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Date: Thu, 3 Mar 2016 08:29:44 -0800
From: Eduardo Valentin <edubezval@...il.com>
To: Leo Yan <leo.yan@...aro.org>
Cc: 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>,
Javi Merino <javi.merino@....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 Leo,
On Fri, Feb 26, 2016 at 11:43:43AM +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.
I am not sure this a good direction to go. Remember that Linux
implementation not necessarily has to be the implication of the DT
binding. Hysteresis is a property that plays a significant role on
thermal control systems, which in many cases avoid overshooting cooling
actions. Having the DT writer to explicitly set it to 0 means that zone
does not suffer of overshooting and does not need hysteresis.
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".
BR,
Eduardo
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