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authorMichael Shych <michaelsh@mellanox.com>2019-02-24 17:26:31 +0000
committerWim Van Sebroeck <wim@linux-watchdog.org>2019-03-02 15:28:20 +0100
commit9d489ad121927609d6e51df1a755707966945a53 (patch)
tree3dabcc902f5ecebe64a70c37ee162f7e9b0b22e9 /Documentation/watchdog
parentc60923dd5feedc337b1450e3f4c6e19ffa305439 (diff)
downloadlinux-9d489ad121927609d6e51df1a755707966945a53.tar.bz2
Documentation/watchdog: Add documentation mlx-wdt driver
Add documentation with details of Mellanox watchdog driver. Signed-off-by: Michael Shych <michaelsh@mellanox.com> Reviewed-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>
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+ 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 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.
+
+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.