Feedback on Current OpenBMC and Proposing Some Improvements ---- Difficulties and Issue Examples

[Alex Qiu]

Hi Patrick,

Thanks for the information! I'm taking a look at it...

- Alex Qiu

On Tue, Jun 23, 2020 at 6:20 PM Patrick Williams <patrick at stwcx.xyz> wrote:
>
> Hi Alex,
>
> On Tue, Jun 23, 2020 at 04:47:36PM -0700, Alex Qiu wrote:
> > For example, some of our FRU has way too many temperature sensors from
> > hardware design, but we only need the maximum temperature among these
> > sensors on one FRU to feed to the PID control loop or health
> > reporting. It would be great to aggregate the sensors according to
> > individual FRUs. You can see this sensor aggregation feature as a
> > simple example in my demo:
> > https://github.com/alex310110/bmc-proto-20q2/blob/master/downstream/card_example_g.py#L69
> >
> > We also encounter voltage regulator devices requiring current reading
> > corrections according to their own properties (duty cycle and
> > temperature). This correction is not preferred to perform within
> > kernel drivers, and we are suggested to deal with them in user space.
> > See "Read Output Current" in
> > https://www.maximintegrated.com/en/design/technical-documents/app-notes/6/6042.html
> > Example in demo:
> > https://github.com/alex310110/bmc-proto-20q2/blob/master/device_xam2734.py
> >
>
> We've been discussing a very similar feature to what you're describing
> here at Facebook.  There is a very rough design document at:
>
>     https://gerrit.openbmc-project.xyz/c/openbmc/docs/+/32345
>
> We need to have both aggregation sensors (the first) and corrections
> (the second).  The design document here allows both.
>
> On correction, my understanding is that we have some sensors that need
> an adjustment depending on a *different* sensor value.  For instance, a
> voltage regulator might have some error based on the ambient
> temperature.
>
> --
> Patrick Williams