linux-kernel - Re: [PATCH v10 5/5] Watchdog: ARM SBSA Generic Watchdog half timeout panic support

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Date:	Wed, 3 Feb 2016 12:08:59 -0600
From:	Timur Tabi <timur@...eaurora.org>
To:	Fu Wei <fu.wei@...aro.org>
Cc:	Rob Herring <robh+dt@...nel.org>,
	Paweł Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Wim Van Sebroeck <wim@...ana.be>,
	Guenter Roeck <linux@...ck-us.net>,
	Jon Corbet <corbet@....net>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-watchdog@...r.kernel.org, linux-doc@...r.kernel.org,
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Linaro ACPI Mailman List <linaro-acpi@...ts.linaro.org>,
	rruigrok@...eaurora.org, "Abdulhamid, Harb" <harba@...eaurora.org>,
	Christopher Covington <cov@...eaurora.org>,
	Dave Young <dyoung@...hat.com>,
	Pratyush Anand <panand@...hat.com>,
	G Gregory <graeme.gregory@...aro.org>,
	Al Stone <al.stone@...aro.org>,
	Hanjun Guo <hanjun.guo@...aro.org>,
	Jon Masters <jcm@...hat.com>, Arnd Bergmann <arnd@...db.de>,
	Leo Duran <leo.duran@....com>, sudeep.holla@....com
Subject: Re: [PATCH v10 5/5] Watchdog: ARM SBSA Generic Watchdog half timeout
 panic support

Fu Wei wrote:
> Actually I am taking your suggestion to avoid touching WCV in
> interrupt routine.
> So even we have pre-timeout support , it is useless for this
> panic-on-half-timeout feature,
> because pre-timeout  == timeout / 2 (always).
>
> So maybe I misunderstand your suggestion,
> could you let me know : why we want pre-timeout here?

Maybe I'm confused.

For pre-timeout, I think the SBSA watchdog driver should support only 
half-timeout.  That is, the user cannot configure the length of the 
pre-timeout with this driver.  He can only enable it, and it is 
automatically set to 1/2 timeout.

So when pre-timeout occurs, the interrupt handler calls panic() or 
whatever it's supposed to do.

So "pre-timeout  == timeout / 2 (always)" is exactly what we want.