Re: [PATCH 2/3] arm64: smp: Implement cpus_has_pending_ipi()

Sudeep Holla
2025-10-06T14:41:45Z

On Mon, Oct 06, 2025 at 02:22:49PM +0200, Ulf Hansson wrote:
> On Mon, 6 Oct 2025 at 12:54, Sudeep Holla <sudeep.holla@arm.com> wrote:
> >
> > 2. I understand this is intended for the DragonBoard 410c, where the firmware
> > can’t be updated. However, ideally, the PSCI firmware should handle checking
> > for pending IPIs if that’s important for the platform. The firmware could
> > perform this check at the CPU PPU/HW level and prevent entering the
> > state if needed.
>
> I think this is exactly what is happening on Dragonboard 410c (see the
> stats I shared in the commit message in patch3).
>
> The PSCI FW refuses to enter the suggested idlestate and the call fails.
>

Ah OK, the PSCI FW is doing the job correctly, we are just attempting to
reduce the failures by catching few cases earlier in the OSPM itself ?
Sure it only reduces the failures but it can't eliminate those as IPI might
be issued after this check in the OSPM. I understand the call to firmware
can be prevented.

--
Regards,
Sudeep