[PATCH v2 0/2] Update the watchdog period according to real CPU frequency
Will Deacon
will at kernel.org
Fri Jun 27 08:26:15 PDT 2025
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 at huawei.com> wrote:
>
> > From: Yicong Yang <yangyicong at 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
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