt_keepalive();
+  +       s3c2410wdt_keepalive(&s3c2410_wdd);
+
+
+Add the watchdog device
+-----------------------
+
+Now we need to create a 'struct watchdog_device' and populate it with the
+necessary information for the framework. The struct is also explained in detail
+in 'watchdog-kernel-api.txt' in this directory. We pass it the mandatory
+watchdog_info struct and the newly created watchdog_ops. Often, old drivers
+have their own record-keeping for things like bootstatus and timeout using
+static variables. Those have to be converted to use the members in
+watchdog_device. Note that the timeout values are unsigned int. Some drivers
+use signed int, so this has to be converted, too.
+
+Here is a simple example for a watchdog device::
+
+  +static struct watchdog_device s3c2410_wdd = {
+  +       .info = &s3c2410_wdt_ident,
+  +       .ops = &s3c2410wdt_ops,
+  +};
+
+
+Handle the 'nowayout' feature
+-----------------------------
+
+A few drivers use nowayout statically, i.e. there is no module parameter for it
+and only CONFIG_WATCHDOG_NOWAYOUT determines if the feature is going to be
+used. This needs to be converted by initializing the status variable of the
+watchdog_device like this::
+
+        .status = WATCHDOG_NOWAYOUT_INIT_STATUS,
+
+Most drivers, however, also allow runtime configuration of nowayout, usually
+by adding a module parameter. The conversion for this would be something like::
+
+	watchdog_set_nowayout(&s3c2410_wdd, nowayout);
+
+The module parameter itself needs to stay, everything else related to nowayout
+can go, though. This will likely be some code in open(), close() or write().
+
+
+Register the watchdog device
+----------------------------
+
+Replace misc_register(&miscdev) with watchdog_register_device(&watchdog_dev).
+Make sure the return value gets checked and the error message, if present,
+still fits. Also convert the unregister case::
+
+  -       ret = misc_register(&s3c2410wdt_miscdev);
+  +       ret = watchdog_register_device(&s3c2410_wdd);
+
+  ...
+
+  -       misc_deregister(&s3c2410wdt_miscdev);
+  +       watchdog_unregister_device(&s3c2410_wdd);
+
+
+Update the Kconfig-entry
+------------------------
+
+The entry for the driver now needs to select WATCHDOG_CORE:
+
+  +       select WATCHDOG_CORE
+
+
+Create a patch and send it to upstream
+--------------------------------------
+
+Make sure you understood Documentation/process/submitting-patches.rst and send your patch to
+linux-watchdog@vger.kernel.org. We are looking forward to it :)
diff --git a/Documentation/watchdog/hpwdt.rst b/Documentation/watchdog/hpwdt.rst
new file mode 100644
index 000000000..c824cd7f6
--- /dev/null
+++ b/Documentation/watchdog/hpwdt.rst
@@ -0,0 +1,77 @@
+===========================
+HPE iLO NMI Watchdog Driver
+===========================
+
+for iLO based ProLiant Servers
+==============================
+
+Last reviewed: 08/20/2018
+
+
+ The HPE iLO NMI Watchdog driver is a kernel module that provides basic
+ watchdog functionality and handler for the iLO "Generate NMI to System"
+ virtual button.
+
+ All references to iLO in this document imply it also works on iLO2 and all
+ subsequent generations.
+
+ Watchdog functionality is enabled like any other common watchdog driver. That
+ is, an application needs to be started that kicks off the watchdog timer. A
+ basic application exists in tools/testing/selftests/watchdog/ named
+ watchdog-test.c. Simply compile the C file and kick it off. If the system
+ gets into a bad state and hangs, the HPE ProLiant iLO timer register will
+ not be updated in a timely fashion and a hardware system reset (also known as
+ an Automatic Server Recovery (ASR)) event will occur.
+
+ The hpwdt driver also has the following module parameters:
+
+ ============  ================================================================
+ soft_margin   allows the user to set the watchdog timer value.
+               Default value is 30 seconds.
+ timeout       an alias of soft_margin.
+ pretimeout    allows the user to set the watchdog pretimeout value.
+               This is the number of seconds before timeout when an
+               NMI is delivered to the system. Setting the value to
+               zero disables the pretimeout NMI.
+               Default value is 9 seconds.
+ nowayout      basic watchdog parameter that does not allow the timer to
+               be restarted or an impending ASR to be escaped.
+               Default value is set when compiling the kernel. If it is set
+               to "Y", then there is no way of disabling the watchdog once
+               it has been started.
+ kdumptimeout  Minimum timeout in seconds to apply upon receipt of an NMI
+               before calling panic. (-1) disables the watchdog.  When value
+               is > 0, the timer is reprogrammed with the greater of
+               value or current timeout value.
+ ============  ================================================================
+
+ NOTE:
+       More information about watchdog drivers in general, including the ioctl
+       interface to /dev/watchdog can be found in
+       Documentation/watchdog/watchdog-api.rst and Documentation/IPMI.txt.
+
+ Due to limitations in the iLO hardware, the NMI pretimeout if enabled,
+ can only be set to 9 seconds.  Attempts to set pretimeout to other
+ non-zero values will be rounded, possibly to zero.  Users should verify
+ the pretimeout value after attempting to set pretimeout or timeout.
+
+ Upon receipt of an NMI from the iLO, the hpwdt driver will initiate a
+ panic. This is to allow for a crash dump to be collected.  It is incumbent
+ upon the user to have properly configured the system for kdump.
+
+ The default Linux kernel behavior upon panic is to print a kernel tombstone
+ and loop forever.  This is generally not what a watchdog user wants.
+
+ For those wishing to learn more please see:
+	Documentation/admin-guide/kdump/kdump.rst
+	Documentation/admin-guide/kernel-parameters.txt (panic=)
+	Your Linux Distribution specific documentation.
+
+ If the hpwdt does not receive the NMI associated with an expiring timer,
+ the iLO will proceed to reset the system at timeout if the timer hasn't
+ been updated.
+
+--
+
+ The HPE iLO NMI Watchdog Driver and documentation were originally developed
+ by Tom Mingarelli.
diff --git a/Documentation/watchdog/index.rst b/Documentation/watchdog/index.rst
new file mode 100644
index 000000000..c17764508
--- /dev/null
+++ b/Documentation/watchdog/index.rst
@@ -0,0 +1,25 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+======================
+Linux Watchdog Support
+======================
+
+.. toctree::
+    :maxdepth: 1
+
+    hpwdt
+    mlx-wdt
+    pcwd-watchdog
+    watchdog-api
+    watchdog-kernel-api
+    watchdog-parameters
+    watchdog-pm
+    wdt
+    convert_drivers_to_kernel_api
+
+.. only::  subproject and html
+
+   Indices
+   =======
+
+   * :ref:`genindex`
diff --git a/Documentation/watchdog/mlx-wdt.rst b/Documentation/watchdog/mlx-wdt.rst
new file mode 100644
index 000000000..35e690dea
--- /dev/null
+++ b/Documentation/watchdog/mlx-wdt.rst
@@ -0,0 +1,66 @@
+=========================
+Mellanox watchdog drivers
+=========================
+
+for x86 based system switches
+=============================
+
+This driver provides watchdog functionality for various Mellanox
+Ethernet and Infiniband switch systems.
