linux-kernel - Re: [PATCH] pinctrl/amd: Use regular interrupt instead of chained

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Date:   Sun, 4 Jun 2017 15:49:40 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Linus Walleij <linus.walleij@...aro.org>
cc:     LKML <linux-kernel@...r.kernel.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        Borislav Petkov <bp@...en8.de>, Ken Xue <Ken.Xue@....com>,
        Marc Zyngier <marc.zyngier@....com>
Subject: Re: [PATCH] pinctrl/amd: Use regular interrupt instead of chained

On Mon, 29 May 2017, Linus Walleij wrote:

> On Tue, May 23, 2017 at 11:23 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
> 
> > The AMD pinctrl driver uses a chained interrupt to demultiplex the GPIO
> > interrupts. Kevin Vandeventer reported, that his new AMD Ryzen locks up
> > hard on boot when the AMD pinctrl driver is initialized. The reason is an
> > interrupt storm. It's not clear whether that's caused by hardware or
> > firmware or both.
> >
> > Using chained interrupts on X86 is a dangerous endavour. If a system is
> > misconfigured or the hardware buggy there is no safety net to catch an
> > interrupt storm.
> >
> > Convert the driver to use a regular interrupt for the demultiplex
> > handler. This allows the interrupt storm detector to catch the malfunction
> > and lets the system boot up.
> >
> > This should be backported to stable because it's likely that more users run
> > into this problem as the AMD Ryzen machines are spreading.
> >
> > Reported-by: Kevin Vandeventer
> > Link: https://bugzilla.suse.com/show_bug.cgi?id=1034261
> > Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> 
> Patch applied for fixes.
> 
> Hm, I wonder if there is a bunch of other x86 drivers that should just
> request the IRQ?

For sanity reasons I think so. chained interrupts are fine if you have
bootloader, device tree and kernel under control. Once BIOS/UEFI comes into
play the user is helpless against this kind of wreckage. We'll get that
same joy with ARM64 sooner than later.

Thanks,

	tglx