thermal: support slope and offset coefficients

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>

diff --git a/Documentation/thermal/sysfs-api.txt b/Documentation/thermal/sysfs-api.txt
index 7d44d7f1a71bfdf2ff12beb662a2704312334738..c1f6864a8c5db86def7b40ca7746e028e99bf37a 100644 (file)
--- a/Documentation/thermal/sysfs-api.txt
+++ b/Documentation/thermal/sysfs-api.txt
@@ -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 *
 *****************************

diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index 962de1847cc08b40855df8c532e9f7e2d5ed0766..04659bfb888b73237257b75f944bf9130bc241b6 100644 (file)
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -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)

diff --git a/include/linux/thermal.h b/include/linux/thermal.h
index 6bbe11c97ceab740fed6bf1e9188d3f31ba9da96..037e9df2f6101bd70f2ad90e79e642599e56bc89 100644 (file)
--- a/include/linux/thermal.h
+++ b/include/linux/thermal.h
@@ -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 {