Le 09/04/2021 à 16:12, Rasmus Villemoes a écrit :
On powerpc, time as measured by get_timer() ceases to pass when interrupts are disabled (since on powerpc get_timer() returns the value of a volatile variable that gets updated via a timer interrupt). That in turn means the watchdog_reset() function provided by CONFIG_WDT ceases to work due to the ratelimiting it imposes.
Normally, interrupts are just disabled very briefly. However, during bootm, they are disabled for good prior to decompressing the kernel image, which can be a somewhat time-consuming operation. Even when we manage to decompress the kernel and do the other preparation steps and hand over control to the kernel, the kernel also takes some time before it is ready to assume responsibility for handling the watchdog. The end result is that the board gets reset prematurely.
The ratelimiting isn't really strictly needed (prior to DM WDT, no such thing existed), so just disable it when we know that time no longer passes and have watchdog_reset() (e.g. called from decompression loop) unconditionally reset the watchdog timer.
Do we need to make it that complicated ? I think before the generic implementation, powerpc didn't have a rate limitation at all for pinging the watchdog, why not go back this direction, all the time ?
I mean we could simply set reset_period to 0 at all time for powerpc ( and change the test to time_after_eq() instead of time_after() ).
Signed-off-by: Rasmus Villemoes rasmus.villemoes@prevas.dk
I previously sent a patch to change the ratelimiting to be based on get_ticks() instead of get_timer(), but that has gone nowhere [1]. This is an alternative which only affects powerpc (and only boards that have enabled CONFIG_WDT). I hope the watchdog maintainers will accept at least one of these, or suggest a third alternative, so I don't have to keep some out-of-tree patch applied without knowing if that's the direction upstream will take.
[1] https://patchwork.ozlabs.org/project/uboot/patch/20200605111657.28773-1-rasm...