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

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Message-ID: <CADyBb7uLiTg=FDe=HzXnKCWgO0y4DtJTOSBtgpm+5FbTH-6WSQ@mail.gmail.com>
Date:	Tue, 15 Sep 2015 11:16:28 +0800
From:	Fu Wei <fu.wei@...aro.org>
To:	Jon Masters <jcm@...hat.com>
Cc:	Timur Tabi <timur@...eaurora.org>,
	Guenter Roeck <linux@...ck-us.net>,
	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	Linaro ACPI Mailman List <linaro-acpi@...ts.linaro.org>,
	linux-watchdog@...r.kernel.org, devicetree@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>, linux-doc@...r.kernel.org,
	Wei Fu <tekkamanninja@...il.com>,
	G Gregory <graeme.gregory@...aro.org>,
	Al Stone <al.stone@...aro.org>,
	Hanjun Guo <hanjun.guo@...aro.org>,
	Ashwin Chaugule <ashwin.chaugule@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	Vipul Gandhi <vgandhi@...eaurora.org>,
	Wim Van Sebroeck <wim@...ana.be>,
	Leo Duran <leo.duran@....com>, Jon Corbet <corbet@....net>,
	Mark Rutland <mark.rutland@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Rafael Wysocki <rjw@...ysocki.net>
Subject: Re: [PATCH v4 5/7] Watchdog: introduce ARM SBSA watchdog driver

Hi Jon,

On 11 September 2015 at 06:45, Jon Masters <jcm@...hat.com> 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.
> There's still some more work to be done to get the ACPI case fully
> upstream (e.g. on X-Gene platforms such as the HP ProLiant Moonshot m400
> we need non-PSCI CPU parking protocol offlining when booting in
> UEFI/ACPI mode), but it's what we are doing in RHEL(SA) and the goal is
> to help clean up the remaining pieces upstream there.

Great thanks for your info.

I have tried kexec/kdump on a real aarch64 hardware, that works well.
Although it's still under development and upstreaming, the support is there.

After discussing with some kexec/kdump  developer, I think this driver
can cooperate with kexec/kdump.

>
> Jon.
>



-- 
Best regards,

Fu Wei
Software Engineer
Red Hat Software (Beijing) Co.,Ltd.Shanghai Branch
Ph: +86 21 61221326(direct)
Ph: +86 186 2020 4684 (mobile)
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