+
+Mellanox watchdog device is implemented in a programmable logic device.
+
+There are 2 types of HW watchdog implementations.
+
+Type 1:
+  Actual HW timeout can be defined as a power of 2 msec.
+  e.g. timeout 20 sec will be rounded up to 32768 msec.
+  The maximum timeout period is 32 sec (32768 msec.),
+  Get time-left isn't supported
+
+Type 2:
+  Actual HW timeout is defined in sec. and it's the same as
+  a user-defined timeout.
+  Maximum timeout is 255 sec.
+  Get time-left is supported.
+
+Type 3:
+  Same as Type 2 with extended maximum timeout period.
+  Maximum timeout is 65535 sec.
+
+Type 1 HW watchdog implementation exist in old systems and
+all new systems have type 2 HW watchdog.
+Two types of HW implementation have also different register map.
+
+Type 3 HW watchdog implementation can exist on all Mellanox systems
+with new programmer logic device.
+It's differentiated by WD capability bit.
+Old systems still have only one main watchdog.
+
+Mellanox system can have 2 watchdogs: main and auxiliary.
+Main and auxiliary watchdog devices can be enabled together
+on the same system.
+There are several actions that can be defined in the watchdog:
+system reset, start fans on full speed and increase register counter.
+The last 2 actions are performed without a system reset.
+Actions without reset are provided for auxiliary watchdog device,
+which is optional.
+Watchdog can be started during a probe, in this case it will be
+pinged by watchdog core before watchdog device will be opened by
+user space application.
+Watchdog can be initialised in nowayout way, i.e. oncse started
+it can't be stopped.
+
+This mlx-wdt driver supports both HW watchdog implementations.
+
+Watchdog driver is probed from the common mlx_platform driver.
+Mlx_platform driver provides an appropriate set of registers for
+Mellanox watchdog device, identity name (mlx-wdt-main or mlx-wdt-aux),
+initial timeout, performed action in expiration and configuration flags.
+watchdog configuration flags: nowayout and start_at_boot, hw watchdog
+version - type1 or type2.
+The driver checks during initialization if the previous system reset
+was done by the watchdog. If yes, it makes a notification about this event.
+
+Access to HW registers is performed through a generic regmap interface.
+Programmable logic device registers have little-endian order.
diff --git a/Documentation/watchdog/pcwd-watchdog.rst b/Documentation/watchdog/pcwd-watchdog.rst
new file mode 100644
index 000000000..405e2a370
--- /dev/null
+++ b/Documentation/watchdog/pcwd-watchdog.rst
@@ -0,0 +1,71 @@
+===================================
+Berkshire Products PC Watchdog Card
+===================================
+
+Last reviewed: 10/05/2007
+
+Support for ISA Cards  Revision A and C
+=======================================
+
+Documentation and Driver by Ken Hollis <kenji@bitgate.com>
+
+ The PC Watchdog is a card that offers the same type of functionality that
+ the WDT card does, only it doesn't require an IRQ to run.  Furthermore,
+ the Revision C card allows you to monitor any IO Port to automatically
+ trigger the card into being reset.  This way you can make the card
+ monitor hard drive status, or anything else you need.
+
+ The Watchdog Driver has one basic role: to talk to the card and send
+ signals to it so it doesn't reset your computer ... at least during
+ normal operation.
+
+ The Watchdog Driver will automatically find your watchdog card, and will
+ attach a running driver for use with that card.  After the watchdog
+ drivers have initialized, you can then talk to the card using a PC
+ Watchdog program.
+
+ I suggest putting a "watchdog -d" before the beginning of an fsck, and
+ a "watchdog -e -t 1" immediately after the end of an fsck.  (Remember
+ to run the program with an "&" to run it in the background!)
+
+ If you want to write a program to be compatible with the PC Watchdog
+ driver, simply use of modify the watchdog test program:
+ tools/testing/selftests/watchdog/watchdog-test.c
+
+
+ Other IOCTL functions include:
+
+	WDIOC_GETSUPPORT
+		This returns the support of the card itself.  This
+		returns in structure "PCWDS" which returns:
+
+			options = WDIOS_TEMPPANIC
+				  (This card supports temperature)
+			firmware_version = xxxx
+				  (Firmware version of the card)
+
+	WDIOC_GETSTATUS
+		This returns the status of the card, with the bits of
+		WDIOF_* bitwise-anded into the value.  (The comments
+		are in linux/pcwd.h)
+
+	WDIOC_GETBOOTSTATUS
+		This returns the status of the card that was reported
+		at bootup.
+
+	WDIOC_GETTEMP
+		This returns the temperature of the card.  (You can also
+		read /dev/watchdog, which gives a temperature update
+		every second.)
+
+	WDIOC_SETOPTIONS
+		This lets you set the options of the card.  You can either
+		enable or disable the card this way.
+
+	WDIOC_KEEPALIVE
+		This pings the card to tell it not to reset your computer.
+
+ And that's all she wrote!
+
+ -- Ken Hollis
+    (kenji@bitgate.com)
diff --git a/Documentation/watchdog/watchdog-api.rst b/Documentation/watchdog/watchdog-api.rst
new file mode 100644
index 000000000..800dcd758
--- /dev/null
+++ b/Documentation/watchdog/watchdog-api.rst
@@ -0,0 +1,271 @@
+=============================
+The Linux Watchdog driver API
+=============================
+
+Last reviewed: 10/05/2007
+
+
+
+Copyright 2002 Christer Weingel <wingel@nano-system.com>
+
+Some parts of this document are copied verbatim from the sbc60xxwdt
+driver which is (c) Copyright 2000 Jakob Oestergaard <jakob@ostenfeld.dk>
+
+This document describes the state of the Linux 2.4.18 kernel.
+
+Introduction
+============
+
+A Watchdog Timer (WDT) is a hardware circuit that can reset the
+computer system in case of a software fault.  You probably knew that
+already.
+
+Usually a userspace daemon will notify the kernel watchdog driver via the
+/dev/watchdog special device file that userspace is still alive, at
+regular intervals.  When such a notification occurs, the driver will
+usually tell the hardware watchdog that everything is in order, and
+that the watchdog should wait for yet another little while to reset
+the system.  If userspace fails (RAM error, kernel bug, whatever), the
+notifications cease to occur, and the hardware watchdog will reset the
+system (causing a reboot) after the timeout occurs.
+
+The Linux watchdog API is a rather ad-hoc construction and different
+drivers implement different, and sometimes incompatible, parts of it.
