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Date: Wed, 18 Feb 2015 16:21:23 +0000
From: Javi Merino <javi.merino@arm.com>
To: Eduardo Valentin <edubezval@gmail.com>
Cc: Rui Zhang <rui.zhang@intel.com>,
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Subject: Re: [PATCH RFC 12/12] Documentation: thermal docbook: introduce
 governor chapter
Message-ID: <20150218162123.GA16442@e104805>
References: <1423517653-11359-1-git-send-email-edubezval@gmail.com>
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Hi Eduardo,

On Mon, Feb 09, 2015 at 09:34:13PM +0000, Eduardo Valentin wrote:
> In this patch we add a chapter in the thermal docbook to
> describe the existing governors. The chapter contains
> one section per governor.
> 
> Each governor description includes the respective code documentation.
> Each governor section contains a description of the governor
> logic.
> 
> Signed-off-by: Eduardo Valentin <edubezval@gmail.com>
> ---
>  Documentation/DocBook/thermal.tmpl | 67 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 67 insertions(+)
> 
> diff --git a/Documentation/DocBook/thermal.tmpl b/Documentation/DocBook/thermal.tmpl
> index d6ebbea..cf1a198 100644
> --- a/Documentation/DocBook/thermal.tmpl
> +++ b/Documentation/DocBook/thermal.tmpl
> @@ -212,6 +212,73 @@
>  			</glossary>
>  		</sect1>
>  	</chapter>
> +
> +	<chapter id="governors">
> +		<title>Thermal Governors</title>
> +		<para>
> +		</para>
> +
> +		<sect1 id="step_wise">
> +			<title>step_wise Thermal Governor</title>
> +			<para>Step Wise uses the trend of the thermal zone to
> +			throttle. If the thermal zone is 'heating up' this
> +			throttles all the cooling devices associated with the
> +			zone and its particular trip point, by one step. If the
> +			zone is 'cooling down' it brings back the performance
> +			of the devices by one step.
> +			</para>
> +!Idrivers/thermal/step_wise.c
> +!Pdrivers/thermal/step_wise.c Algorithm
> +		</sect1>
> +		<sect1 id="fair_share">
> +			<title>fair_share Thermal Governor</title>
> +			<para>Fair Share Governor uses three parameters to
> +			calculate the new throttle state of the cooling devices
> +			associated with the given zone.  Parameters used for
> +			Throttling:
> +			</para>
> +			<itemizedlist mark='opencircle'>
> +				<listitem>P1. max_state: Maximum throttle state
> +				exposed by the cooling device.</listitem>
> +				<listitem>P2. weight[i]/100:</listitem>
> +				<listitem>How 'effective' the 'i'th device is,
> +				in cooling the given zone.</listitem>
> +				<listitem>P3.
> +				cur_trip_level/max_no_of_trips:</listitem>
> +			</itemizedlist>
> +			<para>This describes the extent to which the devices
> +			should be throttled. We do not want to throttle too
> +			much when we trip a lower temperature, whereas the
> +			throttling is at full swing if we trip critical levels.
> +			Heavily assumes the trip points are in ascending order
> +			new_state of cooling device = P3 * P2 * P1.
> +			</para>

This seems to be heavily based on the kerneldoc in fair_share.c .
Wouldn't it be better to do a similar trick to what you did in
step_wise?  That is, move that kerneldoc into an "Algorithm" entry and
include it here.  That way we avoid the duplication of the
documentation.

Cheers,
Javi

> +!Idrivers/thermal/fair_share.c
> +		</sect1>
> +		<sect1 id="bang_bang">
> +			<title>bang_bang Thermal Governor</title>
> +			<para>The Bang Bang Governor has a two point regulation
> +			logic, deliver cooling state depending on the previous
> +			state shown in this diagram: </para>
> +			<para>If the fan is not running and temperature exceeds
> +			trip_temp, the fan gets turned on. In case the fan is
> +			running, temperature must fall below (trip_temp - hyst)
> +			so that the fan gets turned off again.
> +			</para>
> +!Idrivers/thermal/gov_bang_bang.c
> +		</sect1>
> +		<sect1 id="user_space">
> +			<title>user_space Thermal Governor</title>
> +			<para> The User Space governor is outside the Kernel.
> +			The Thermal Framework hands off the entire control to
> +			userland if the User Space governor is assigned to a
> +			thermal zone. A KOBJ_CHANGE UEvent notification is sent
> +			to userland whenever a governor needs to take an
> +			action.
> +			</para>
> +!Idrivers/thermal/user_space.c
> +		</sect1>
> +	</chapter>
>  	<chapter id="api">
>  	<title>Thermal Device Driver Writer API reference</title>
>  		<para> This Chapter contains an API reference for Thermal driver writers.
> -- 
> 2.1.3
> 
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