linux-kernel - Re: [PATCH V2 04/14] irqdomain: Fix handling of type settings for existing mappings

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Date:	Fri, 22 Apr 2016 09:11:58 +0100
From:	Marc Zyngier <marc.zyngier@....com>
To:	Jon Hunter <jonathanh@...dia.com>,
	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>
Cc:	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, linux-omap@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 04/14] irqdomain: Fix handling of type settings for
 existing mappings

On 20/04/16 12:03, Jon Hunter wrote:
> When mapping an IRQ, it is possible that a mapping for the IRQ already
> exists. If mapping does exist then there are the following issues with
> regard to the handling of the IRQ type settings ...
> 1. If the domain is part of a hierarchy, then:
>    a. We do not check that the type settings for the existing mapping
>       match those of the new mapping.
>    b. We do not check to see if the type settings have been programmed
>       yet (and they might not have been) and so we may never set the
>       type.
> 2. If the domain is NOT part of a hierarchy, we will overwrite the
>    current type settings programmed if they are different from the
>    previous mapping. Please note that irq_create_mapping()
>    calls irq_find_mapping() to check if a mapping already exists.
> 
> Although, it may be unlikely that the type settings for a shared
> interrupt would not match, nonetheless we should check for this.
> Therefore, to fix this check if a mapping exists (regardless of whether
> the domain is part of a hierarchy or not) and if it does then:
> 1. Return the IRQ number if the type settings match or are not
>    specified.
> 2. Program the type settings and return the IRQ number if the type
>    settings have not been programmed yet.
> 3. Otherwise if the type setting do not match, then print a warning
>    and don't return the IRQ number.
> 
> Furthermore, add a warning if the type return by irq_domain_translate()
> has bits outside the sense mask set and then clear these bits. If these
> bits are not cleared then this will cause the comparision of the type
> settings for an existing mapping to fail with that of the new mapping
> even if the sense bit themselves match. The reason being is that the
> existing type settings are read by calling irq_get_trigger_type() which
> will clear any bits outside the sense mask. This will allow us to detect
> irqchips that are not correctly clearing these bits and fix them.
> 
> Signed-off-by: Jon Hunter <jonathanh@...dia.com>

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

	M.
-- 
Jazz is not dead. It just smells funny...