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

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Message-ID: <CAA8EJpqiN6oRMWhAMMP6EsAeki5KSMbO+XzEtT9YRdJKc9_Gbg@mail.gmail.com>
Date: Mon, 19 Feb 2024 18:21:06 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Marc Zyngier <maz@...nel.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 at 17:53, Marc Zyngier <maz@...nel.org> wrote:
>
> 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);

This works. But I wonder if the following change is even better. WDYT?

diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index aeb41655d6de..2f0d2700709e 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -449,14 +449,17 @@ 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 (fwnode != NULL &&
+                   h->fwnode == fwnode &&
+                   bus_token == DOMAIN_BUS_ANY)
+                       rc = true;
+               else if (h->ops->select)
                        rc = h->ops->select(h, fwspec, bus_token);
                else if (h->ops->match)
                        rc = h->ops->match(h, to_of_node(fwnode), bus_token);
                else
                        rc = ((fwnode != NULL) && (h->fwnode == fwnode) &&
-                             ((bus_token == DOMAIN_BUS_ANY) ||
-                              (h->bus_token == bus_token)));
+                             (h->bus_token == bus_token));

                if (rc) {
                        found = h;


-- 
With best wishes
Dmitry