linux-kernel - Re: [PATCH v1 00/12] qcom: dts: thermal cleanups

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Message-ID: <20190220233257.GA31479@localhost.localdomain>
Date:   Wed, 20 Feb 2019 15:32:59 -0800
From:   Eduardo Valentin <edubezval@...il.com>
To:     Amit Kucheria <amit.kucheria@...aro.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        DTML <devicetree@...r.kernel.org>
Subject: Re: [PATCH v1 00/12] qcom: dts: thermal cleanups

On Wed, Feb 20, 2019 at 03:09:36PM +0530, Amit Kucheria wrote:
> On Wed, Feb 20, 2019 at 6:56 AM Eduardo Valentin <edubezval@...il.com> wrote:
> >
> > Hey
> > On Mon, Feb 18, 2019 at 06:05:14PM +0530, Amit Kucheria wrote:
> > > - Expose all temperature sensors on msm8916, msm996, msm8998, sdm845
> > > - split up the register address map for msm8998
> > > - standardize names of the various thermal-zones across boards to make it
> > >   easy for test scripts to parse
> > >
> >
> > I am generally fine with the effort but please fix the following
> > (applies for the whole series) wrt to required properties for DT
> > thermal:
> > a. Trip points for your zones
> 
> Thanks for the review.
> 
> In some cases, the temperatures are just exposed so something in
> userspace might read it and do something with it. We don't expect
> kernel trips for them.

Would a hwmon driver make more sense here?

> 
> Adding trip points also requires me to add cooling-maps (your point b. below).

Yes.

> 
> I guess I'm looking for an example of how to just expose sensor
> temperatures w/o any associated trips and cooling maps.
> 
> > b. Cooling Mappings for zones that have passive trips.
> >
> 
> From what I can see currently only CPUs and GPUs (among the major heat
> sources) can passively reduce heat by reducing frequencies.
> 
> Things like cameras, display, video might have a more ON/OFF approach
> to throttling that might be controlled from userspace. And we don't
> have a way to tell in DT that these zones are managed in userspace

You can always add a Hot trip point. To my understanding that is for
notifying userspace.




> (https://patchwork.kernel.org/patch/10259487/)