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>

2 files changed, 18 insertions, 3 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
diff --git a/drivers/acpi/thermal.c b/drivers/acpi/thermal.c
index b6b3bec84547..74e25be8abc9 100644
--- a/drivers/acpi/thermal.c
+++ b/drivers/acpi/thermal.c
@@ -82,6 +82,10 @@ static int off;
 module_param(off, int, 0);
 MODULE_PARM_DESC(off, "Set to disable ACPI thermal support.\n");
 
+static int psv;
+module_param(psv, int, 0644);
+MODULE_PARM_DESC(psv, "Disable or override all passive trip points.\n");
+
 static int acpi_thermal_add(struct acpi_device *device);
 static int acpi_thermal_remove(struct acpi_device *device, int type);
 static int acpi_thermal_resume(struct acpi_device *device);
@@ -343,9 +347,16 @@ static int acpi_thermal_get_trip_points(struct acpi_thermal *tz)
 
         /* Passive: Processors (optional) */
 
-        status =
-            acpi_evaluate_integer(tz->device->handle, "_PSV", NULL,
-                                  &tz->trips.passive.temperature);
+        if (psv == -1) {
+                status = AE_SUPPORT;
+        } else if (psv > 0) {
+                tz->trips.passive.temperature = CELSIUS_TO_KELVIN(psv);
+                status = AE_OK;
+        } else {
+                status = acpi_evaluate_integer(tz->device->handle,
+                        "_PSV", NULL, &tz->trips.passive.temperature);
+        }
+
         if (ACPI_FAILURE(status)) {
                 tz->trips.passive.flags.valid = 0;
                 ACPI_DEBUG_PRINT((ACPI_DB_INFO, "No passive threshold\n"));