Re: [PATCH v1 3/6] clocksource/drivers/exynos_mct: Set local timer interrupts as percpu

[Youngmin Nam]

On Tue, Apr 01, 2025 at 09:36:19AM -0700, William McVicker wrote:
> On 03/31/2025, John Stultz wrote:
> > On Mon, Mar 31, 2025 at 4:00 PM 'Will McVicker' via kernel-team
> > <kernel-team@xxxxxxxxxxx> wrote:
> > >
> > > From: Hosung Kim <hosung0.kim@xxxxxxxxxxx>
> > >
> > > The MCT local timers can be used as a per-cpu event timer. To prevent
> > 
> > Can be used, or are used?  If it's an option, is this change important
> > in both cases?
> > 
> > > the timer interrupts from migrating to other CPUs, set the flag
> > > IRQF_PERCPU.
> > 
> > Might be work expanding this a bit to clarify why the interrupts
> > migrating to other cpus is undesired.
> 
> Let me dig into this further to figure out if the IP has a limitation where the
> interrupts need to be handled by the CPU the timer was triggered on or if this
> is just an optimization.
> 
> Any chance you know this @Youngmin?
> 
> Thanks,
> Will
> 

Hi Will.

Yes. In downstream, we’ve been using MCT as the clock event timer instead of the ARM timer.
Setting this flag allows each CPU to handle its own clock events, such as scheduling interrupts.

> > 
> > > Signed-off-by: Hosung Kim <hosung0.kim@xxxxxxxxxxx>
> > > [Original commit from https://android.googlesource.com/kernel/gs/+/03267fad19f093bac979ca78309483e9eb3a8d16]
> > > Signed-off-by: Will McVicker <willmcvicker@xxxxxxxxxx>
> > 
> > thanks!
> > -john
> 
>