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From: Patrick Venture <venture@google.com>
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Subject: Re: Queries in phosphor-pid-control(swampd)
To: Kumar Thangavel <thangavel.k@hcl.com>
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On Thu, Nov 5, 2020 at 4:22 AM Kumar Thangavel <thangavel.k@hcl.com> wrote:
>
> Classification: Internal
>
> Hi All,
>
>
>
>       Does the current phosphor-pid-control handled the fan failures or i=
f fan values is 0 ?  Looks like, it ignores the fan values is 0 case.
>
>       Could you please clarify me, how the fan(single/both) failures hand=
led. if both fan failures, Do we need to power off the chassis or need to d=
o power sled cycle ?

The answers to the failure behaviors you wish are outside the scope of
controlling the fans themselves.  As I understand it, it's up to you
or your use case what happens when fails start failing. The pid
control daemon has default fail-safe values you can set, as well as
minimum RPM set-points, so that if some things fail, it'll still move
forward operating in a best effort to cool the system.  But with fans
failing, if there's something more one wishes to do with it, my
recommendation would be to reach out with a broader email subject line
-- there may be something already in openbmc (probably is) that'll
track failures and trigger behaviors.

However, currently pid control doesn't "manage the system."  Which it
sounds like you want.  Or not?  Your question sounds like you're not
sure what the system _should_ do in a fan failure case, to which I
cannot reply.

Thanks!

>
>
>
> Thanks,
>
> Kumar.
>
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