Merge git://git.kernel.org/pub/scm/linux/kernel/git/wim/linux-watchdog

* Freescale i.MX Watchdog Timer (WDT) Controller

Required properties:

- compatible : Should be "fsl,<soc>-wdt"

- reg : Should contain WDT registers location and length

- interrupts : Should contain WDT interrupt

Examples:

wdt@73f98000 {

	compatible = "fsl,imx51-wdt", "fsl,imx21-wdt";

	reg = <0x73f98000 0x4000>;

	interrupts = <58>;

};

* Samsung's Watchdog Timer Controller

The Samsung's Watchdog controller is used for resuming system operation

after a preset amount of time during which the WDT reset event has not

occured.

Required properties:

- compatible : should be "samsung,s3c2410-wdt"

- reg : base physical address of the controller and length of memory mapped

	region.

- interrupts : interrupt number to the cpu.

	- directory holding watchdog related example programs.

watchdog-api.txt

	- description of the Linux Watchdog driver API.

watchdog-kernel-api.txt

	- description of the Linux WatchDog Timer Driver Core kernel API.

watchdog-parameters.txt

	- information on driver parameters (for drivers other than

	  the ones that have driver-specific files here)

The Linux WatchDog Timer Driver Core kernel API.

===============================================

Last reviewed: 22-Jul-2011

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.txt .

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 device structure looks like this:

struct watchdog_device {

	const struct watchdog_info *info;

	const struct watchdog_ops *ops;

	unsigned int bootstatus;

	unsigned int timeout;

	unsigned int min_timeout;

	unsigned int max_timeout;

	void *driver_data;

	unsigned long status;

};

It contains following fields:

* 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.

* timeout: the watchdog timer's timeout value (in seconds).

* min_timeout: the watchdog timer's minimum timeout value (in seconds).

* max_timeout: the watchdog timer's maximum timeout value (in seconds).

* 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_drvadata and

  watchdog_get_drvdata routines.

* 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, is the nowayout bit set, is the device opened via

  the /dev/watchdog interface or not, ...).

The list of watchdog operations is defined as:

struct watchdog_ops {

	struct module *owner;

	/* mandatory operations */

	int (*start)(struct watchdog_device *);

	int (*stop)(struct watchdog_device *);

	/* optional operations */

	int (*ping)(struct watchdog_device *);

	unsigned int (*status)(struct watchdog_device *);

	int (*set_timeout)(struct watchdog_device *, unsigned int);

	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.

* 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. The

  driver supporting this hardware needs to make sure that a start and stop

  routine is being provided. This can be done by using a timer in the driver

  that regularly sends a keepalive ping to the watchdog timer hardware.

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:

* 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.

* 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 the timeout

  value of the watchdog_device will be changed to the value that was just used

  to re-program the watchdog timer device.

  (Note: the WDIOF_SETTIMEOUT needs to be set in the options field of the

  watchdog's info structure).

* 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. When the watchdog is active after booting, then you should

  set this status bit (Note: when you register the watchdog timer device with

  this bit set, then opening /dev/watchdog will skip the start operation)

* WDOG_DEV_OPEN: this status bit shows whether or not the watchdog device

  was opened via /dev/watchdog.

  (This bit should only be used by the WatchDog Timer Driver Core).

* WDOG_ALLOW_RELEASE: this bit stores whether or not the magic close character

  has been sent (so that we can support the magic close feature).

  (This bit should only be used by the WatchDog Timer Driver Core).

* 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.

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 retruns the pointer to the driver specific data.

if WATCHDOG

config WATCHDOG_CORE

	bool "WatchDog Timer Driver Core"

	---help---

	  Say Y here if you want to use the new watchdog timer driver core.

	  This driver provides a framework for all watchdog timer drivers

	  and gives them the /dev/watchdog interface (and later also the

	  sysfs interface).

	  To compile this driver as a module, choose M here: the module will

	  be called watchdog.

config WATCHDOG_NOWAYOUT

	bool "Disable watchdog shutdown on close"

	help

	  To compile this driver as a module, choose M here: the

	  module will be called sa1100_wdt.

config DW_WATCHDOG

	tristate "Synopsys DesignWare watchdog"

	depends on ARM && HAVE_CLK

	help

	  Say Y here if to include support for the Synopsys DesignWare

	  watchdog timer found in many ARM chips.

	  To compile this driver as a module, choose M here: the

	  module will be called dw_wdt.

config MPCORE_WATCHDOG

	tristate "MPcore watchdog"

	depends on HAVE_ARM_TWD

config IMX2_WDT

	tristate "IMX2+ Watchdog"

	depends on ARCH_MX2 || ARCH_MX25 || ARCH_MX3 || ARCH_MX5

	depends on IMX_HAVE_PLATFORM_IMX2_WDT

	help

	  This is the driver for the hardware watchdog

	  on the Freescale IMX2 and later processors.

	  To compile this driver as a module, choose M here: the

	  module will be called m54xx_wdt.

# MicroBlaze Architecture

config XILINX_WATCHDOG

	tristate "Xilinx Watchdog timer"

	depends on MICROBLAZE

	---help---

	  Watchdog driver for the xps_timebase_wdt ip core.

	  IMPORTANT: The xps_timebase_wdt parent must have the property

	  "clock-frequency" at device tree.

	  To compile this driver as a module, choose M here: the

	  module will be called of_xilinx_wdt.

# MIPS Architecture

config ATH79_WDT