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    SubjectRE: thermal governor: does it actually work??
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    > -----Original Message-----
    > From: Andreas Mohr [mailto:andi@lisas.de]
    > Sent: Thursday, February 14, 2013 11:33 PM
    > To: linux-kernel@vger.kernel.org
    > Cc: R, Durgadoss; Zhang, Rui; peter@piie.net
    > Subject: thermal governor: does it actually work??
    > Importance: High
    >
    > For me after having loaded acerhdf the fan never stops (with kernelmode
    > active), despite staying safely below trip point
    > (acerhdf_set_cur_state() actually never gets called).

    Please attach the output of
    "grep . /sys/class/thermal/thermal_zone*/cdev*/*"?

    > And AFAIR in a 3.2.0 kernel acerhdf fan operation seemed to just work
    > (i.e., no fan for low temps, from the beginning).
    > Needless to say 3.2.0 didn't even feature all the modern thermal
    > governor crapyard yet ;) (ok, well, it's more complex but it's also a
    > very nice environment capability)
    >
    > 3.8-rc7:
    > CONFIG_ACPI_THERMAL=m
    > CONFIG_THERMAL=m
    > CONFIG_THERMAL_HWMON=y
    > CONFIG_THERMAL_DEFAULT_GOV_STEP_WISE=y
    > # CONFIG_THERMAL_DEFAULT_GOV_FAIR_SHARE is not set #
    > CONFIG_THERMAL_DEFAULT_GOV_USER_SPACE is not set CONFIG_FAIR_SHARE=y
    > CONFIG_STEP_WISE=y # CONFIG_USER_SPACE is not set # CONFIG_CPU_THERMAL
    > is not set
    >
    >
    >
    > Terminology in this area seems to be quite a bit off, too, at several
    > docs places, at least according to my understanding:
    >
    > e.g. drivers/thermal/step_wise.c has the following comment:
    >
    > /**
    > * step_wise_throttle - throttles devices associated with the given
    > zone
    > * @tz - thermal_zone_device
    > * @trip - the trip point
    > * @trip_type - type of the trip point
    > *
    > * Throttling Logic: This uses the trend of the thermal zone to
    > * throttle.
    > * If the thermal zone is 'heating up' this throttles all the cooling
    > * devices associated with the zone and its particular trip point, by
    > * one
    > * step. If the zone is 'cooling down' it brings back the performance
    > of
    > * the devices by one step.
    >
    >
    >
    > if ... heating up ... throttles ...
    > Sorry, but at least for P4 clockmod stuff (or some such), throttle
    > states (P1...P8 IIRC) meant that the CPU operation was *reduced*, i.e.
    > with pause intervals.

    For processors, surely you are right.

    > And the translation of throttle clearly says that it does go that way
    > and not the other way...
    > (yes, you managed to confuse me that much that I even had to look up
    > things to verify)
    >

    The question is that if we can also call it "throttle" when reducing the device performance to generate less heat.

    I do not have a clear answer for this as I'm not a native English speaker.
    And what you're saying here may be right.
    Surely I can generate a patch to rename it if throttle can't be used in that way.

    Len,
    What's your idea on this?

    Thanks,
    rui
    > ... cooling down ... brings back ...
    > This should certainly be worded "reduces" or some such.
    >
    > So, any idea why I'm missing callbacks in acerhdf (if that is what I'm
    > supposed to expect to happen)?
    > Kernel bug, .config mistake, missing/wrong user-side setup?
    >
    > Needless to say if kernel bug this ought to be fixed pre-3.8 ideally.
    >
    > Thanks,
    >
    > Andreas Mohr


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