linux-kernel - Re: [PATCH 03/11] genirq: Export irq_set_affinity

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Message-ID: <3e73c85e-20d1-43ae-3c3a-04322ffa970e@gmail.com>
Date:   Mon, 27 Sep 2021 10:47:34 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Thomas Gleixner <tglx@...utronix.de>, Marc Zyngier <maz@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Russell King <linux@...linux.org.uk>,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        "maintainer:BROADCOM BCM281XX/BCM11XXX/BCM216XX ARM ARCHITE..." 
        <bcm-kernel-feedback-list@...adcom.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Mike Rapoport <rppt@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Arnd Bergmann <arnd@...db.de>,
        Guenter Roeck <linux@...ck-us.net>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Mark Rutland <mark.rutland@....com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Valentin Schneider <valentin.schneider@....com>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "moderated list:ARM PORT" <linux-arm-kernel@...ts.infradead.org>,
        "open list:SUPERH" <linux-sh@...r.kernel.org>,
        "open list:BROADCOM BMIPS MIPS ARCHITECTURE" 
        <linux-mips@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE" 
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH 03/11] genirq: Export irq_set_affinity_locked()

On 9/25/21 2:37 PM, Thomas Gleixner wrote:
> On Sat, Sep 25 2021 at 23:21, Thomas Gleixner wrote:
> 
>> On Sat, Sep 25 2021 at 12:48, Marc Zyngier wrote:
>>> On Fri, 24 Sep 2021 18:05:38 +0100, Florian Fainelli <f.fainelli@...il.com> wrote:
>>>>  }
>>>> +EXPORT_SYMBOL_GPL(irq_set_affinity_locked);
>>>
>>> This doesn't seem right.
>>>
>>> This driver seem to try and move interrupts on its own when the CPU
>>> goes down. Why can't it rely on the normal CPU hotplug infrastructure
>>> to do so like all the other drivers (bar some Cavium driver that does
>>> the same thing)?
>>>
>>> I'd rather you take this opportunity to move these drivers into the
>>> 21st century, so that we can kill irq_cpu_offline() and co altogether.
>>
>> I wanted to kill these callbacks years ago. Cavium has two variants of
>> those offline/online callbacks:
>>
>>  1) octeon_irq_cpu_offline_ciu() which is doing the same as that BCM
>>     driver. These really can go away. Just remove the callback and
>>     everything just works.
> 
> For BCM this works today when that chip is used on ARM[64] simply
> because the only architecture which invokes irq_cpu_offline() is MIPS.

That is correct. How would you recommend addressing that? In premise
when this driver is used on ARM[64] it is used as a second level
interrupt controller hanging off the ARM GIC (or another ARM CPU
interrupt controller), so in that case I suppose I could make the
irq_set_cpu_offline be dependent upon CONFIG_SMP and CONFIG_MIPS, would
that be acceptable?
-- 
Florian