+This file is an attempt to document the existing usage and allow
+future driver writers to use it as a reference.
+
+The simplest API
+================
+
+All drivers support the basic mode of operation, where the watchdog
+activates as soon as /dev/watchdog is opened and will reboot unless
+the watchdog is pinged within a certain time, this time is called the
+timeout or margin.  The simplest way to ping the watchdog is to write
+some data to the device.  So a very simple watchdog daemon would look
+like this source file:  see samples/watchdog/watchdog-simple.c
+
+A more advanced driver could for example check that a HTTP server is
+still responding before doing the write call to ping the watchdog.
+
+When the device is closed, the watchdog is disabled, unless the "Magic
+Close" feature is supported (see below).  This is not always such a
+good idea, since if there is a bug in the watchdog daemon and it
+crashes the system will not reboot.  Because of this, some of the
+drivers support the configuration option "Disable watchdog shutdown on
+close", CONFIG_WATCHDOG_NOWAYOUT.  If it is set to Y when compiling
+the kernel, there is no way of disabling the watchdog once it has been
+started.  So, if the watchdog daemon crashes, the system will reboot
+after the timeout has passed. Watchdog devices also usually support
+the nowayout module parameter so that this option can be controlled at
+runtime.
+
+Magic Close feature
+===================
+
+If a driver supports "Magic Close", the driver will not disable the
+watchdog unless a specific magic character 'V' has been sent to
+/dev/watchdog just before closing the file.  If the userspace daemon
+closes the file without sending this special character, the driver
+will assume that the daemon (and userspace in general) died, and will
+stop pinging the watchdog without disabling it first.  This will then
+cause a reboot if the watchdog is not re-opened in sufficient time.
+
+The ioctl API
+=============
+
+All conforming drivers also support an ioctl API.
+
+Pinging the watchdog using an ioctl:
+
+All drivers that have an ioctl interface support at least one ioctl,
+KEEPALIVE.  This ioctl does exactly the same thing as a write to the
+watchdog device, so the main loop in the above program could be
+replaced with::
+
+	while (1) {
+		ioctl(fd, WDIOC_KEEPALIVE, 0);
+		sleep(10);
+	}
+
+the argument to the ioctl is ignored.
+
+Setting and getting the timeout
+===============================
+
+For some drivers it is possible to modify the watchdog timeout on the
+fly with the SETTIMEOUT ioctl, those drivers have the WDIOF_SETTIMEOUT
+flag set in their option field.  The argument is an integer
+representing the timeout in seconds.  The driver returns the real
+timeout used in the same variable, and this timeout might differ from
+the requested one due to limitation of the hardware::
+
+    int timeout = 45;
+    ioctl(fd, WDIOC_SETTIMEOUT, &timeout);
+    printf("The timeout was set to %d seconds\n", timeout);
+
+This example might actually print "The timeout was set to 60 seconds"
+if the device has a granularity of minutes for its timeout.
+
+Starting with the Linux 2.4.18 kernel, it is possible to query the
+current timeout using the GETTIMEOUT ioctl::
+
+    ioctl(fd, WDIOC_GETTIMEOUT, &timeout);
+    printf("The timeout was is %d seconds\n", timeout);
+
+Pretimeouts
+===========
+
+Some watchdog timers can be set to have a trigger go off before the
+actual time they will reset the system.  This can be done with an NMI,
+interrupt, or other mechanism.  This allows Linux to record useful
+information (like panic information and kernel coredumps) before it
+resets::
+
+    pretimeout = 10;
+    ioctl(fd, WDIOC_SETPRETIMEOUT, &pretimeout);
+
+Note that the pretimeout is the number of seconds before the time
+when the timeout will go off.  It is not the number of seconds until
+the pretimeout.  So, for instance, if you set the timeout to 60 seconds
+and the pretimeout to 10 seconds, the pretimeout will go off in 50
+seconds.  Setting a pretimeout to zero disables it.
+
+There is also a get function for getting the pretimeout::
+
+    ioctl(fd, WDIOC_GETPRETIMEOUT, &timeout);
+    printf("The pretimeout was is %d seconds\n", timeout);
+
+Not all watchdog drivers will support a pretimeout.
+
+Get the number of seconds before reboot
+=======================================
+
+Some watchdog drivers have the ability to report the remaining time
+before the system will reboot. The WDIOC_GETTIMELEFT is the ioctl
+that returns the number of seconds before reboot::
+
+    ioctl(fd, WDIOC_GETTIMELEFT, &timeleft);
+    printf("The timeout was is %d seconds\n", timeleft);
+
+Environmental monitoring
+========================
+
+All watchdog drivers are required return more information about the system,
+some do temperature, fan and power level monitoring, some can tell you
+the reason for the last reboot of the system.  The GETSUPPORT ioctl is
+available to ask what the device can do::
+
+	struct watchdog_info ident;
+	ioctl(fd, WDIOC_GETSUPPORT, &ident);
+
+the fields returned in the ident struct are:
+
+	================	=============================================
+        identity		a string identifying the watchdog driver
+	firmware_version	the firmware version of the card if available
+	options			a flags describing what the device supports
+	================	=============================================
+
+the options field can have the following bits set, and describes what
+kind of information that the GET_STATUS and GET_BOOT_STATUS ioctls can
+return.
+
+	================	=========================
+	WDIOF_OVERHEAT		Reset due to CPU overheat
+	================	=========================
+
+The machine was last rebooted by the watchdog because the thermal limit was
+exceeded:
+
+	==============		==========
+	WDIOF_FANFAULT		Fan failed
+	==============		==========
+
+A system fan monitored by the watchdog card has failed
+
+	=============		================
+	WDIOF_EXTERN1		External relay 1
+	=============		================
+
+External monitoring relay/source 1 was triggered. Controllers intended for
+real world applications include external monitoring pins that will trigger
+a reset.
+
+	=============		================
+	WDIOF_EXTERN2		External relay 2
+	=============		================
+
+External monitoring relay/source 2 was triggered
+
+	================	=====================
+	WDIOF_POWERUNDER	Power bad/power fault
+	================	=====================
+
+The machine is showing an undervoltage status
+
+	===============		=============================
+	WDIOF_CARDRESET		Card previously reset the CPU
+	===============		=============================
+
+The last reboot was caused by the watchdog card
+
+	================	=====================
+	WDIOF_POWEROVER		Power over voltage
+	================	=====================
+
+The machine is showing an overvoltage status. Note that if one level is
+under and one over both bits will be set - this may seem odd but makes
+sense.
+
+	===================	=====================
+	WDIOF_KEEPALIVEPING	Keep alive ping reply
+	===================	=====================
+
+The watchdog saw a keepalive ping since it was last queried.
+
+	================	=======================
+	WDIOF_SETTIMEOUT	Can set/get the timeout
+	================	=======================
+
+The watchdog can do pretimeouts.
