linux-kernel - Re: [PATCH] irqchip/gic-v3: handle DOMAIN_BUS_ANY in gic_irq_domain

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Message-ID: <868r3g4fhv.wl-maz@kernel.org>
Date: Mon, 19 Feb 2024 15:53:48 +0000
From: Marc Zyngier <maz@...nel.org>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Thomas Gleixner <tglx@...utronix.de>,
	Anup Patel <apatel@...tanamicro.com>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH] irqchip/gic-v3: handle DOMAIN_BUS_ANY in gic_irq_domain_select

On Mon, 19 Feb 2024 14:47:37 +0000,
Dmitry Baryshkov <dmitry.baryshkov@...aro.org> wrote:
> 
> Before the commit de1ff306dcf4 ("genirq/irqdomain: Remove the param
> count restriction from select()") the irq_find_matching_fwspec() was
> handling the DOMAIN_BUS_ANY on its own. After this commit it is a job of
> the select() callback. However the callback of GICv3 (even though it got
> modified to handle zero param_count) wasn't prepared to return true for
> DOMAIN_BUS_ANY bus_token.
> 
> This breaks probing of any of the child IRQ domains, since
> platform_irqchip_probe() uses irq_find_matching_host(par_np,
> DOMAIN_BUS_ANY) to check for the presence of the parent IRQ domain.
> 
> Fixes: 151378251004 ("irqchip/gic-v3: Make gic_irq_domain_select() robust for zero parameter count")
> Fixes: de1ff306dcf4 ("genirq/irqdomain: Remove the param count restriction from select()")
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> ---
>  drivers/irqchip/irq-gic-v3.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
> index 6fb276504bcc..e9e9643c653f 100644
> --- a/drivers/irqchip/irq-gic-v3.c
> +++ b/drivers/irqchip/irq-gic-v3.c
> @@ -1696,7 +1696,8 @@ static int gic_irq_domain_select(struct irq_domain *d,
>  
>  	/* Handle pure domain searches */
>  	if (!fwspec->param_count)
> -		return d->bus_token == bus_token;
> +		return d->bus_token == bus_token ||
> +			bus_token == DOMAIN_BUS_ANY;
>  
>  	/* If this is not DT, then we have a single domain */
>  	if (!is_of_node(fwspec->fwnode))
> 

I really dislike the look of this. If that's the case, any irqchip
that has a 'select' method (such as imx-intmux) should be similarly
hacked. And at this point, this should be handled by the core code.

Can you try this instead? I don't have any HW that relies on
behaviour, but I'd expect this to work.

Thanks,

	M.

diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index aeb41655d6de..3dd1c871e091 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -449,7 +449,7 @@ struct irq_domain *irq_find_matching_fwspec(struct irq_fwspec *fwspec,
 	 */
 	mutex_lock(&irq_domain_mutex);
 	list_for_each_entry(h, &irq_domain_list, link) {
-		if (h->ops->select)
+		if (h->ops->select && bus_token != DOMAIN_BUS_ANY)
 			rc = h->ops->select(h, fwspec, bus_token);
 		else if (h->ops->match)
 			rc = h->ops->match(h, to_of_node(fwnode), bus_token);

-- 
Without deviation from the norm, progress is not possible.