linux-kernel - Re: [PATCH] of/irq: Don't ignore interrupt-controller when interrupt-map failed

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Message-ID: <20211112150415.GA1401861@bhelgaas>
Date:   Fri, 12 Nov 2021 09:04:15 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Marc Zyngier <maz@...nel.org>
Cc:     linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        Christian Zigotzky <chzigotzky@...osoft.de>,
        Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH] of/irq: Don't ignore interrupt-controller when
 interrupt-map failed

On Fri, Nov 12, 2021 at 02:36:44PM +0000, Marc Zyngier wrote:
> Since 041284181226 ("of/irq: Allow matching of an interrupt-map local
> to an interrupt controller"), the irq code favors using an interrupt-map
> over a interrupt-controller property if both are available, while the
> earlier behaviour was to ignore the interrupt-map altogether.
> 
> However, we now end-up with the opposite behaviour, which is to
> ignore the interrupt-controller property even if the interrupt-map
> fails to match its input. This new behaviour breaks the AmigaOne
> X1000 machine, which ships with an extremely "creative" (read:
> broken) device tree.
> 
> Fix this by allowing the interrupt-controller property to be selected
> when interrupt-map fails to match anything.
> 
> Fixes: 041284181226 ("of/irq: Allow matching of an interrupt-map local to an interrupt controller")
> Reported-by: Christian Zigotzky <chzigotzky@...osoft.de>
> Signed-off-by: Marc Zyngier <maz@...nel.org>
> Link: https://lore.kernel.org/r/78308692-02e6-9544-4035-3171a8e1e6d4@xenosoft.de
> Cc: Rob Herring <robh@...nel.org>
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>

I'm not qualified to review this, but since 041284181226 was merged
via my tree along with the rest of the Apple stuff, let me know if
you'd like me to merge this.

I see Rob has a comment, so if you want to take care merging it
yourself, that's certainly fine with me.

> ---
>  drivers/of/irq.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/of/irq.c b/drivers/of/irq.c
> index 32be5a03951f..508fb1717de3 100644
> --- a/drivers/of/irq.c
> +++ b/drivers/of/irq.c
> @@ -161,9 +161,10 @@ int of_irq_parse_raw(const __be32 *addr, struct of_phandle_args *out_irq)
>  		 * if it is then we are done, unless there is an
>  		 * interrupt-map which takes precedence.
>  		 */
> +		bool intc = of_property_read_bool(ipar, "interrupt-controller");
> +
>  		imap = of_get_property(ipar, "interrupt-map", &imaplen);
> -		if (imap == NULL &&
> -		    of_property_read_bool(ipar, "interrupt-controller")) {
> +		if (imap == NULL && intc) {
>  			pr_debug(" -> got it !\n");
>  			return 0;
>  		}
> @@ -244,8 +245,14 @@ int of_irq_parse_raw(const __be32 *addr, struct of_phandle_args *out_irq)
>  
>  			pr_debug(" -> imaplen=%d\n", imaplen);
>  		}
> -		if (!match)
> +		if (!match) {
> +			if (intc) {
> +				pr_debug("%pOF interrupt-map failed, using interrupt-controller\n", ipar);
> +				return 0;
> +			}
> +
>  			goto fail;
> +		}
>  
>  		/*
>  		 * Successfully parsed an interrrupt-map translation; copy new
> -- 
> 2.30.2
>