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

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Date:   Mon, 27 Sep 2021 20:18:36 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Florian Fainelli <f.fainelli@...il.com>,
        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 Mon, Sep 27 2021 at 10:47, Florian Fainelli wrote:
> On 9/25/21 2:37 PM, Thomas Gleixner wrote:
>>> 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?

Why? Just get rid of the callback in that driver and ensure that
irq_migrate_all_off_this_cpu() is invoked when the CPU dies.

arch/mips/kernel/smp-cps.c already does that, but I don't know whether
your MIPS platform uses those SMP ops. If not you surely have a template
there.

Thanks,

        tglx