+
+	================	================================
+	WDIOF_PRETIMEOUT	Pretimeout (in seconds), get/set
+	================	================================
+
+
+For those drivers that return any bits set in the option field, the
+GETSTATUS and GETBOOTSTATUS ioctls can be used to ask for the current
+status, and the status at the last reboot, respectively::
+
+    int flags;
+    ioctl(fd, WDIOC_GETSTATUS, &flags);
+
+    or
+
+    ioctl(fd, WDIOC_GETBOOTSTATUS, &flags);
+
+Note that not all devices support these two calls, and some only
+support the GETBOOTSTATUS call.
+
+Some drivers can measure the temperature using the GETTEMP ioctl.  The
+returned value is the temperature in degrees fahrenheit::
+
+    int temperature;
+    ioctl(fd, WDIOC_GETTEMP, &temperature);
+
+Finally the SETOPTIONS ioctl can be used to control some aspects of
+the cards operation::
+
+    int options = 0;
+    ioctl(fd, WDIOC_SETOPTIONS, &options);
+
+The following options are available:
+
+	=================	================================
+	WDIOS_DISABLECARD	Turn off the watchdog timer
+	WDIOS_ENABLECARD	Turn on the watchdog timer
+	WDIOS_TEMPPANIC		Kernel panic on temperature trip
+	=================	================================
+
+[FIXME -- better explanations]
diff --git a/Documentation/watchdog/watchdog-kernel-api.rst b/Documentation/watchdog/watchdog-kernel-api.rst
new file mode 100644
index 000000000..baf44e986
--- /dev/null
+++ b/Documentation/watchdog/watchdog-kernel-api.rst
@@ -0,0 +1,350 @@
+===============================================
+The Linux WatchDog Timer Driver Core kernel API
+===============================================
+
+Last reviewed: 12-Feb-2013
+
+Wim Van Sebroeck <wim@iguana.be>
+
+Introduction
+------------
+This document does not describe what a WatchDog Timer (WDT) Driver or Device is.
+It also does not describe the API which can be used by user space to communicate
+with a WatchDog Timer. If you want to know this then please read the following
+file: Documentation/watchdog/watchdog-api.rst .
+
+So what does this document describe? It describes the API that can be used by
+WatchDog Timer Drivers that want to use the WatchDog Timer Driver Core
+Framework. This framework provides all interfacing towards user space so that
+the same code does not have to be reproduced each time. This also means that
+a watchdog timer driver then only needs to provide the different routines
+(operations) that control the watchdog timer (WDT).
+
+The API
+-------
+Each watchdog timer driver that wants to use the WatchDog Timer Driver Core
+must #include <linux/watchdog.h> (you would have to do this anyway when
+writing a watchdog device driver). This include file contains following
+register/unregister routines::
+
+	extern int watchdog_register_device(struct watchdog_device *);
+	extern void watchdog_unregister_device(struct watchdog_device *);
+
+The watchdog_register_device routine registers a watchdog timer device.
+The parameter of this routine is a pointer to a watchdog_device structure.
+This routine returns zero on success and a negative errno code for failure.
+
+The watchdog_unregister_device routine deregisters a registered watchdog timer
+device. The parameter of this routine is the pointer to the registered
+watchdog_device structure.
+
+The watchdog subsystem includes an registration deferral mechanism,
+which allows you to register an watchdog as early as you wish during
+the boot process.
+
+The watchdog device structure looks like this::
+
+  struct watchdog_device {
+	int id;
+	struct device *parent;
+	const struct attribute_group **groups;
+	const struct watchdog_info *info;
+	const struct watchdog_ops *ops;
+	const struct watchdog_governor *gov;
+	unsigned int bootstatus;
+	unsigned int timeout;
+	unsigned int pretimeout;
+	unsigned int min_timeout;
+	unsigned int max_timeout;
+	unsigned int min_hw_heartbeat_ms;
+	unsigned int max_hw_heartbeat_ms;
+	struct notifier_block reboot_nb;
+	struct notifier_block restart_nb;
+	void *driver_data;
+	struct watchdog_core_data *wd_data;
+	unsigned long status;
+	struct list_head deferred;
+  };
+
+It contains following fields:
+
+* id: set by watchdog_register_device, id 0 is special. It has both a
+  /dev/watchdog0 cdev (dynamic major, minor 0) as well as the old
+  /dev/watchdog miscdev. The id is set automatically when calling
+  watchdog_register_device.
+* parent: set this to the parent device (or NULL) before calling
+  watchdog_register_device.
+* groups: List of sysfs attribute groups to create when creating the watchdog
+  device.
+* info: a pointer to a watchdog_info structure. This structure gives some
+  additional information about the watchdog timer itself. (Like it's unique name)
+* ops: a pointer to the list of watchdog operations that the watchdog supports.
+* gov: a pointer to the assigned watchdog device pretimeout governor or NULL.
+* timeout: the watchdog timer's timeout value (in seconds).
+  This is the time after which the system will reboot if user space does
+  not send a heartbeat request if WDOG_ACTIVE is set.
+* pretimeout: the watchdog timer's pretimeout value (in seconds).
+* min_timeout: the watchdog timer's minimum timeout value (in seconds).
+  If set, the minimum configurable value for 'timeout'.
+* max_timeout: the watchdog timer's maximum timeout value (in seconds),
+  as seen from userspace. If set, the maximum configurable value for
+  'timeout'. Not used if max_hw_heartbeat_ms is non-zero.
+* min_hw_heartbeat_ms: Hardware limit for minimum time between heartbeats,
+  in milli-seconds. This value is normally 0; it should only be provided
+  if the hardware can not tolerate lower intervals between heartbeats.
+* max_hw_heartbeat_ms: Maximum hardware heartbeat, in milli-seconds.
+  If set, the infrastructure will send heartbeats to the watchdog driver
+  if 'timeout' is larger than max_hw_heartbeat_ms, unless WDOG_ACTIVE
+  is set and userspace failed to send a heartbeat for at least 'timeout'
+  seconds. max_hw_heartbeat_ms must be set if a driver does not implement
+  the stop function.
+* reboot_nb: notifier block that is registered for reboot notifications, for
+  internal use only. If the driver calls watchdog_stop_on_reboot, watchdog core
+  will stop the watchdog on such notifications.
+* restart_nb: notifier block that is registered for machine restart, for
+  internal use only. If a watchdog is capable of restarting the machine, it
+  should define ops->restart. Priority can be changed through
+  watchdog_set_restart_priority.
+* bootstatus: status of the device after booting (reported with watchdog
+  WDIOF_* status bits).
+* driver_data: a pointer to the drivers private data of a watchdog device.
+  This data should only be accessed via the watchdog_set_drvdata and
+  watchdog_get_drvdata routines.
+* wd_data: a pointer to watchdog core internal data.
+* status: this field contains a number of status bits that give extra
+  information about the status of the device (Like: is the watchdog timer
+  running/active, or is the nowayout bit set).
