Re: [PATCH v5 1/1] Documentation/watchdog: Add documentation mlx-wdt driver

[Guenter Roeck <linux@roeck-us.net>]

On 2/24/19 9:26 AM, michaelsh@mellanox.com wrote:
> From: Michael Shych <michaelsh@mellanox.com>
> 
> Add documentation with details of Mellanox watchdog driver.
> 
> Signed-off-by: Michael Shych <michaelsh@mellanox.com>

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

> ---
> v1->v4
> 1. Remove sentence that now doesn't correspond to code.
> 2. Add explanations about nowayout and start_at_boot options.
> ---
> v5->v4
> Fix typo in nowayout explanation.
> ---
>   Documentation/watchdog/mlx-wdt.txt | 52 ++++++++++++++++++++++++++++++++++++++
>   1 file changed, 52 insertions(+)
>   create mode 100644 Documentation/watchdog/mlx-wdt.txt
> 
> diff --git a/Documentation/watchdog/mlx-wdt.txt b/Documentation/watchdog/mlx-wdt.txt
> new file mode 100644
> index 000000000000..66eeb78505c3
> --- /dev/null
> +++ b/Documentation/watchdog/mlx-wdt.txt
> @@ -0,0 +1,52 @@
> +		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.
>