[Feature] add GA346 baseline version
Change-Id: Ic62933698569507dcf98240cdf5d9931ae34348f
diff --git a/src/kernel/linux/v4.19/Documentation/watchdog/watchdog-kernel-api.txt b/src/kernel/linux/v4.19/Documentation/watchdog/watchdog-kernel-api.txt
new file mode 100644
index 0000000..9b93953
--- /dev/null
+++ b/src/kernel/linux/v4.19/Documentation/watchdog/watchdog-kernel-api.txt
@@ -0,0 +1,309 @@
+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.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 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 *);
+ 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);
+ int (*set_pretimeout)(struct watchdog_device *, unsigned int);
+ unsigned int (*get_timeleft)(struct watchdog_device *);
+ int (*restart)(struct watchdog_device *);
+ void (*ref)(struct watchdog_device *) __deprecated;
+ void (*unref)(struct watchdog_device *) __deprecated;
+ 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 'ref' and 'unref' operations are no longer used and deprecated.
+
+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.