linux-kernel - Re: [PATCH v7 0/8] Watchdog: introduce ARM SBSA watchdog driver

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Date:	Wed, 30 Sep 2015 22:43:38 +0530
From:	Pratyush Anand <panand@...hat.com>
To:	fu.wei@...aro.org
Cc:	Suravee.Suthikulpanit@....com, hanjun.guo@...aro.org,
	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, arnd@...db.de,
	linux@...ck-us.net, vgandhi@...eaurora.org, wim@...ana.be,
	jcm@...hat.com, leo.duran@....com, corbet@....net,
	mark.rutland@....com, catalin.marinas@....com, will.deacon@....com,
	rjw@...ysocki.net, dyoung@...hat.com
Subject: Re: [PATCH v7 0/8] Watchdog: introduce ARM SBSA watchdog driver

Hi Fu Wei,

On 25/08/2015:01:01:15 AM, fu.wei@...aro.org wrote:
> From: Fu Wei <fu.wei@...aro.org>
> 
> This patchset:
>     (1)Introduce Documentation/devicetree/bindings/watchdog/sbsa-gwdt.txt
>     for FDT info of SBSA Generic Watchdog, and give two examples of
>     adding SBSA Generic Watchdog device node into the dts files:
>     foundation-v8.dts and amd-seattle-soc.dtsi.
> 
>     (2)Introduce "pretimeout" into the watchdog framework, and update
>     Documentation/watchdog/watchdog-kernel-api.txt to introduce:
>         (1)the new elements in the watchdog_device and watchdog_ops struct;
>         (2)the new API "watchdog_init_timeouts".
> 
>     (3)Introduce ARM SBSA watchdog driver:
>         a.Use linux kernel watchdog framework;
>         b.Work with FDT on ARM64;
>         c.Use "pretimeout" in watchdog framework;
>         d.Support getting timeout and pretimeout from parameter and FDT
>           at the driver init stage.
>         e.In the first timeout, do panic to save system context;
>         f.In the second stage, user can still feed the dog without
>           cleaning WS0. By this feature, we can avoid the panic infinite
>           loops, while backing up a large system context in a server.
>         g.In the second stage, can trigger WS1 by setting pretimeout = 0
>           if necessary.
> 
>     (4)Introduce ACPI GTDT parser: drivers/acpi/gtdt.c
>     Parse SBSA Generic Watchdog Structure in GTDT table of ACPI,
>     and create a platform device with that information.
>     This platform device can be used by This Watchdog driver.
>     drivers/clocksource/arm_arch_timer.c is simplified by this GTDT support.
> 
> This patchset has been tested with watchdog daemon
> (ACPI/FDT, module/build-in) on the following platforms:
>     (1)ARM Foundation v8 model
> 

I tested it with kdump on fedora-arm64 Seattle platform. I enabled watchdog
using systemd (with 30s timeout), insured that watchdog is active and then
crashed the system. I can see that kdump kernel loads sbsa_wdt and activates
watchdog, still vmcore copy is done successfully.
My test kernel is here [1]

~Pratyush

[1] https://github.com/pratyushanand/linux/commits/wdt/sbsa-test-kexec 
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