linux-kernel - Re: [PATCH] of/irq: Add a quirk for controllers with their own definition of interrupt-map

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Date:   Mon, 29 Nov 2021 13:15:27 -0600
From:   Rob Herring <robh@...nel.org>
To:     Marc Zyngier <maz@...nel.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        devicetree@...r.kernel.org,
        Android Kernel Team <kernel-team@...roid.com>,
        John Crispin <john@...ozen.org>, Biwen Li <biwen.li@....com>,
        Chris Brandt <chris.brandt@...esas.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>
Subject: Re: [PATCH] of/irq: Add a quirk for controllers with their own
 definition of interrupt-map

On Mon, Nov 22, 2021 at 4:30 AM Marc Zyngier <maz@...nel.org> wrote:
>
> Since 041284181226 ("of/irq: Allow matching of an interrupt-map local
> to an interrupt controller"), a handful of interrupt controllers have
> stopped working correctly. This is due to the DT exposing a non-sensical
> interrupt-map property, and their drivers relying on the kernel ignoring
> this property.
>
> Since we cannot realistically fix this terrible behaviour, add a quirk
> for the limited set of devices that have implemented this monster,
> and document that this is a pretty bad practice.
>
> Cc: Rob Herring <robh@...nel.org>
> Cc: John Crispin <john@...ozen.org>
> Cc: Biwen Li <biwen.li@....com>
> Cc: Chris Brandt <chris.brandt@...esas.com>
> Cc: Geert Uytterhoeven <geert+renesas@...der.be>
> Signed-off-by: Marc Zyngier <maz@...nel.org>
> ---
>  drivers/of/irq.c | 37 +++++++++++++++++++++++++++++++++++--
>  1 file changed, 35 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/of/irq.c b/drivers/of/irq.c
> index b10f015b2e37..27a5173c813c 100644
> --- a/drivers/of/irq.c
> +++ b/drivers/of/irq.c
> @@ -76,6 +76,36 @@ struct device_node *of_irq_find_parent(struct device_node *child)
>  }
>  EXPORT_SYMBOL_GPL(of_irq_find_parent);
>
> +/*
> + * These interrupt controllers abuse interrupt-map for unspeakable
> + * reasons and rely on the core code to *ignore* it (the drivers do
> + * their own parsing of the property).
> + *
> + * If you think of adding to the list for something *new*, think
> + * again. There is a high chance that you will be sent back to the
> + * drawing board.
> + */
> +static const char * const of_irq_imap_abusers[] = {
> +       "CBEA,platform-spider-pic",
> +       "sti,platform-spider-pic",
> +       "realtek,rtl-intc",
> +       "fsl,ls1021a-extirq",
> +       "fsl,ls1043a-extirq",
> +       "fsl,ls1088a-extirq",
> +       "renesas,rza1-irqc",
> +};

I guess this list was obtained by with a: git grep '"interrupt-map"'

I suppose that should be sufficient to find all the cases. I'd like to
be able to identify this case just from a DT file, but it's not really
clear

Perhaps a simpler solution to all this is only handle interrupt-map
with interrupt-controller if it points to its own node. That works for
Apple and I don't see a need beyond that case.


> +static bool of_irq_abuses_interrupt_map(struct device_node *np)
> +{
> +       int i;
> +
> +       for (i = 0; i < ARRAY_SIZE(of_irq_imap_abusers); i++)
> +               if (of_device_is_compatible(np, of_irq_imap_abusers[i]))
> +                       return true;
> +
> +       return false;

With a NULL terminated list, you can use of_device_compatible_match() instead .

Rob