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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. |