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SubjectRe: [PATCH v21 13/13] acpi/arm64: Add SBSA Generic Watchdog support in GTDT driver
Hi Mark,

On 21 March 2017 at 02:09, Mark Rutland <> wrote:
> On Tue, Mar 21, 2017 at 01:57:58AM +0800, Fu Wei wrote:
>> On 18 March 2017 at 04:01, Mark Rutland <> wrote:
>> > On Tue, Feb 07, 2017 at 02:50:15AM +0800, 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?

I think we may can use "Timer Flags", because all the GSIV come with a flag,
if we can define a bit field called "valid" for all GSIV

Bit Field Bit Offset Number of bits Description
Valid 31 1 This bit
indicates the validity of the timer interrupt
Interrupt is valid
Interrupt is invalid
Then we don't need to test the value of GSIV, just test this bit instead.

Just my thought, hope this makes sense to all of you :-)

> 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.

Best regards,

Fu Wei
Software Engineer
Red Hat

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