[PATCH 0/3] watchdog: honour hw_margin_ms property

[Rasmus Villemoes]

On 16/03/2020 16.52, Rasmus Villemoes wrote:
> On 14/03/2020 13.04, Stefan Roese wrote:
>> On 13.03.20 17:04, Rasmus Villemoes wrote:
> 
>>> That at least solves half my problems and
>>> might be useful to others as well. Then I'll have to figure out the
>>> time-stands-still problem in some other way.
>>
>> If its too hard to enable interrupts in SPL for you or to provide some
>> other means of a working get_timer() API, then we needto find another
>> solution. You started with this weak function, which of course works.
>> What other options are there? Adding a callback mechanism to register
>> platform specific callback functions? Even though this might get a
>> little bit too complicated.
> 
> Now that I dig a bit more into this, I seem to remember that we actually
> also had problems in U-Boot proper when loading a compressed kernel, so
> for now we're using an uncompressed kernel in our FIT images. I will
> have to re-investigate, but it now occurs to me that it might be due to
> the fact that interrupts get disabled during bootm (which makes sense,
> the same reason I stated previously of interrupt vectors about to be
> overwritten), so even in U-Boot proper, time as measured by get_timer()
> ceases to pass after that point, so all the WATCHDOG_RESET() calls from
> the inflate code effectively get ignored.
> 
> So it may be necessary to have some wdt_ratelimit_disable() hook that
> can be called from bootm_disable_interrupts() and e.g. some
> board-specific SPL code. I'll do some experiments and figure out if I do
> indeed need such a hook.

OK, I have now had time to do some more experiments. I have enabled the
timer tick in SPL, so get_timer() now "normally" works. Together with
the .dts based read of the hardware margin, that makes the watchdog
handling mostly work.

But, as I suspected, I do have a problem when loading a compressed
kernel image - what I write above "so even in U-Boot proper, time as
measured by get_timer() ceases to pass after that point, so all the
WATCHDOG_RESET() calls from the inflate code effectively get ignored."
is indeed the case.

So, what's the best way to proceed? Should there be a hook disabling the
 rate-limiting logic that bootm_disable_interrupts() can call? Or must
get_timer() always return a sensible result even with interrupts disabled?

Rasmus