Re: [PATCH v4 3/5] irqchip: Add DT binding doc for the virtual irq demuxer chip

[Rafael J. Wysocki]

On Wednesday, February 11, 2015 11:15:17 AM Mark Rutland wrote:
> On Wed, Feb 11, 2015 at 09:11:59AM +0000, Peter Zijlstra wrote:
> > On Tue, Feb 10, 2015 at 08:48:36PM +0000, Mark Rutland wrote:
> > > From f390ccbb31f06efee49b4469943c8d85d963bfb5 Mon Sep 17 00:00:00 2001
> > > From: Mark Rutland <mark.rutland@xxxxxxx>
> > > Date: Tue, 10 Feb 2015 20:14:33 +0000
> > > Subject: [PATCH] genirq: allow mixed IRQF_NO_SUSPEND requests
> > > 
> > > In some cases a physical IRQ line may be shared between devices from
> > > which we expect interrupts during suspend (e.g. timers) and those we do
> > > not (e.g. anything we cut the power to). Where a driver did not request
> > > the interrupt with IRQF_NO_SUSPEND, it's unlikely that it can handle
> > > being called during suspend, and it may bring down the system.
> > > 
> > > This patch adds logic to automatically mark the irqactions for these
> > > potentially unsafe handlers as disabled during suspend, leaving actions
> > > with IRQF_NO_SUSPEND enabled. If an interrupt is raised on a shared line
> > > during suspend, only the handlers requested with IRQF_NO_SUSPEND will be
> > > called. The handlers requested without IRQF_NO_SUSPEND will be skipped
> > > as if they had immediately returned IRQF_NONE.
> > > 
> > > Cc: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxxxxxxx>
> > > Cc: Jason Cooper <jason@xxxxxxxxxxxxxx>
> > > Cc: Nicolas Ferre <nicolas.ferre@xxxxxxxxx>
> > > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> > > Cc: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> > > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > > Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
> > 
> > Aw gawd.. not that again.
> 
> I agree this isn't pretty, but at least it doesn't require the HW
> description to know about Linux internals, and it can work for !DT
> systems.
> 
> I'm really not happy with placing Linux implementation details into
> DTBs.
> 
> > So Rafael and tglx went over this a few months ago I think:
> > 
> >   lkml.kernel.org/r/26580319.OZP7jvJnA9@xxxxxxxxxxxxxx
> > 
> > is the last series I could find. Maybe Rafael can summarize?
> 
> I can't get at any commentary from that link, unfortunately.
> 
> Rafael?

Well, the commentary is not there, because both I and Thomas implicitly agreed
on one thing: We cannot add any suspend-related checks to the interrupt handling
hot path, because that will affect everyone including people who don't use
suspend at all and who *really* care about interrupt handling performance.

Rafael

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