linux-kernel - Re: [PATCH v2 14/15] ARM: dts: bcm2711: Add the BSC interrupt controller

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Message-ID: <20210210144043.s4plyc7ekwnnu7k4@gilmour>
Date:   Wed, 10 Feb 2021 15:40:43 +0100
From:   Maxime Ripard <maxime@...no.tech>
To:     Dave Stevenson <dave.stevenson@...pberrypi.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>
Cc:     Eric Anholt <eric@...olt.net>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Daniel Vetter <daniel.vetter@...el.com>,
        David Airlie <airlied@...ux.ie>,
        linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        LKML <linux-kernel@...r.kernel.org>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        bcm-kernel-feedback-list@...adcom.com,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
Subject: Re: [PATCH v2 14/15] ARM: dts: bcm2711: Add the BSC interrupt
 controller

Hi Dave,

On Tue, Feb 09, 2021 at 09:49:05AM +0000, Dave Stevenson wrote:
> On Mon, 11 Jan 2021 at 14:23, Maxime Ripard <maxime@...no.tech> wrote:
> >
> > The BSC controllers used for the HDMI DDC have an interrupt controller
> > shared between both instances. Let's add it to avoid polling.
> 
> This seems to have unintended side effects.
> GIC interrupt 117 is shared between the standard I2C controllers
> (i2c-bcm2835) and the l2-intc block handling the HDMI I2C interrupts.
> 
> Whilst i2c-bcm2835 requests the interrupt with IRQF_SHARED, that
> doesn't appear to be an option for l2-intc registering as an interrupt
> controller. i2c-bcm2835 therefore loses out and fails to register for
> the interrupt.
> 
> Is there an equivalent flag that an interrupt controller can add to
> say that the parent interrupt is shared? Is that even supported?

Indeed, it looks like setting an equivalent to IRQF_SHARED would be the
solution, but I couldn't find anything that would allow us to in the
irqchip code.

Marc, Thomas, is it something that is allowed?

Thanks!
Maxime

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