ACPI: thermal: create "thermal.psv=" to override passive trip points

"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: Len Brown <len.brown@intel.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index ed7d7913af8c..52e1c2d26a25 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1823,6 +1823,10 @@ and is between 256 and 4096 characters. It is defined in the file
 	thermal.off=	[HW,ACPI]
 			1: disable ACPI thermal control
 
+	thermal.psv=	[HW,ACPI]
+			-1: disable all passive trip points
+			<degrees C>: override all passive trip points to this value
+
 	thermal.tzp=	[HW,ACPI]
 			Specify global default ACPI thermal zone polling rate
 			<deci-seconds>: poll all this frequency