Plans regarding PECI sensors and PCIe inventory with upstream Linux

[Winiarska, Iwona]

On Wed, 2023-03-22 at 16:14 +0300, Paul Fertser wrote:
> Hello,
> 
> 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.
> 
> However, I wasn't able to find[0] any sign that this code can actually
> be used in OpenBMC. intelcpusensor daemon exits early as the upstream
> code doesn't implement the IOCTLs for direct userspace bus
> operations. Is there any work planned to make it compatible, or was
> some other way chosen?

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

> 
> Another related question is that peci-pcie daemon used for enumerating
> host PCIe devices can no longer be used due to the same reason, is
> there some replacement in the works? Where can I track its
> development?

When it comes to pecidev, I didn't plan to have it available upstream.
From my perspective - the uAPI exposed by pecidev is too low-level to be used
for anything other than development purpose. It would also be very tricky to
support certain PECI features reliably (such as wake on peci) in the future if
pecidev was available.

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.

Thanks
-Iwona

> 
> [0]
> https://gerrit.openbmc.org/q/project:openbmc/dbus-sensors+message:intelcpusensor
>