+* deferred: entry in wtd_deferred_reg_list which is used to
+  register early initialized watchdogs.
+
+The list of watchdog operations is defined as::
+
+  struct watchdog_ops {
+	struct module *owner;
+	/* mandatory operations */
+	int (*start)(struct watchdog_device *);
+	/* optional operations */
+	int (*stop)(struct watchdog_device *);
+	int (*ping)(struct watchdog_device *);
+	unsigned int (*status)(struct watchdog_device *);
+	int (*set_timeout)(struct watchdog_device *, unsigned int);
+	int (*set_pretimeout)(struct watchdog_device *, unsigned int);
+	unsigned int (*get_timeleft)(struct watchdog_device *);
+	int (*restart)(struct watchdog_device *);
+	long (*ioctl)(struct watchdog_device *, unsigned int, unsigned long);
+  };
+
+It is important that you first define the module owner of the watchdog timer
+driver's operations. This module owner will be used to lock the module when
+the watchdog is active. (This to avoid a system crash when you unload the
+module and /dev/watchdog is still open).
+
+Some operations are mandatory and some are optional. The mandatory operations
+are:
+
+* start: this is a pointer to the routine that starts the watchdog timer
+  device.
+  The routine needs a pointer to the watchdog timer device structure as a
+  parameter. It returns zero on success or a negative errno code for failure.
+
+Not all watchdog timer hardware supports the same functionality. That's why
+all other routines/operations are optional. They only need to be provided if
+they are supported. These optional routines/operations are:
+
+* stop: with this routine the watchdog timer device is being stopped.
+
+  The routine needs a pointer to the watchdog timer device structure as a
+  parameter. It returns zero on success or a negative errno code for failure.
+  Some watchdog timer hardware can only be started and not be stopped. A
+  driver supporting such hardware does not have to implement the stop routine.
+
+  If a driver has no stop function, the watchdog core will set WDOG_HW_RUNNING
+  and start calling the driver's keepalive pings function after the watchdog
+  device is closed.
+
+  If a watchdog driver does not implement the stop function, it must set
+  max_hw_heartbeat_ms.
+* ping: this is the routine that sends a keepalive ping to the watchdog timer
+  hardware.
+
+  The routine needs a pointer to the watchdog timer device structure as a
+  parameter. It returns zero on success or a negative errno code for failure.
+
+  Most hardware that does not support this as a separate function uses the
+  start function to restart the watchdog timer hardware. And that's also what
+  the watchdog timer driver core does: to send a keepalive ping to the watchdog
+  timer hardware it will either use the ping operation (when available) or the
+  start operation (when the ping operation is not available).
+
+  (Note: the WDIOC_KEEPALIVE ioctl call will only be active when the
+  WDIOF_KEEPALIVEPING bit has been set in the option field on the watchdog's
+  info structure).
+* status: this routine checks the status of the watchdog timer device. The
+  status of the device is reported with watchdog WDIOF_* status flags/bits.
+
+  WDIOF_MAGICCLOSE and WDIOF_KEEPALIVEPING are reported by the watchdog core;
+  it is not necessary to report those bits from the driver. Also, if no status
+  function is provided by the driver, the watchdog core reports the status bits
+  provided in the bootstatus variable of struct watchdog_device.
+
+* set_timeout: this routine checks and changes the timeout of the watchdog
+  timer device. It returns 0 on success, -EINVAL for "parameter out of range"
+  and -EIO for "could not write value to the watchdog". On success this
+  routine should set the timeout value of the watchdog_device to the
+  achieved timeout value (which may be different from the requested one
+  because the watchdog does not necessarily have a 1 second resolution).
+
+  Drivers implementing max_hw_heartbeat_ms set the hardware watchdog heartbeat
+  to the minimum of timeout and max_hw_heartbeat_ms. Those drivers set the
+  timeout value of the watchdog_device either to the requested timeout value
+  (if it is larger than max_hw_heartbeat_ms), or to the achieved timeout value.
+  (Note: the WDIOF_SETTIMEOUT needs to be set in the options field of the
+  watchdog's info structure).
+
+  If the watchdog driver does not have to perform any action but setting the
+  watchdog_device.timeout, this callback can be omitted.
+
+  If set_timeout is not provided but, WDIOF_SETTIMEOUT is set, the watchdog
+  infrastructure updates the timeout value of the watchdog_device internally
+  to the requested value.
+
+  If the pretimeout feature is used (WDIOF_PRETIMEOUT), then set_timeout must
+  also take care of checking if pretimeout is still valid and set up the timer
+  accordingly. This can't be done in the core without races, so it is the
+  duty of the driver.
+* set_pretimeout: this routine checks and changes the pretimeout value of
+  the watchdog. It is optional because not all watchdogs support pretimeout
+  notification. The timeout value is not an absolute time, but the number of
+  seconds before the actual timeout would happen. It returns 0 on success,
+  -EINVAL for "parameter out of range" and -EIO for "could not write value to
+  the watchdog". A value of 0 disables pretimeout notification.
+
+  (Note: the WDIOF_PRETIMEOUT needs to be set in the options field of the
+  watchdog's info structure).
+
+  If the watchdog driver does not have to perform any action but setting the
+  watchdog_device.pretimeout, this callback can be omitted. That means if
+  set_pretimeout is not provided but WDIOF_PRETIMEOUT is set, the watchdog
+  infrastructure updates the pretimeout value of the watchdog_device internally
+  to the requested value.
+
+* get_timeleft: this routines returns the time that's left before a reset.
+* restart: this routine restarts the machine. It returns 0 on success or a
+  negative errno code for failure.
+* ioctl: if this routine is present then it will be called first before we do
+  our own internal ioctl call handling. This routine should return -ENOIOCTLCMD
+  if a command is not supported. The parameters that are passed to the ioctl
+  call are: watchdog_device, cmd and arg.
+
+The status bits should (preferably) be set with the set_bit and clear_bit alike
+bit-operations. The status bits that are defined are:
+
+* WDOG_ACTIVE: this status bit indicates whether or not a watchdog timer device
+  is active or not from user perspective. User space is expected to send
+  heartbeat requests to the driver while this flag is set.
+* WDOG_NO_WAY_OUT: this bit stores the nowayout setting for the watchdog.
+  If this bit is set then the watchdog timer will not be able to stop.
+* WDOG_HW_RUNNING: Set by the watchdog driver if the hardware watchdog is
+  running. The bit must be set if the watchdog timer hardware can not be
+  stopped. The bit may also be set if the watchdog timer is running after
+  booting, before the watchdog device is opened. If set, the watchdog
+  infrastructure will send keepalives to the watchdog hardware while
+  WDOG_ACTIVE is not set.
+  Note: when you register the watchdog timer device with this bit set,
+  then opening /dev/watchdog will skip the start operation but send a keepalive
+  request instead.
