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

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Date:	Wed, 11 Feb 2015 15:31:18 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Mark Rutland <mark.rutland@....com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <Pawel.Moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 3/5] irqchip: Add DT binding doc for the virtual irq demuxer chip

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@....com>
> > > 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@...e-electrons.com>
> > > Cc: Jason Cooper <jason@...edaemon.net>
> > > Cc: Nicolas Ferre <nicolas.ferre@...el.com>
> > > Cc: Peter Zijlstra <peterz@...radead.org>
> > > Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > Cc: Thomas Gleixner <tglx@...utronix.de>
> > > Signed-off-by: Mark Rutland <mark.rutland@....com>
> > 
> > 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@...tro.rjw.lan
> > 
> > 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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