linux-kernel - Re: [GIT pull] irq updates for 4.13

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Message-ID: <alpine.DEB.2.20.1707111951010.1799@nanos>
Date:   Tue, 11 Jul 2017 19:52:24 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
cc:     Tony Lindgren <tony@...mide.com>,
        Sebastian Reichel <sebastian.reichel@...labora.co.uk>,
        LKML <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Pavel Machek <pavel@....cz>,
        Linus Walleij <linus.walleij@...aro.org>,
        Grygorii Strashko <grygorii.strashko@...com>
Subject: Re: [GIT pull] irq updates for 4.13

On Tue, 11 Jul 2017, Linus Torvalds wrote:
> On Tue, Jul 11, 2017 at 9:19 AM, Thomas Gleixner <tglx@...utronix.de> wrote:
> >
> > What I do not understand here is that we have already power management
> > around all of that.
> >
> >        irq_chip_pm_get(&desc->irq_data);
> >        ...
> >        chip_bus_lock(desc);
> >        ...
> >        chip_bus_unlock_sync(desc);
> >        ...
> >        irq_chip_pm_put(&desc->irq_data);
> >
> > So why is that not sufficient and needs extra magic in that GPIO driver?
> 
> Well, irq_chip_pm_get/put() isn't called just over the operation, it's
> called over the *whole* sequence of the irq being enabled at all.
> 
> So the different (right now) is that
> 
>  - chip_bus_lock/unlock_sync() is purely done around the actual
> operations to set up and tear down the irq data.
> 
>    So this just covers the very short setup/teardown.
> 
>  - irq_chip_pm_get/put() is called around the *whole* "irqs can be active" block
> 
>    This covers the whole lifetime of the irq, from setup to free.
> 
> Very different.
> 
> I'd really prefer my simple patch for now, leaving everything working
> the way it used to work. I *think* it's ok for RT too. Yes?

Not completely, because of the free path issues. See the other mail. Tony
confirmed that it works. I wait for Sebastian and queue it with a proper
changelog, ok?

Thanks,

	tglx