linux-kernel - Re: "irq/matrix: Spread interrupts on allocation" breaks nouveau in mainline kernel

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Date:   Thu, 25 Jan 2018 21:12:13 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Lyude Paul <lyude@...hat.com>
cc:     "Ghannam, Yazen" <Yazen.Ghannam@....com>,
        "hpa@...or.com" <hpa@...or.com>,
        "keith.busch@...el.com" <keith.busch@...el.com>,
        "mingo@...nel.org" <mingo@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Borislav Petkov <bp@...en8.de>
Subject: Re: "irq/matrix: Spread interrupts on allocation" breaks nouveau in
 mainline kernel

On Thu, 25 Jan 2018, Lyude Paul wrote:
> On Thu, 2018-01-25 at 19:46 +0100, Thomas Gleixner wrote:
> > On Thu, 25 Jan 2018, Lyude Paul wrote:
> > 
> > > I think you are right, apologies. Glad to know this isn't a regression in
> > > the
> > > IRQ handling code :). It looks like our nouveau problems are probably coming
> > > from the fact that we don't just leave IRQs setup through suspend/resume
> > > which
> > > as far as I can tell, is probably not the correct thing to do.
> > 
> > If you tear down the interrupt, then you have to make sure that it's
> > completely masked and disabled on the device side (including MSI).
> Does this only need to be done if we handle irq_request()/irq_free() ourselves,
> or can we skip some of these steps if we let the kernel handle
> disabling/enabling IRQs during s/r?

If you do not free the interrupt on suspend, then the core does the right
thing. Though you should not inflict an interrupt storm in that case either :)

Thanks,

	tglx