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  1. 12 Aug, 2007 3 commits
    • Len Brown's avatar
      ACPI: thermal: create "thermal.psv=" to override passive trip points · a70cdc52
      Len Brown authored 
      "thermal.psv=-1" disables passive trip points
for all ACPI thermal zones.

"thermal.psv=C", where 'C' is degrees Celsius,
overrides all existing passive trip points
for all ACPI thermal zones.

thermal.psv is checked at module load time,
and in response to trip-point change events.

Note that if the system does not deliver thermal zone
temperature change events near the new trip-point,
then it will not be noticed.  To force your custom
trip point to be noticed, you may need to enable polling:
eg. thermal.tzp=3000 invokes polling every 5 minutes.

Note that once passive thermal throttling is invoked,
it has its own internal Thermal Sampling Period (_TSP),
that is unrelated to _TZP.

WARNING: disabling or raising a thermal trip point
may result in increased running temperature and
shorter hardware lifetime on some systems.
Signed-off-by: default avatarLen Brown <len.brown@intel.com>
      a70cdc52
    • Len Brown's avatar
      ACPI: thermal: expose "thermal.tzp=" to set global polling frequency · 730ff34d
      Len Brown authored 
      Thermal Zone Polling frequency (_TZP) is an optional ACPI object
recommending the rate that the OS should poll the associated thermal zone.

If _TZP is 0, no polling should be used.
If _TZP is non-zero, then the platform recommends that
the OS poll the thermal zone at the specified rate.
The minimum period is 30 seconds.
The maximum period is 5 minutes.

(note _TZP and thermal.tzp units are in deci-seconds,
 so _TZP = 300 corresponds to 30 seconds)

If _TZP is not present, ACPI 3.0b recommends that the
thermal zone be polled at an "OS provided default frequency".

However, common industry practice is:
1. The BIOS never specifies any _TZP
2. High volume OS's from this century never poll any thermal zones

Ie. The OS depends on the platform's ability to
provoke thermal events when necessary, and
the "OS provided default frequency" is "never":-)

There is a proposal that ACPI 4.0 be updated to reflect
common industry practice -- ie. no _TZP, no polling.

The Linux kernel already follows this practice --
thermal zones are not polled unless _TZP is present and non-zero.

But thermal zone polling is useful as a workaround for systems
which have ACPI thermal control, but have an issue preventing
thermal events.  Indeed, some Linux distributions still
set a non-zero thermal polling frequency for this reason.

But rather than ask the user to write a polling frequency
into all the /proc/acpi/thermal_zone/*/polling_frequency
files, here we simply document and expose the already
existing module parameter to do the same at system level,
to simplify debugging those broken platforms.

Note that thermal.tzp is a module-load time parameter only.
Signed-off-by: default avatarLen Brown <len.brown@intel.com>
      730ff34d
    • Len Brown's avatar
      ACPI: thermal: create "thermal.off=1" to disable ACPI thermal support · 72b33ef8
      Len Brown authored 
      "thermal.off=1" disables all ACPI thermal support at boot time.

CONFIG_ACPI_THERMAL=n can do this at build time.
"# rmmod thermal" can do this at run time,
as long as thermal is built as a module.

WARNING: On some systems, disabling ACPI thermal support
will cause the system to run hotter and reduce the
lifetime of the hardware.
Signed-off-by: default avatarLen Brown <len.brown@intel.com>
      72b33ef8
  3. 11 Aug, 2007 37 commits
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