From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mark Rutland <mark.rutland@arm.com>
Subject: Re: [PATCH v21 13/13] acpi/arm64: Add SBSA Generic Watchdog support
 in GTDT driver
Date: Mon, 20 Mar 2017 18:09:50 +0000
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To: Fu Wei <fu.wei@linaro.org>
Cc: Linaro ACPI Mailman List <linaro-acpi@lists.linaro.org>, Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will.deacon@arm.com>, rruigrok@codeaurora.org, Wim Van Sebroeck <wim@iguana.be>, Wei Huang <wei@redhat.com>, Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>, Al Stone <al.stone@linaro.org>, Tomasz Nowicki <tn@semihalf.com>, Timur Tabi <timur@codeaurora.org>, Daniel Lezcano <daniel.lezcano@linaro.org>, ACPI Devel Maling List <linux-acpi@vger.kernel.org>, Guenter Roeck <linux@roeck-us.net>, Len Brown <lenb@kernel.org>, "Abdulhamid,
 Harb" <harba@codeaurora.org>, Julien Grall <julien.grall@arm.com>, linux-watchdog@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>, Marc Zyngier <marc.zyngier@arm.com>, Jon Masters <jcm@redhat.com>, Christopher Covington <cov@codeaurora.org>, Thomas Gleixner <tglx@linutronix.de>, linux-arm-kernel@lists.infradead.org, G Gregory <graeme.gre>
List-Id: linux-acpi@vger.kernel.org

On Tue, Mar 21, 2017 at 01:57:58AM +0800, Fu Wei wrote:
> On 18 March 2017 at 04:01, Mark Rutland <mark.rutland@arm.com> wrote:
> > On Tue, Feb 07, 2017 at 02:50:15AM +0800, fu.wei@linaro.org wrote:

> > I've not been able to find where the ACPI spec says that zero is not a
> > valid GSIV. This may simply be an oversight/ambiguity in the spec.
> >
> > Is there any statement to that effect?
> 
> you are right, zero is a  valid GSIV, I will delete this check. Thanks

That being the case, how does one describe a watchdog that does not have
an interrupt?

As I mentioned, I think this is an oversight/ambiguity in the spec tat
we should address.

> > My reading of SBSA is that there is one watchdog in the system.
> >
> > Is that not the case?
> 
> do you mean:
> ---------------
> 4.2.4 Watchdogs
> The base server system implements a Generic Watchdog as specified in
> APPENDIX A: Generic Watchdog.
> ---------------
> 
> I am not sure about that if this is saying "we only have one SBSA
> watchdog in a system"
> 
> would you let me know where mention it? Do I miss something?

My reading was that the 'a' above meant a single element. i.e.

	The base server system implements _a_ Generic Watchdog as
	specified in APPENDIX A: Generic Watchdog.

Subsequently in 4.2.5, it is stated:

	In this scenario, the system wakeup timer or generic watchdog is
	still required to send its interrupt.

... which only makes sense if there is a single watchdog in the system.

Perhaps this is an oversight in the specification.

Thanks,
Mark.