Re: [PATCH 0/2] staging: nvec_power: quiesce EC queries for system suspend

[Gustavo Arantes]

Hello Marc,

thanks for reviewing.

On Sun, 15 Mar 2026, Marc Dietrich wrote:
> Reading out the battery info during boot takes some time as far as I
> remember, but I haven't tested your patches yet. Is the use of sync
> writes really required in order to realize a clean suspend?

You're right, I worked out some math on this, and I agree that the sync
conversion isn't strictly necessary.

The worst case with async writes during suspend is a reply arriving
after work has been cancelled. That reply would just be lost, and since
the poller refreshes everything on resume, there's no corruption or
crash â?? just one missed update.

The sync approach does avoid that window, but the cost is structural:
the battery metadata init serializes N queries, so the boot-time wall
time goes from roughly one EC round-trip to N * T_rt. With N = 3
(MANUFACTURER, MODEL, TYPE), the relative overhead is always 2x
regardless of how fast the EC is. Without hardware to measure T_rt
I can't tell whether that's 100ms or 2s of added latency, but either
way it's a cost with no real safety benefit.

> Are you able to test the change on real hardware?

Unfortunately I don't have access to Tegra 2 hardware, so this has
only been build-tested and reviewed by inspection. I'd appreciate it
if you or someone on the ac100 list could validate the v2 on a real
device.

If you think the lost-reply window during suspend is benign, I'd
prefer to drop patch 1 and send a v2 with just the PM hooks on top
of the existing async flow. Otherwise, I'm happy to keep the sync
conversion as-is.


Best regards,
Gustavo Arantes