[PATCH] watchdog: use time_after_eq() in watchdog_reset()

[Rasmus Villemoes]

On 15/04/2021 07.38, Stefan Roese wrote:
> On 13.04.21 16:43, Rasmus Villemoes wrote:
>> Some boards don't work with the rate-limiting done in the generic
>> watchdog_reset() provided by wdt-uclass.
>>
>> For example, on powerpc, get_timer() ceases working during bootm since
>> interrupts are disabled before the kernel image gets decompressed, and
>> when the decompression takes longer than the watchdog device
>> allows (or enough of the budget that the kernel doesn't get far enough
>> to assume responsibility for petting the watchdog), the result is a
>> non-booting board.
>>
>> As a somewhat hacky workaround (because DT is supposed to describe
>> hardware), allow specifying hw_margin_ms=0 in device tree to
>> effectively disable the ratelimiting and actually ping the watchdog
>> every time watchdog_reset() is called. For that to work, the "has
>> enough time passed" check just needs to be tweaked a little to allow
>> the now==next_reset case as well.
>>
>> Suggested-by: Christophe Leroy <christophe.leroy at csgroup.eu>
>> Signed-off-by: Rasmus Villemoes <rasmus.villemoes at prevas.dk>
>> ---
>>
>> It's the option I dislike the most (because of the DT abuse), but I
>> also do accept that it's the one with the minimal code impact, and
>> apparently the path of least resistance. So here it is.
> 
> Right. An alternative way would have been to add a new Kconfig symbol
> to define the default value of "reset_period" so that it can be
> configured to different values via Kconfig as well.

No, I don't think we should not go in that direction.

Another thing I have on my todo-list is to rewrite the watchdog_reset()
in wdt-uclass to handle _all_ DM watchdogs, not just the first one. Some
boards make use of both the one in the CPU/SOC as well as some
gpio-triggered one. Both the hw_margin_ms/reset_period and the
last_reset data would then have to live with the device, not be static
variables. Last I looked, it does seem that the DM code supports having
a piece of class-owned, per-device data, so it shouldn't be too hard to do.

Rasmus