linux-kernel - Re: [PATCH v14 4/9] acpi/arm64: Add GTDT table parse driver

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Date:   Fri, 11 Nov 2016 21:43:26 +0800
From:   Hanjun Guo <hanjun.guo@...aro.org>
To:     Fu Wei <fu.wei@...aro.org>, Mark Rutland <mark.rutland@....com>
CC:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <marc.zyngier@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        linux-arm-kernel@...ts.infradead.org,
        Linaro ACPI Mailman List <linaro-acpi@...ts.linaro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        rruigrok@...eaurora.org, "Abdulhamid, Harb" <harba@...eaurora.org>,
        Christopher Covington <cov@...eaurora.org>,
        Timur Tabi <timur@...eaurora.org>,
        G Gregory <graeme.gregory@...aro.org>,
        Al Stone <al.stone@...aro.org>, Jon Masters <jcm@...hat.com>,
        Wei Huang <wei@...hat.com>, Arnd Bergmann <arnd@...db.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
        Leo Duran <leo.duran@....com>,
        Wim Van Sebroeck <wim@...ana.be>,
        Guenter Roeck <linux@...ck-us.net>,
        linux-watchdog@...r.kernel.org, Tomasz Nowicki <tn@...ihalf.com>,
        Christoffer Dall <christoffer.dall@...aro.org>,
        Julien Grall <julien.grall@....com>
Subject: Re: [PATCH v14 4/9] acpi/arm64: Add GTDT table parse driver

On 10/26/2016 07:10 PM, Fu Wei wrote:
> Hi Mark,
>
> On 21 October 2016 at 00:37, Mark Rutland <mark.rutland@....com> wrote:
>> Hi,
>>
>> As a heads-up, on v4.9-rc1 I see conflicts at least against
>> arch/arm64/Kconfig. Luckily git am -3 seems to be able to fix that up
>> automatically, but this will need to be rebased before the next posting
>> and/or merging.
>>
>> On Thu, Sep 29, 2016 at 02:17:12AM +0800, fu.wei@...aro.org wrote:
>>> +static int __init map_gt_gsi(u32 interrupt, u32 flags)
>>> +{
>>> +     int trigger, polarity;
>>> +
>>> +     if (!interrupt)
>>> +             return 0;
>>
>> Urgh.
>>
>> Only the secure interrupt (which we do not need) is optional in this
>> manner, and (hilariously), zero appears to also be a valid GSIV, per
>> figure 5-24 in the ACPI 6.1 spec.
>>
>> So, I think that:
>>
>> (a) we should not bother parsing the secure interrupt
>
> If I understand correctly, from this point of view, kernel don't
> handle the secure interrupt.
> But the current arm_arch_timer driver still enable/disable/request
> PHYS_SECURE_PPI
> with PHYS_NONSECURE_PPI.
> That means we still need to parse the secure interrupt.
> Please correct me, if I misunderstand something? :-)
>
>> (b) we should drop the check above
>
> yes, if zero is a valid GSIV, this makes sense.
>
>> (c) we should report the spec issue to the ASWG
>>
>>> +/*
>>> + * acpi_gtdt_c3stop - got c3stop info from GTDT
>>> + *
>>> + * Returns 1 if the timer is powered in deep idle state, 0 otherwise.
>>> + */
>>> +bool __init acpi_gtdt_c3stop(void)
>>> +{
>>> +     struct acpi_table_gtdt *gtdt = acpi_gtdt_desc.gtdt;
>>> +
>>> +     return !(gtdt->non_secure_el1_flags & ACPI_GTDT_ALWAYS_ON);
>>> +}
>>
>> It looks like this can differ per interrupt. Shouldn't we check the
>> appropriate one?
>
> yes, I think you are right.

I think Mark already clarified this it's a global flag which defined
in the spec, and we don't need to update it.

Thanks
Hanjun