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Date: Mon, 20 Mar 2017 18:09:50 +0000
From: Mark Rutland <mark.rutland@arm.com>
To: Fu Wei <fu.wei@linaro.org>
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Subject: Re: [PATCH v21 13/13] acpi/arm64: Add SBSA Generic Watchdog support
 in GTDT driver
Message-ID: <20170320180949.GM31213@leverpostej>
References: <20170206185015.12296-1-fu.wei@linaro.org>
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 <20170317200153.GF15909@leverpostej>
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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.