linux-kernel - Re: [PATCH 1/2] thermal: support slope and offset coefficients

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Date:	Mon, 11 May 2015 20:25:10 -0700
From:	Eduardo Valentin <edubezval@...il.com>
To:	Rui Zhang <rui.zhang@...el.com>, hongtao.jia@...escale.com,
	kong.kongxinwei@...ilicon.com, nrajan@...eaurora.org
Cc:	Linux PM <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux ACPI <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH 1/2] thermal: support slope and offset coefficients

Copying Narendran.

On Mon, May 11, 2015 at 08:04:16PM -0700, Eduardo Valentin wrote:
> 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@...il.com>
> ---
>  Documentation/thermal/sysfs-api.txt | 16 ++++++++++++++++
>  drivers/thermal/thermal_core.c      |  4 ++++
>  include/linux/thermal.h             | 11 +++++++++++
>  3 files changed, 31 insertions(+)
> 
> diff --git a/Documentation/thermal/sysfs-api.txt b/Documentation/thermal/sysfs-api.txt
> index 7d44d7f..c1f6864 100644
> --- 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 962de18..04659bf 100644
> --- 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 6bbe11c..037e9df 100644
> --- 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 {
> -- 
> 2.3.4
> 

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