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thermal: support slope and offset coefficients

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It is common to have a linear extrapolation from
the current sensor readings and the actual temperature
value. This is specially the case when the sensor
is in use to extrapolate hotspots.

This patch adds slope and offset constants for
single sensor linear extrapolation equation. Because
the same sensor can be use in different locations,
from board to board, these constants are added
as part of thermal_zone_params.

The constants are available through sysfs.

It is up to the device driver to determine
the usage of these values.

Signed-off-by: Eduardo Valentin <edubezval@gmail.com>
This commit is contained in:
Eduardo Valentin 2015-05-11 19:34:23 -07:00
parent ea54cac906
commit 9d0be7f481
3 changed files with 31 additions and 0 deletions
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16
Documentation/thermal/sysfs-api.txt
View File

@ -190,6 +190,8 @@ Thermal zone device sys I/F, created once it's registered:
|---k_i: PID's integral term in the power allocator gov
|---k_d: PID's derivative term in the power allocator
|---integral_cutoff: Offset above which errors are accumulated
|---slope: Slope constant applied as linear extrapolation
|---offset: Offset constant applied as linear extrapolation
Thermal cooling device sys I/F, created once it's registered:
/sys/class/thermal/cooling_device[0-*]:
@ -359,6 +361,20 @@ integral_cutoff
Documentation/thermal/power_allocator.txt
RW, Optional
slope
The slope constant used in a linear extrapolation model
to determine a hotspot temperature based off the sensor's
raw readings. It is up to the device driver to determine
the usage of these values.
RW, Optional
offset
The offset constant used in a linear extrapolation model
to determine a hotspot temperature based off the sensor's
raw readings. It is up to the device driver to determine
the usage of these values.
RW, Optional
*****************************
* Cooling device attributes *
*****************************

4
drivers/thermal/thermal_core.c
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@ -944,6 +944,8 @@ create_s32_tzp_attr(k_pu);
create_s32_tzp_attr(k_i);
create_s32_tzp_attr(k_d);
create_s32_tzp_attr(integral_cutoff);
create_s32_tzp_attr(slope);
create_s32_tzp_attr(offset);
#undef create_s32_tzp_attr
static struct device_attribute *dev_tzp_attrs[] = {
@ -953,6 +955,8 @@ static struct device_attribute *dev_tzp_attrs[] = {
&dev_attr_k_i,
&dev_attr_k_d,
&dev_attr_integral_cutoff,
&dev_attr_slope,
&dev_attr_offset,
};
static int create_tzp_attrs(struct device *dev)

11
include/linux/thermal.h
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@ -302,6 +302,17 @@ struct thermal_zone_params {
/* threshold below which the error is no longer accumulated */
s32 integral_cutoff;
/*
* @slope: slope of a linear temperature adjustment curve.
* Used by thermal zone drivers.
*/
int slope;
/*
* @offset: offset of a linear temperature adjustment curve.
* Used by thermal zone drivers (default 0).
*/
int offset;
};
struct thermal_genl_event {