Re: [Phishing Risk] [External] Re: Does it make sense to create a centralized fan control module?

From: John Wang <wangzhiqiang.bj@bytedance.com>
To: Heyi Guo <guoheyi@linux.alibaba.com>
Cc: Zhikui Ren <zhikui.ren@intel.com>,
	Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>,
	Vernon Mauery <vernon.mauery@linux.intel.com>,
	OpenBMC Maillist <openbmc@lists.ozlabs.org>,
	Ed Tanous <ed@tanous.net>, Josh Lehan <krellan@google.com>,
	Ed Tanous <edtanous@google.com>,
	Patrick Venture <venture@google.com>
Subject: Re: [Phishing Risk] [External] Re: Does it make sense to create a centralized fan control module?
Date: Wed, 16 Jun 2021 10:49:36 +0800	[thread overview]
Message-ID: <CAH0XSJupSg54T_6qpPPHHBjHcR5OFZ3+VcaGEaP+PR+6F5ny1g@mail.gmail.com> (raw)
In-Reply-To: <71dfdfc0-1eff-efb6-094c-de71f6f8cc87@linux.alibaba.com>

On Wed, Jun 16, 2021 at 10:02 AM Heyi Guo <guoheyi@linux.alibaba.com> wrote:
>
> Hi All,
>
> Any comments for my questions at the top of this thread?
>
> Thanks,
>
> Heyi
>
>
> On 2021/6/11 上午9:23, Heyi Guo wrote:
> > Please ignore my early emails; only this one is the final version. I
> > must have misused some shortcut key to send the unfinished versions
> > while I wanted to save it locally...
> >
> > Sorry for the noise.
> >
> > Heyi
> >
> > On 2021/6/11 上午9:14, Heyi Guo wrote:
> >> Hi All,
> >>
> >> Right now fan related data like tacho and PWM is fetched in
> >> dbus-sensors, and published to d-bus as sensor data, while fan
> >> control is made in another module like pid-control, which can fetch
> >> data and set value via d-bus.
> >>
> >> In some common sense, we may think about putting all fan related work
> >> into one single module (which may be based on pid-control), i.e. it
> >> can read tacho and PWM from hardware directly, calculate the required

As I understand it, if you just want to bypass dbus and read pwm/tach
directly you can refer to this.
https://github.com/openbmc/openbmc/blob/master/meta-quanta/meta-gsj/recipes-phosphor/fans/phosphor-pid-control/config-2ssd.json#L6-L7

> >> PWM by some algorithm like PID, and then write to PWM hardware
> >> directly; the data will also be published to d-bus for other modules
> >> to consume, like fansensor from dbus-sensors.
> >>
> >> Does it make sense to do that? Or is there any reason for the current
> >> design?

I don't know why it's designed this way, but are you experiencing any problems?
According to our past experience, pid-control reads/writes pwm/tach
quite smoothly,
but pid-control has some trouble reading the temperature of some
sensors via dbus.(eg psusensors).
That's another topic...

> >>
> >> I'm new to OpenBMC and some of my understanding may be totally wrong.
> >>
> >> Looking forward to your expert advice.
> >>
> >> Thanks,
> >>
> >> Heyi