linux-kernel - Re: [PATCH v4 5/7] Watchdog: introduce ARM SBSA watchdog driver

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Message-ID: <20150914085137.GB22991@e104818-lin.cambridge.arm.com>
Date:	Mon, 14 Sep 2015 09:51:37 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Jon Masters <jcm@...hat.com>
Cc:	Timur Tabi <timur@...eaurora.org>,
	Guenter Roeck <linux@...ck-us.net>, fu.wei@...aro.org,
	Suravee.Suthikulpanit@....com, linaro-acpi@...ts.linaro.org,
	linux-watchdog@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
	tekkamanninja@...il.com, graeme.gregory@...aro.org,
	al.stone@...aro.org, hanjun.guo@...aro.org,
	ashwin.chaugule@...aro.org, arnd@...db.de, vgandhi@...eaurora.org,
	wim@...ana.be, leo.duran@....com, corbet@....net,
	mark.rutland@....com, will.deacon@....com, rjw@...ysocki.net
Subject: Re: [PATCH v4 5/7] Watchdog: introduce ARM SBSA watchdog driver

On Thu, Sep 10, 2015 at 06:45:17PM -0400, Jon Masters wrote:
> On 06/03/2015 02:53 PM, Timur Tabi wrote:
> > On 06/03/2015 01:25 PM, Guenter Roeck wrote:
> >> In general the idea here would be to use a crashdump kernel, which,
> >> when loaded, would reset the watchdog before it fires. This kernel
> >> would then write a core dump to a specified location.
> > 
> > What is the mechanism for resetting the watchdog?  The only code that 
> > knows about the hardware registers is this driver.  Does the crashdump 
> > kernel call the watchdog stop function?
> > 
> >> If arm64 doesn't support a crashdump kernel, it might still be possible
> >> to log the backtrace somewhere (eg in nvram using pstore if that is
> >> supported via acpi or efi).
> 
> Just to go back and explicitly answer this, arm64 does have support for
> crashdump, using the standard kexec/kdump approach, exactly as on x86.

Just a clarification - this is not (yet) supported in mainline, not even
with DT.

-- 
Catalin

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