+
+  To set the WDOG_NO_WAY_OUT status bit (before registering your watchdog
+  timer device) you can either:
+
+  * set it statically in your watchdog_device struct with
+
+	.status = WATCHDOG_NOWAYOUT_INIT_STATUS,
+
+    (this will set the value the same as CONFIG_WATCHDOG_NOWAYOUT) or
+  * use the following helper function::
+
+	static inline void watchdog_set_nowayout(struct watchdog_device *wdd,
+						 int nowayout)
+
+Note:
+   The WatchDog Timer Driver Core supports the magic close feature and
+   the nowayout feature. To use the magic close feature you must set the
+   WDIOF_MAGICCLOSE bit in the options field of the watchdog's info structure.
+
+The nowayout feature will overrule the magic close feature.
+
+To get or set driver specific data the following two helper functions should be
+used::
+
+  static inline void watchdog_set_drvdata(struct watchdog_device *wdd,
+					  void *data)
+  static inline void *watchdog_get_drvdata(struct watchdog_device *wdd)
+
+The watchdog_set_drvdata function allows you to add driver specific data. The
+arguments of this function are the watchdog device where you want to add the
+driver specific data to and a pointer to the data itself.
+
+The watchdog_get_drvdata function allows you to retrieve driver specific data.
+The argument of this function is the watchdog device where you want to retrieve
+data from. The function returns the pointer to the driver specific data.
+
+To initialize the timeout field, the following function can be used::
+
+  extern int watchdog_init_timeout(struct watchdog_device *wdd,
+                                   unsigned int timeout_parm,
+                                   struct device *dev);
+
+The watchdog_init_timeout function allows you to initialize the timeout field
+using the module timeout parameter or by retrieving the timeout-sec property from
+the device tree (if the module timeout parameter is invalid). Best practice is
+to set the default timeout value as timeout value in the watchdog_device and
+then use this function to set the user "preferred" timeout value.
+This routine returns zero on success and a negative errno code for failure.
+
+To disable the watchdog on reboot, the user must call the following helper::
+
+  static inline void watchdog_stop_on_reboot(struct watchdog_device *wdd);
+
+To disable the watchdog when unregistering the watchdog, the user must call
+the following helper. Note that this will only stop the watchdog if the
+nowayout flag is not set.
+
+::
+
+  static inline void watchdog_stop_on_unregister(struct watchdog_device *wdd);
+
+To change the priority of the restart handler the following helper should be
+used::
+
+  void watchdog_set_restart_priority(struct watchdog_device *wdd, int priority);
+
+User should follow the following guidelines for setting the priority:
+
+* 0: should be called in last resort, has limited restart capabilities
+* 128: default restart handler, use if no other handler is expected to be
+  available, and/or if restart is sufficient to restart the entire system
+* 255: highest priority, will preempt all other restart handlers
+
+To raise a pretimeout notification, the following function should be used::
+
+  void watchdog_notify_pretimeout(struct watchdog_device *wdd)
+
+The function can be called in the interrupt context. If watchdog pretimeout
+governor framework (kbuild CONFIG_WATCHDOG_PRETIMEOUT_GOV symbol) is enabled,
+an action is taken by a preconfigured pretimeout governor preassigned to
+the watchdog device. If watchdog pretimeout governor framework is not
+enabled, watchdog_notify_pretimeout() prints a notification message to
+the kernel log buffer.
+
+To set the last known HW keepalive time for a watchdog, the following function
+should be used::
+
+  int watchdog_set_last_hw_keepalive(struct watchdog_device *wdd,
+                                     unsigned int last_ping_ms)
+
+This function must be called immediately after watchdog registration. It
+sets the last known hardware heartbeat to have happened last_ping_ms before
+current time. Calling this is only needed if the watchdog is already running
+when probe is called, and the watchdog can only be pinged after the
+min_hw_heartbeat_ms time has passed from the last ping.
diff --git a/Documentation/watchdog/watchdog-parameters.rst b/Documentation/watchdog/watchdog-parameters.rst
new file mode 100644
index 000000000..223c99361
--- /dev/null
+++ b/Documentation/watchdog/watchdog-parameters.rst
@@ -0,0 +1,728 @@
+==========================
+WatchDog Module Parameters
+==========================
+
+This file provides information on the module parameters of many of
+the Linux watchdog drivers.  Watchdog driver parameter specs should
+be listed here unless the driver has its own driver-specific information
+file.
+
+See Documentation/admin-guide/kernel-parameters.rst for information on
+providing kernel parameters for builtin drivers versus loadable
+modules.
+
+-------------------------------------------------
+
+watchdog core:
+    open_timeout:
+	Maximum time, in seconds, for which the watchdog framework will take
+	care of pinging a running hardware watchdog until userspace opens the
+	corresponding /dev/watchdogN device. A value of 0 means an infinite
+	timeout. Setting this to a non-zero value can be useful to ensure that
+	either userspace comes up properly, or the board gets reset and allows
+	fallback logic in the bootloader to try something else.
+
+-------------------------------------------------
+
+acquirewdt:
+    wdt_stop:
+	Acquire WDT 'stop' io port (default 0x43)
+    wdt_start:
+	Acquire WDT 'start' io port (default 0x443)
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+advantechwdt:
+    wdt_stop:
+	Advantech WDT 'stop' io port (default 0x443)
+    wdt_start:
+	Advantech WDT 'start' io port (default 0x443)
+    timeout:
+	Watchdog timeout in seconds. 1<= timeout <=63, default=60.
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+alim1535_wdt:
+    timeout:
+	Watchdog timeout in seconds. (0 < timeout < 18000, default=60
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+alim7101_wdt:
+    timeout:
+	Watchdog timeout in seconds. (1<=timeout<=3600, default=30
+    use_gpio:
+	Use the gpio watchdog (required by old cobalt boards).
