linux-kernel - Re: [PATCH v23 09/11] acpi/arm64: Add memory-mapped timer support in GTDT driver

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Message-ID: <CADyBb7suSedttCma7Q6-RGfduJBOD5AWCpOA3pyvjDn6z+uSow@mail.gmail.com>
Date:   Fri, 7 Apr 2017 02:07:40 +0800
From:   Fu Wei <fu.wei@...aro.org>
To:     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>,
        Hanjun Guo <hanjun.guo@...aro.org>,
        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 v23 09/11] acpi/arm64: Add memory-mapped timer support in
 GTDT driver

Hi Mark,

On 7 April 2017 at 01:52, Mark Rutland <mark.rutland@....com> wrote:
> On Fri, Apr 07, 2017 at 01:39:09AM +0800, Fu Wei wrote:
>> On 7 April 2017 at 01:24, Mark Rutland <mark.rutland@....com> wrote:
>> > On Fri, Apr 07, 2017 at 12:47:47AM +0800, Fu Wei wrote:
>> >> On 6 April 2017 at 02:38, Mark Rutland <mark.rutland@....com> wrote:
>> >> > On Sat, Apr 01, 2017 at 01:51:03AM +0800, fu.wei@...aro.org wrote:
>
>> > However, I would prefer to simplify this such that we only free the
>> > IRQs in the error path.
>> >
>> > We should be able to iterate over all freams, freeing any non-zero
>> > interrupt, since !valid frames shouldn't have non-zero interrupts.
>>
>> Yes, that is what I am doing :
>>
>>  if (!frame->valid)
>>           continue;
>
> What I meant was that we won't look at the frame->valid flag at all;
> only the interrupts. e.g.
>
> for (int i = 0; i < ARCH_TIMER_MEM_MAX_FRAMES; i++) {
>         if (frame->phys_irq > 0)
>                 free_the_phys_irq_somehow();
>         if (frame->virt_irq > 0)
>                 free_the_virt_irq_somehow();
> }

Since we use "kcalloc" to allocate struct arch_timer_mem, this should be OK.

>
> ... where we somehow figure out the GSI, or we introduce an api like
> unregister_gsi_for_irq(irq).

Yes, If you are OK with introducing a new API , this problem is solved :-)

>
> Since the !valid frames should all have zero for their interrupt fields,
> no special handling is necessary.
>
> That way, we only free the IRQs in one place, it's obvious that we
> consistently free all of them, etc.
>
>> Lorenzo addressed the API issue, we may can fix it by getting GSI info
>> from DT, then register it until we figure the best frame.
>> It may need some big change in DT code
>
> I'd prefer to keep this constrained to the ACPI code. ;)
>
> Thanks,
> Mark.



-- 
Best regards,

Fu Wei
Software Engineer
Red Hat