linux-kernel - Re: [PATCH 3/5] irqchip: armada-370-xp: re-enable per-CPU interrupts at resume time

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Message-ID: <20151026011036.2cb5b7a8@free-electrons.com>
Date:	Mon, 26 Oct 2015 01:10:36 +0100
From:	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
To:	Marcin Wojtas <mw@...ihalf.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Marc Zyngier <marc.zyngier@....com>,
	Lior Amsalem <alior@...vell.com>, Andrew Lunn <andrew@...n.ch>,
	Tawfik Bayouk <tawfik@...vell.com>,
	linux-kernel@...r.kernel.org, Nadav Haklai <nadavh@...vell.com>,
	Gregory Clement <gregory.clement@...e-electrons.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
Subject: Re: [PATCH 3/5] irqchip: armada-370-xp: re-enable per-CPU
 interrupts at resume time

Marcin,

On Sun, 25 Oct 2015 22:22:37 +0100, Marcin Wojtas wrote:

> > @@ -550,16 +572,27 @@ static void armada_370_xp_mpic_resume(void)
> >                 if (virq == 0)
> >                         continue;
> >
> > -               if (irq != ARMADA_370_XP_TIMER0_PER_CPU_IRQ)
> > +               data = irq_get_irq_data(virq);
> > +
> > +               if (irq != ARMADA_370_XP_TIMER0_PER_CPU_IRQ) {
> > +                       /* Non per-CPU interrupts */
> >                         writel(irq, per_cpu_int_base +
> 
> For "Non per-CPU interrupts" per_cpu_int_base is used - is it
> intentional? In armada_370_xp_irq_mask/unmask the condition looks
> exactly opposite...

Yes, this is normal. Carefully read PATCH 5/5, which adds a big
comment, which explains the logic of the HW and how the
irq-armada-370-xp driver copes with it.

Each interrupt can be masked at two levels. One level is enabled when
the interrupted is mapped, the other upon ->mask()/->unmask(). So
when we're resuming, we need to re-enable the interrupt at the level it
was enabled in ->map(), and have ->mask()/->unmask() continue to
mask/unmask the interrupt at the other level.

For per-CPU interrupts, ->map() and ->resume() enable the interrupt at
the global level, and leave ->mask()/->unmask() enable/disable at the
per-CPU level.

For global interrupts, ->map() and ->resume() enable the interrupt at
the per-CPU level, and leave ->mask()/->unmask() enable/disable at the
global level.

Again, see PATCH 5/5, and let me know if there are still some unclear
aspects.

Thanks!

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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