linux-kernel - Re: [Linaro-acpi] [PATCH v21 13/13] acpi/arm64: Add SBSA Generic Watchdog support in GTDT driver

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Date:   Tue, 21 Mar 2017 11:48:02 +0800
From:   Fu Wei <fu.wei@...aro.org>
To:     Mark Rutland <mark.rutland@....com>, Fu Wei <fu.wei@...aro.org>,
        Linaro ACPI Mailman List <linaro-acpi@...ts.linaro.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Wim Van Sebroeck <wim@...ana.be>, Wei Huang <wei@...hat.com>,
        Tomasz Nowicki <tn@...ihalf.com>,
        Timur Tabi <timur@...eaurora.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Len Brown <lenb@...nel.org>,
        "Abdulhamid, Harb" <harba@...eaurora.org>,
        Julien Grall <julien.grall@....com>,
        linux-watchdog@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        Marc Zyngier <marc.zyngier@....com>,
        Jon Masters <jcm@...hat.com>,
        Christopher Covington <cov@...eaurora.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-arm-kernel@...ts.infradead.org,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Christoffer Dall <christoffer.dall@...aro.org>
Subject: Re: [Linaro-acpi] [PATCH v21 13/13] acpi/arm64: Add SBSA Generic
 Watchdog support in GTDT driver

Hi Mark, Lurndal,


On 21 March 2017 at 02:50, Lurndal, Scott <Scott.Lurndal@...ium.com> wrote:
> On Mon, Mar 20, 2017 at 06:09:50PM +0000, 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 <mark.rutland@....com> wrote:
>> > > On Tue, Feb 07, 2017 at 02:50:15AM +0800, fu.wei@...aro.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.
>
>   It is a requirement of a conforming implementation that there
> be a generic watchdog (impl as per the appendix).   That doesn't preclude
> an implmentation from providing additional watchdogs (for example, if
> the processor implements EL3, it is likely that an implementation
> will include a secure watchdog as well as a non-secure watchdog).
>
>   The SBSA describes the minimal hardware requirements for a
> compliant server.

So I think, for the SBSA watchdog:

(1) there maybe more then one non-secure watchdog in GTDT

(2) we may also need to skip  secure watchdogs in GTDT,
and only register non-secure watchdogs into platform resources.

Please correct me, if I misunderstand something.

>
> scott



-- 
Best regards,

Fu Wei
Software Engineer
Red Hat