Feature request in phosphor-pid-control

[Tanous, Ed]

We've had a few discussions about this in previous code reviews.  I think the conclusion was that we need to add a "status" field/interface to sensors, so we can report OK/Unavailable/Error statuses outside of the existing value interface.  So far as I know, no one has proposed one of these yet, but I would happily help review a patch.

Also, (not Patrick) I would support a parameter in phosphor-pid-control that makes sensors optional.  The only part that worries me here is that there is a big difference at a system level between "unavailable" and "faulted", but I think that could be easily fixed in a future patchset if we get the full DBus support for status interfaces.

-Ed





From: openbmc [mailto:openbmc-bounces+ed.tanous=intel.com at lists.ozlabs.org] On Behalf Of Lei YU
Sent: Thursday, June 14, 2018 12:24 AM
To: OpenBMC Maillist <openbmc at lists.ozlabs.org>; Patrick Venture <venture at google.com>
Subject: Feature request in phosphor-pid-control

This email is about a feature request in phosphor-pid-control, that to support
optional sensors.
It is mentioned in comment of https://gerrit.openbmc-project.xyz/#/c/11003/

Background:
Current phosphor-pid-control checks the temperature sensors and calculate the
expected fan speed.
It assumes the temperature sensors are always available. And if the sensor is
not there, the service throws exceptions.

The feature request:
I would like phosphor-pid-control to support "optional" sensors, that it may
be unavailable when system is running.
Such sensor is counted when it is available, and is ignored when it is
missing.

An use case:
I want to adjust fan speed based on cpu core or dimm temperature.
For a typical OpenPOWER P9 system, there could be at most 48 cores, but they
can be missing depending on the CPU, e.g. if a system is plugged CPUs with 22
cores, 4 cores temperature will be missing. And in run time, a core may be
garded if it has problem it will be missing as well.
The same for dimms, for a system with at most 16 dimms, it depends on how many
dimms are attached.
In such case, the config will specify all the temperatures for cpu cores and
dimms, and phosphor-pid-control shall ignore the missing temperatures.

Patrick, what do you think about such case?

Thanks!