[phosphor-pid-control] scaling issue

Kun Yi kunyi at google.com
Tue Sep 10 03:11:47 AEST 2019 

Sorry about the regression issue, Hank.
IIRC I proposed to have separate groups of min/max values in D-Bus and json
files since they convey different semantics.
At the end the min/max value was merged in the current way, because the
assumption that min/max values in json is only used for fan pwm and nothing
else -- which obviously is not true now.
Should we revisit the approach? Having something like 'fanPwmScale' as a
separate config param is a cleaner approach in my opinion.

On Mon, Sep 9, 2019 at 9:59 AM Patrick Venture <venture at google.com> wrote:

> On Thu, Sep 5, 2019 at 12:25 AM Hank Liou (劉晉翰) <Hank.Liou at quantatw.com>
> wrote:
> >
> > Hi Patrick,
> >
> >
> > Sorry for not clearly stating our problem. We have the following issue:
> >
> >
> > temp sensor gets 31(C) -> 31 / 0.255 = 121.57 -> pid uses 127.57 as
> input for temp sensor ->
> >
> > stepwise fan table output 100 duty -> full speed fan
>
> Ok, so you're getting a dbus-based min/max value and you want to
> ignore it?  In the json configuration, if you set the values to 0,
> they are set to the default (0), so there'd be no clean way to know to
> ignore dbus in this case, without adding a small check to only
> consider min/max from dbus when sensor is not temp/margin.  Basically,
> only care about min/max on dbus if type is "fan"
>
> If that's right, James do you have a cycle to look at this one-liner?
>
> >
> >
> > As a result, fan will be at full speed while temp is low. Before the
> commit fc2e803 [1], this won't happen. The root cause is that, before
> fc2e803, pid will use config min/max, which is 0 in our case. This would
> not trigger scaling function, namely scaleSensorReading, in util.cpp.
> However, after such commit, min/max would be non-zero (-128/127 from DBus).
> This will trigger scaling function.
> >
> >
> > [1]
> https://github.com/openbmc/phosphor-pid-control/commit/fc2e803f5d9256944e18c7c878a441606b1f121c
> >
> >
> > Hank
> >
> >
> > ________________________________
> > From: Hank Liou (劉晉翰)
> > Sent: Monday, September 2, 2019 4:52 PM
> > To: Patrick Venture
> > Cc: James Feist; openbmc at lists.ozlabs.org
> > Subject: Re: [phosphor-pid-control] scaling issue
> >
> >
> > Hi Patrick,
> >
> >
> > Since we use phosphor-sel-logger [1] at the same time, we do assign min
> and max of temp sensors to Dbus (max: 127, min: -128). So in the present
> case, our temp value will be divided by 0.255 (also due to exponent is -3
> here). This will cause re-scaling problem. Therefore there should be an
> statement to distinguish sensor types. If it is "temp", then one assigns 0
> to the min and max from Dbus.
> >
> >
> > [1]
> https://github.com/openbmc/phosphor-sel-logger/blob/3d300fca24b30864b3e9a4f5768cfe5e769458ae/include/sensorutils.hpp#L59
> >
> >
> > Hank
> >
> >
> > ________________________________
> > From: Patrick Venture <venture at google.com>
> > Sent: Friday, August 30, 2019 1:47 AM
> > To: Hank Liou (劉晉翰)
> > Cc: James Feist; openbmc at lists.ozlabs.org
> > Subject: Re: [phosphor-pid-control] scaling issue
> >
> > PTAL - https://gerrit.openbmc-project.xyz/24827 - this is merged, and
> > the srcrev bump should propagate into openbmc/openbmc in a day or two.
> >
> > On Wed, Aug 28, 2019 at 11:00 PM Hank Liou (劉晉翰) <Hank.Liou at quantatw.com>
> wrote:
> > >
> > > Hi Patrick,
> > >
> > > I think it's OK to parse the config min&max for temp sensors.
> > >
> > > Any suggestion?
> > >
> > > Thanks,
> > > Hank
> > >
> > > >-----Original Message-----
> > > >From: openbmc [mailto:openbmc-
> > > >bounces+hank.liou=quantatw.com at lists.ozlabs.org] On Behalf Of Hank
> Liou
> > > >(劉晉翰)
> > > >Sent: Friday, August 23, 2019 4:31 PM
> > > >To: Patrick Venture <venture at google.com>; James Feist
> > > ><james.feist at linux.intel.com>
> > > >Cc: openbmc at lists.ozlabs.org
> > > >Subject: RE: [phosphor-pid-control] scaling issue
> > > >
> > > >Hi Patrick,
> > > >
> > > >>-----Original Message-----
> > > >>From: Patrick Venture [mailto:venture at google.com]
