Re: [PATCH v2 0/2] Update the watchdog period according to real CPU frequency

[Will Deacon <will@kernel.org>]

On Mon, May 12, 2025 at 04:06:12PM -0700, Andrew Morton wrote:
> On Mon, 12 May 2025 21:09:17 +0800 Yicong Yang <yangyicong@huawei.com> wrote:
> 
> > From: Yicong Yang <yangyicong@hisilicon.com>
> > 
> > watchdog perf needs architecture to provide method for converting the watchdog
> > thresh to counter period. For arm64 we're using the max CPU frequency for
> > doing the conversion which is from cpufreq driver. But some cpufreq driver
> > are registered lately, for example cppc_cpufreq will be registered at late
> > initcall which is after the initialization of watchdog perf (initialized in
> > armv8_pmuv3 of device initcall). In such case the period of watchdog will not
> > be accurate enough. Fix this by registering a cpufreq notifier and update the
> > watchdog period once the cpufreq driver is initialized.
> > 
> 
> Thanks.  Thoughts.
> 
> 1: What is the impact of this change?  Is the current code causing
>    problems?  If so, what are they?  How is the end-user experience
>    improved by this change?  Important info!
> 
> 2: As far as I can tell, this patchset impacts arm64 only.  Do you
>    think that other architectures should implement this?
> 
> 3: As far as I can tell, this patchset affects all cpufreq drivers
>    which use late_initcall() (on arm64, of course).  Is this correct?
> 
> 4: It is asserted that we should use the *maximum* possible CPU
>    frequency for this calculation.  Why?  I assume this is because we
>    care about the minimum watchdog period?
> 
> Can I assume that the ARM maintainers will be handling this?

Argh, this has all ended up in my spam for some reason...

Lemme go fish the patches back out. Andrew -- we can take these via
arm64 if you like (although I have some comments on the code first).

Will