linux-kernel - Re: Interrupt storm from pinctrl-amd on Acer AN515-42

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Date:   Tue, 8 Jan 2019 16:01:33 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Linus Walleij <linus.walleij@...aro.org>
cc:     Leonard Crestez <cdleonard@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Daniel Kurtz <djkurtz@...omium.org>,
        Nehal Shah <Nehal-bakulchandra.Shah@....com>,
        Shyam Sundar S K <Shyam-sundar.S-k@....com>,
        Daniel Drake <drake@...lessm.com>,
        Nitesh Kumar Agrawal <Nitesh-kumar.Agrawal@....com>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Hans de Goede <hdegoede@...hat.com>
Subject: Re: Interrupt storm from pinctrl-amd on Acer AN515-42

On Fri, 28 Dec 2018, Linus Walleij wrote:

> On Fri, Dec 28, 2018 at 12:02 AM Leonard Crestez <cdleonard@...il.com> wrote:
> 
> > Digging a little deeper it seems the touchpad interrupt is active on
> > boot and since it's configured as "level" and no touchpad driver is
> > available yet there does not seem to be any way to clear it.
> 
> I think these are called "spurious interrupts".
> 
> > I don't know how this should be handled, booting with an active enabled but
> > unclearable interrupt seems like a platform bug to me. There is even an
> > option to set touchpad to "basic" which does some sort of ps2 emulation
> > but the IRQ issue still happens!
> >
> > One workaround is to explicitly disable the interrupt from the handler
> > if no mapping is found; this will keep it disabled until
> > amd_gpio_irq_set_type is called later.
> 
> I don't know how x86 and ACPI systems usually deal with this stuff
> so I'm kind of lost. On the embedded systems that I develop on,
> I would just disable all interrupts on probe() (usually writing 0x0 in
> some interrupt enable register) and then they will get enabled
> once consumers need them.

That's the right thing to do.

> But I have come to understand that maybe ACPI systems are
> not so happy about drivers doing things like that?

Each driver has to invoke a request_irq() variant, which enables the
interrupt line. So there should be no problem when disabling all interrupts
on probe.

Thanks,

	tglx