+	default=0/off/no
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+ar7_wdt:
+    margin:
+	Watchdog margin in seconds (default=60)
+    nowayout:
+	Disable watchdog shutdown on close
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+armada_37xx_wdt:
+    timeout:
+	Watchdog timeout in seconds. (default=120)
+    nowayout:
+	Disable watchdog shutdown on close
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+at91rm9200_wdt:
+    wdt_time:
+	Watchdog time in seconds. (default=5)
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+at91sam9_wdt:
+    heartbeat:
+	Watchdog heartbeats in seconds. (default = 15)
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+bcm47xx_wdt:
+    wdt_time:
+	Watchdog time in seconds. (default=30)
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+coh901327_wdt:
+    margin:
+	Watchdog margin in seconds (default 60s)
+
+-------------------------------------------------
+
+cpu5wdt:
+    port:
+	base address of watchdog card, default is 0x91
+    verbose:
+	be verbose, default is 0 (no)
+    ticks:
+	count down ticks, default is 10000
+
+-------------------------------------------------
+
+cpwd:
+    wd0_timeout:
+	Default watchdog0 timeout in 1/10secs
+    wd1_timeout:
+	Default watchdog1 timeout in 1/10secs
+    wd2_timeout:
+	Default watchdog2 timeout in 1/10secs
+
+-------------------------------------------------
+
+da9052wdt:
+    timeout:
+	Watchdog timeout in seconds. 2<= timeout <=131, default=2.048s
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+davinci_wdt:
+    heartbeat:
+	Watchdog heartbeat period in seconds from 1 to 600, default 60
+
+-------------------------------------------------
+
+ebc-c384_wdt:
+    timeout:
+	Watchdog timeout in seconds. (1<=timeout<=15300, default=60)
+    nowayout:
+	Watchdog cannot be stopped once started
+
+-------------------------------------------------
+
+ep93xx_wdt:
+    nowayout:
+	Watchdog cannot be stopped once started
+    timeout:
+	Watchdog timeout in seconds. (1<=timeout<=3600, default=TBD)
+
+-------------------------------------------------
+
+eurotechwdt:
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+    io:
+	Eurotech WDT io port (default=0x3f0)
+    irq:
+	Eurotech WDT irq (default=10)
+    ev:
+	Eurotech WDT event type (default is `int`)
+
+-------------------------------------------------
+
+gef_wdt:
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+geodewdt:
+    timeout:
+	Watchdog timeout in seconds. 1<= timeout <=131, default=60.
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+i6300esb:
+    heartbeat:
+	Watchdog heartbeat in seconds. (1<heartbeat<2046, default=30)
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+iTCO_wdt:
+    heartbeat:
+	Watchdog heartbeat in seconds.
+	(2<heartbeat<39 (TCO v1) or 613 (TCO v2), default=30)
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+iTCO_vendor_support:
+    vendorsupport:
+	iTCO vendor specific support mode, default=0 (none),
+	1=SuperMicro Pent3, 2=SuperMicro Pent4+, 911=Broken SMI BIOS
+
+-------------------------------------------------
+
+ib700wdt:
+    timeout:
+	Watchdog timeout in seconds. 0<= timeout <=30, default=30.
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+ibmasr:
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+imx2_wdt:
+    timeout:
+	Watchdog timeout in seconds (default 60 s)
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+indydog:
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+iop_wdt:
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+it8712f_wdt:
+    margin:
+	Watchdog margin in seconds (default 60)
+    nowayout:
+	Disable watchdog shutdown on close
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+it87_wdt:
+    nogameport:
+	Forbid the activation of game port, default=0
+    nocir:
+	Forbid the use of CIR (workaround for some buggy setups); set to 1 if
+system resets despite watchdog daemon running, default=0
+    exclusive:
+	Watchdog exclusive device open, default=1
+    timeout:
+	Watchdog timeout in seconds, default=60
+    testmode:
+	Watchdog test mode (1 = no reboot), default=0
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+ixp4xx_wdt:
+    heartbeat:
+	Watchdog heartbeat in seconds (default 60s)
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+machzwd:
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+    action:
+	after watchdog resets, generate:
+	0 = RESET(*)  1 = SMI  2 = NMI  3 = SCI
+
+-------------------------------------------------
+
+max63xx_wdt:
+    heartbeat:
+	Watchdog heartbeat period in seconds from 1 to 60, default 60
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+    nodelay:
+	Force selection of a timeout setting without initial delay
+	(max6373/74 only, default=0)
+
+-------------------------------------------------
+
+mixcomwd:
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+mpc8xxx_wdt:
+    timeout:
+	Watchdog timeout in ticks. (0<timeout<65536, default=65535)
+    reset:
+	Watchdog Interrupt/Reset Mode. 0 = interrupt, 1 = reset
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+mv64x60_wdt:
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+ni903x_wdt:
+    timeout:
+	Initial watchdog timeout in seconds (0<timeout<516, default=60)
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+nic7018_wdt:
+    timeout:
+	Initial watchdog timeout in seconds (0<timeout<464, default=80)
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+omap_wdt:
+    timer_margin:
+	initial watchdog timeout (in seconds)
+    early_enable:
+	Watchdog is started on module insertion (default=0
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+orion_wdt:
+    heartbeat:
+	Initial watchdog heartbeat in seconds
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+pc87413_wdt:
+    io:
+	pc87413 WDT I/O port (default: io).
+    timeout:
+	Watchdog timeout in minutes (default=timeout).
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+pika_wdt:
+    heartbeat:
+	Watchdog heartbeats in seconds. (default = 15)
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+pnx4008_wdt:
+    heartbeat:
+	Watchdog heartbeat period in seconds from 1 to 60, default 19
+    nowayout:
+	Set to 1 to keep watchdog running after device release
+
+-------------------------------------------------
+
+pnx833x_wdt:
+    timeout:
+	Watchdog timeout in Mhz. (68Mhz clock), default=2040000000 (30 seconds)
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+    start_enabled:
+	Watchdog is started on module insertion (default=1)
+
+-------------------------------------------------
+
+rc32434_wdt:
+    timeout:
+	Watchdog timeout value, in seconds (default=20)
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+riowd:
+    riowd_timeout:
+	Watchdog timeout in minutes (default=1)
+
+-------------------------------------------------
+
+s3c2410_wdt:
+    tmr_margin:
+	Watchdog tmr_margin in seconds. (default=15)
+    tmr_atboot:
+	Watchdog is started at boot time if set to 1, default=0
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+    soft_noboot:
+	Watchdog action, set to 1 to ignore reboots, 0 to reboot
+    debug:
+	Watchdog debug, set to >1 for debug, (default 0)
+
+-------------------------------------------------
+
+sa1100_wdt:
+    margin:
+	Watchdog margin in seconds (default 60s)
+
+-------------------------------------------------
+
+sb_wdog:
+    timeout:
+	Watchdog timeout in microseconds (max/default 8388607 or 8.3ish secs)
+
+-------------------------------------------------
+
+sbc60xxwdt:
+    wdt_stop:
+	SBC60xx WDT 'stop' io port (default 0x45)
+    wdt_start:
+	SBC60xx WDT 'start' io port (default 0x443)
+    timeout:
+	Watchdog timeout in seconds. (1<=timeout<=3600, default=30)
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+sbc7240_wdt:
+    timeout:
+	Watchdog timeout in seconds. (1<=timeout<=255, default=30)
+    nowayout:
+	Disable watchdog when closing device file
+
+-------------------------------------------------
+
+sbc8360:
+    timeout:
+	Index into timeout table (0-63) (default=27 (60s))
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+sbc_epx_c3:
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+sbc_fitpc2_wdt:
+    margin:
+	Watchdog margin in seconds (default 60s)
+    nowayout:
+	Watchdog cannot be stopped once started
+
+-------------------------------------------------
+
+sbsa_gwdt:
+    timeout:
+	Watchdog timeout in seconds. (default 10s)
+    action:
+	Watchdog action at the first stage timeout,
+	set to 0 to ignore, 1 to panic. (default=0)
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+sc1200wdt:
+    isapnp:
+	When set to 0 driver ISA PnP support will be disabled (default=1)
+    io:
+	io port
+    timeout:
+	range is 0-255 minutes, default is 1
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+sc520_wdt:
+    timeout:
+	Watchdog timeout in seconds. (1 <= timeout <= 3600, default=30)
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+sch311x_wdt:
+    force_id:
+	Override the detected device ID
+    therm_trip:
+	Should a ThermTrip trigger the reset generator
+    timeout:
+	Watchdog timeout in seconds. 1<= timeout <=15300, default=60
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+scx200_wdt:
+    margin:
+	Watchdog margin in seconds
+    nowayout:
+	Disable watchdog shutdown on close
+
+-------------------------------------------------
+
+shwdt:
+    clock_division_ratio:
+	Clock division ratio. Valid ranges are from 0x5 (1.31ms)
+	to 0x7 (5.25ms). (default=7)
+    heartbeat:
+	Watchdog heartbeat in seconds. (1 <= heartbeat <= 3600, default=30
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+smsc37b787_wdt:
+    timeout:
+	range is 1-255 units, default is 60
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+softdog:
+    soft_margin:
+	Watchdog soft_margin in seconds.