> > > >>Sent: Wednesday, August 21, 2019 10:32 PM
> > > >>To: Hank Liou (劉晉翰) <Hank.Liou at quantatw.com>; James Feist
> > > >><james.feist at linux.intel.com>
> > > >>Cc: openbmc at lists.ozlabs.org
> > > >>Subject: Re: [phosphor-pid-control] scaling issue
> > > >>
> > > >>On Wed, Aug 21, 2019 at 1:11 AM Hank Liou (劉晉翰)
> > > >><Hank.Liou at quantatw.com> wrote:
> > > >>>
> > > >>> Hi All,
> > > >>>
> > > >>>
> > > >>> After commit [1], I found my temp sensor reading would be re-scaled
> > > >>> by
> > > >>multiplying 1 over 255, making temperature into unfamiliar unit. Also
> > > >>the fan rpm reading would lie in [0,1] interval, letting the fan
> input
> > > >>to be 0 (since the input value of fan is from an integer array [2]).
> Are these
> > > >normal behaviors?
> > > >>Or do I miss something?
> > > >>
> > > >>Are you using dbus configuration or json?  If json, can you attach
> your config.
> > > >>Since you're saying it was working and now isn't, I'm assuming
> there's
> > > >>something about the config being treated differently with the code
> > > >>changes in an unexpected way.
> > > >
> > > >I found pid control will first read min and max from dbus and then
> (before
> > > >commit [1]) revise them if
> > > >
> > > >info->min != conf::inheritValueFromDbus (in dbus/dbuspassive.cpp)
> > > >
> > > >After value initialization, the min and max would be the ones in json
> file (Json
> > > >file [3]). However, after commit [1] the min and max values of config
> would
> > > >not be fed into the fan control process. The scaling issue is
> originated from
> > > >commit [4] with the aim to treat fan rpm as percentage. It seems that
> commit
> > > >[1] unexpectedly affects temp sensors in the sense that the temp is
> the
> > > >integer reading not percentage. Before commit [1], it would not
> re-scale the
> > > >temp reading since my min and max are 0 [6].
> > > >
> > > >
> > > >
> > > >There is another issue with commit [1]. Now the fan rpm would be
> something
> > > >like
> > > >
> > > >1500 / 20000 = 0.075
> > > >
> > > >where rpm max 20000 is from dbus. However the fan input function would
> > > >transfer double into int, which is 0 for 0.075 (see [5]). Hence the
> fan input is 0
> > > >not percentage. Is there something wrong?
> > > >
> > > >[1] https://github.com/openbmc/phosphor-pid-
> > > >control/commit/fc2e803f5d9256944e18c7c878a441606b1f121c
> > > >[2] https://github.com/openbmc/phosphor-pid-
> > > >control/blob/a7ec8350d17b70153cebe666d3fbe88bddd02a1a/pid/fancontrolle
> > > >r.cpp#L86
> > > >[3]
> > > >       {
> > > >            "name": "fan1",
> > > >            "type": "fan",
> > > >            "readPath": "/sys/class/hwmon/hwmon1/fan1_input",
> > > >            "writePath": "/sys/class/hwmon/hwmon1/pwm1",
> > > >            "min": 0,
> > > >            "max": 255
> > > >        },
> > > >        {
> > > >            "name": "temp1",
> > > >            "type": "temp",
> > > >            "readPath":
> "/xyz/openbmc_project/sensors/temperature/temp1",
> > > >            "writePath": "",
> > > >            "min": 0,
> > > >            "max": 0
> > > >        }
> > > >[4] https://github.com/openbmc/phosphor-pid-
> > > >control/commit/75eb769d351434547899186f73ff70ae00d7934a
> > > >[5] https://github.com/openbmc/phosphor-pid-
> > > >control/blob/a7ec8350d17b70153cebe666d3fbe88bddd02a1a/pid/fancontrolle
> > > >r.cpp#L64
> > > >[6] https://github.com/openbmc/phosphor-pid-
> > > >control/blob/a7ec8350d17b70153cebe666d3fbe88bddd02a1a/dbus/dbuspassi
> > > >ve.cpp#L158
> > > >
> > > >>
> > > >>>
> > > >>>
> > > >>> [1]
> > > >>> https://github.com/openbmc/phosphor-pid-
> > > >>control/commit/fc2e803f5d92569
> > > >>> 44e18c7c878a441606b1f121c
> > > >>>
> > > >>> [2]
> > > >>> https://github.com/openbmc/phosphor-pid-
> > > >>control/blob/a7ec8350d17b70153
> > > >>> cebe666d3fbe88bddd02a1a/pid/fancontroller.cpp#L86
> > > >>>
> > > >>>
> > > >>> Thanks,
> > > >>>
> > > >>>
> > > >>> Hank Liou
> > > >>>
> > > >>> Quanta Computer Inc.
> > > >>>
> > > >>>
> > > >
> > > >Sincerely,
> > > >Hank
>


-- 
Regards,
Kun
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