linux-kernel - Re: [PATCH V4 3/9] irqdomain: Don't set type when mapping an IRQ

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Date:	Sat, 4 Jun 2016 10:51:55 +0100
From:	Marc Zyngier <marc.zyngier@....com>
To:	Jon Hunter <jonathanh@...dia.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Rob Herring <robh+dt@...nel.org>,
	"Pawel Moll" <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	"Stephen Warren" <swarren@...dotorg.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Kevin Hilman <khilman@...nel.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Grygorii Strashko <grygorii.strashko@...com>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Linus Walleij <linus.walleij@...aro.org>,
	<linux-tegra@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V4 3/9] irqdomain: Don't set type when mapping an IRQ

On Thu, 12 May 2016 16:19:26 +0100
Jon Hunter <jonathanh@...dia.com> wrote:

> Some IRQ chips, such as GPIO controllers or secondary level interrupt
> controllers, may require require additional runtime power management
> control to ensure they are accessible. For such IRQ chips, it makes sense
> to enable the IRQ chip when interrupts are requested and disabled them
> again once all interrupts have been freed.
> 
> When mapping an IRQ, the IRQ type settings are read and then programmed.
> The mapping of the IRQ happens before the IRQ is requested and so the
> programming of the type settings occurs before the IRQ is requested. This
> is a problem for IRQ chips that require additional power management
> control because they may not be accessible yet. Therefore, when mapping
> the IRQ, don't program the type settings, just save them and then program
> these saved settings when the IRQ is requested (so long as if they are not
> overridden via the call to request the IRQ).
> 
> Add a stub function for irq_domain_free_irqs() to avoid any compilation
> errors when CONFIG_IRQ_DOMAIN_HIERARCHY is not selected.
> 
> Signed-off-by: Jon Hunter <jonathanh@...dia.com>

Reviewed-by: Marc Zyngier <marc.zyngier@....com>

As discussed just before the 4.7 merge window, this patch is going to
uncover quite a few broken configurations (the main one being the PPI
triggers for the ARM architected timer, which seems to be wrong on a lot
of different platforms).

I'm proposing to put this patch[1] in the same queue in order to
uncover the guilty ones, but we have to be prepared for more breakage
(I've also identified kvmtool as a sinner).

Thanks,

	M.
[1] https://lkml.org/lkml/2016/5/9/546
-- 
Jazz is not dead. It just smells funny.