+	(0 < soft_margin < 65536, default=60)
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+    soft_noboot:
+	Softdog action, set to 1 to ignore reboots, 0 to reboot
+	(default=0)
+
+-------------------------------------------------
+
+stmp3xxx_wdt:
+    heartbeat:
+	Watchdog heartbeat period in seconds from 1 to 4194304, default 19
+
+-------------------------------------------------
+
+tegra_wdt:
+    heartbeat:
+	Watchdog heartbeats in seconds. (default = 120)
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+ts72xx_wdt:
+    timeout:
+	Watchdog timeout in seconds. (1 <= timeout <= 8, default=8)
+    nowayout:
+	Disable watchdog shutdown on close
+
+-------------------------------------------------
+
+twl4030_wdt:
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+txx9wdt:
+    timeout:
+	Watchdog timeout in seconds. (0<timeout<N, default=60)
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+uniphier_wdt:
+    timeout:
+	Watchdog timeout in power of two seconds.
+	(1 <= timeout <= 128, default=64)
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+w83627hf_wdt:
+    wdt_io:
+	w83627hf/thf WDT io port (default 0x2E)
+    timeout:
+	Watchdog timeout in seconds. 1 <= timeout <= 255, default=60.
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+w83877f_wdt:
+    timeout:
+	Watchdog timeout in seconds. (1<=timeout<=3600, default=30)
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+w83977f_wdt:
+    timeout:
+	Watchdog timeout in seconds (15..7635), default=45)
+    testmode:
+	Watchdog testmode (1 = no reboot), default=0
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+wafer5823wdt:
+    timeout:
+	Watchdog timeout in seconds. 1 <= timeout <= 255, default=60.
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+wdt285:
+    soft_margin:
+	Watchdog timeout in seconds (default=60)
+
+-------------------------------------------------
+
+wdt977:
+    timeout:
+	Watchdog timeout in seconds (60..15300, default=60)
+    testmode:
+	Watchdog testmode (1 = no reboot), default=0
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+wm831x_wdt:
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+wm8350_wdt:
+    nowayout:
+	Watchdog cannot be stopped once started
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
+sun4v_wdt:
+    timeout_ms:
+	Watchdog timeout in milliseconds 1..180000, default=60000)
+    nowayout:
+	Watchdog cannot be stopped once started
diff --git a/Documentation/watchdog/watchdog-pm.rst b/Documentation/watchdog/watchdog-pm.rst
new file mode 100644
index 000000000..646e1f28f
--- /dev/null
+++ b/Documentation/watchdog/watchdog-pm.rst
@@ -0,0 +1,22 @@
+===============================================
+The Linux WatchDog Timer Power Management Guide
+===============================================
+
+Last reviewed: 17-Dec-2018
+
+Wolfram Sang <wsa+renesas@sang-engineering.com>
+
+Introduction
+------------
+This document states rules about watchdog devices and their power management
+handling to ensure a uniform behaviour for Linux systems.
+
+
+Ping on resume
+--------------
+On resume, a watchdog timer shall be reset to its selected value to give
+userspace enough time to resume. [1] [2]
+
+[1] https://patchwork.kernel.org/patch/10252209/
+
+[2] https://patchwork.kernel.org/patch/10711625/
diff --git a/Documentation/watchdog/wdt.rst b/Documentation/watchdog/wdt.rst
new file mode 100644
index 000000000..d97b03615
--- /dev/null
+++ b/Documentation/watchdog/wdt.rst
@@ -0,0 +1,63 @@
+============================================================
+WDT Watchdog Timer Interfaces For The Linux Operating System
+============================================================
+
+Last Reviewed: 10/05/2007
+
+Alan Cox <alan@lxorguk.ukuu.org.uk>
+
+	- ICS	WDT501-P
+	- ICS	WDT501-P (no fan tachometer)
+	- ICS	WDT500-P
+
+All the interfaces provide /dev/watchdog, which when open must be written
+to within a timeout or the machine will reboot. Each write delays the reboot
+time another timeout. In the case of the software watchdog the ability to
+reboot will depend on the state of the machines and interrupts. The hardware
+boards physically pull the machine down off their own onboard timers and
+will reboot from almost anything.
+
+A second temperature monitoring interface is available on the WDT501P cards.
+This provides /dev/temperature. This is the machine internal temperature in
+degrees Fahrenheit. Each read returns a single byte giving the temperature.
+
+The third interface logs kernel messages on additional alert events.
+
+The ICS ISA-bus wdt card cannot be safely probed for. Instead you need to
+pass IO address and IRQ boot parameters.  E.g.::
+
+	wdt.io=0x240 wdt.irq=11
+
+Other "wdt" driver parameters are:
+
+	===========	======================================================
+	heartbeat	Watchdog heartbeat in seconds (default 60)
+	nowayout	Watchdog cannot be stopped once started (kernel
+			build parameter)
+	tachometer	WDT501-P Fan Tachometer support (0=disable, default=0)
+	type		WDT501-P Card type (500 or 501, default=500)
+	===========	======================================================
+
+Features
+--------
+
+================   =======	   =======
+		   WDT501P	   WDT500P
+================   =======	   =======
+Reboot Timer	   X               X
+External Reboot	   X	           X
+I/O Port Monitor   o		   o
+Temperature	   X		   o
+Fan Speed          X		   o
+Power Under	   X               o
+Power Over         X               o
+Overheat           X               o
+================   =======	   =======
+
+The external event interfaces on the WDT boards are not currently supported.
+Minor numbers are however allocated for it.
+
+
+Example Watchdog Driver:
+
+	see samples/watchdog/watchdog-simple.c