Plans regarding PECI sensors and PCIe inventory with upstream Linux

[Paul Fertser]

Hello Iwona,

On Fri, Mar 24, 2023 at 09:38:04PM +0000, Winiarska, Iwona wrote:
> On Wed, 2023-03-22 at 16:14 +0300, Paul Fertser wrote:
> > Recently OpenBMC switched to newer Linux version which got upstream
> > support for the PECI bus, with CPU and DIMM modules temperature
> > sensors reported via it. I assume this is essential for all
> > Intel-based server motherboards as monitoring CPU temperature and
> > spinning fans accordingly is one of the core BMC functionalities.
> 
> Yes, it's currently not compatible with upstream PECI.
> 
> In January there was a thread related to dbus-sensors present and future:
> https://lore.kernel.org/openbmc/Y79U52toP0+Y4edh@hatter.bewilderbeest.net/
> where Zev mentioned that he started to work on dbus-sensors replacement, which
> does support (among other things) upstream PECI:
> 
> https://github.com/zevweiss/omnisensor/blob/master/src/peci.rs

It's a rather cool project, but I do not see it having become part of
OpenBMC mainstream just yet. Probably not many have tried even just
testing it, as I only see commits from Zev himself. I hope this will
change in the future.

For now I figured a simple change seems to be enough to allow
IntelCPUSensor from dbus-sensors to continue working on current
OpenBMC:

https://gerrit.openbmc.org/c/openbmc/dbus-sensors/+/62025

> Regarding peci-pcie, the plan would be to, instead of using pecidev, implement a
> PECI driver on the kernel side, which exposes the necessary information over
> sysfs (abstracting away the PECI commands used internally) and use that in peci-
> pcie.

When I was asking about plans I meant something with specific dates,
not just the general outline :) You can see as it currently stands
OpenBMC upstream lost the very essential feature (fan control
depending on CPU temperature) for most (all?) Intel-based servers, so
I'm surprised there's no particular migration path ready in
advance.

That said, thank you for the upstreaming work, I see it was attempted
before for years and you're the one who finally managed to do the
right (from Linux maintainers PoV) thing. Congratulations!

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