linux-kernel - Re: [PATCH v2 1/5] thermal: change "hysteresis" as optional property

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Date:	Sun, 20 Mar 2016 23:40:31 +0800
From:	Leo Yan <leo.yan@...aro.org>
To:	Javi Merino <javi.merino@....com>
Cc:	Eduardo Valentin <edubezval@...il.com>,
	Wei Xu <xuwei5@...ilicon.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Zhang Rui <rui.zhang@...el.com>,
	kongxinwei <kong.kongxinwei@...ilicon.com>,
	Punit Agrawal <Punit.Agrawal@....com>,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH v2 1/5] thermal: change "hysteresis" as optional property

Hi Javi,

Sorry for late response.

On Wed, Mar 09, 2016 at 11:10:52AM +0000, Javi Merino wrote:
> On Tue, Mar 08, 2016 at 12:55:59PM -0800, Eduardo Valentin wrote:
> > On Tue, Mar 08, 2016 at 09:57:43PM +0800, Leo Yan wrote:

[...]

> > > > > > > The property "hysteresis" is mandatory for trip points, so if without
> > > > > > > it the thermal zone cannot register successfully. But "hysteresis" is
> > > > > > > ignored in the thermal subsystem and only inquired by several thermal
> > > > > > > sensor drivers.
> > > > > > 
> > > > > > If the Linux thermal subsystem has a problem with handling hysteresis, I
> > > > > > would rather fix Linux code than relaxing the DT binding. Or if you
> > > > > > still believe hysteresis is really optional, I would prefer to see a
> > > > > > better justification than "Linux ignores it".
> > > > 
> > > > I see it the other way round, Is hysteresis a property that, without
> > > > it, the thermal code can't configure itself so it fails to create the
> > > > trip point?  The current code goes "There is no hysteresis for this
> > > > property, I don't know how to set up this trip point!".  I think we
> > > > can do better than this.
> > > 
> > > Do you agree with Javi's suggestion? If you think it's okay, I will
> > > move on to send out a new version patch based on Javi's comments.
> > 
> > No I don't. This discussion so far has been about Linux code. I still
> > havent seen an argument explaining why hysteresis has to be optional.
> 
> Fair enough.  Looks like I'm holding this driver from being
> upstreamed, so I'll back off.
> 
> Leo, sorry for misguiding you.  Please bring back the hysteresis
> property you had in v1.

Not at all. I will add back hysteresis property and resend new patches.

Thanks,
Leo Yan