linux-kernel - Re: [PATCH] thermal: of: Allow selection of thermal governor in DT

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Message-ID: <CAP245DWvBjcS73YhPxwh2OKW_PYvBLTe-ay6XD8VrSWpukQ3CQ@mail.gmail.com>
Date:   Tue, 6 Mar 2018 11:18:15 +0530
From:   Amit Kucheria <amit.kucheria@...aro.org>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     DTML <devicetree@...r.kernel.org>,
        Ram Chandrasekar <rkumbako@...eaurora.org>,
        Lina Iyer <ilina@...eaurora.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Eduardo Valentin <edubezval@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Linux PM list <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] thermal: of: Allow selection of thermal governor in DT

On Tue, Mar 6, 2018 at 2:41 AM, Daniel Lezcano
<daniel.lezcano@...aro.org> wrote:
> On 05/03/2018 19:36, Amit Kucheria wrote:
>> From: Ram Chandrasekar <rkumbako@...eaurora.org>
>>
>> There is currently no way for the governor to be selected for each thermal
>> zone in devicetree. This results in the default governor being used for all
>> thermal zones even though no such restriction exists in the core code.
>>
>> Add support for specifying the thermal governor to be used for a thermal
>> zone in the devicetree. The devicetree config should specify the governor
>> name as a string that matches any available governors. If not specified, we
>> maintain the current behaviour of using the default governor.
>>
>> Signed-off-by: Ram Chandrasekar <rkumbako@...eaurora.org>
>> Signed-off-by: Amit Kucheria <amit.kucheria@...aro.org>
>
> Why not create a kernel parameter (eg. thermal.governor=) ? So everyone
> can gain benefit of this feature. And in order to specify that from the
> DT, add the 'chosen' node and bootargs with the desired kernel parameter?
>

This is supposed to be a per-thermal zone property. So specifying it
on the command-line, while possible, might be a little cumbersome. I'm
not even sure if kernel parameters can have a variable number of
arguments. IOW, thermal.tz0.governor=userspace,
thermal.tz1.governor=step_wise, thermal.tz2.governor=userspace, .....

I'm already seeing SoCs defining 8 or more thermal zones.