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From:   "Lad, Prabhakar" <prabhakar.csengg@gmail.com>
Date:   Thu, 16 Dec 2021 17:36:59 +0000
Message-ID: <CA+V-a8uRtzNuibBnnWi-OKx0dSaK=f0Ddb_fFXjj_F55bNGzKw@mail.gmail.com>
Subject: Re: [PATCH] irqchip/renesas-intc-irqpin: Use platform_get_irq_optional()
 to get the interrupt
To:     Geert Uytterhoeven <geert@linux-m68k.org>
Cc:     Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Marc Zyngier <maz@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux-Renesas <linux-renesas-soc@vger.kernel.org>
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Precedence: bulk

Hi Geert,

On Thu, Dec 16, 2021 at 2:31 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>
> Hi Prabhakar,
>
> On Thu, Dec 16, 2021 at 3:23 PM Lad, Prabhakar
> <prabhakar.csengg@gmail.com> wrote:
> > On Thu, Dec 16, 2021 at 8:45 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > > On Thu, Dec 16, 2021 at 12:45 AM Lad Prabhakar
> > > <prabhakar.mahadev-lad.rj@bp.renesas.com> wrote:
> > > > platform_get_resource(pdev, IORESOURCE_IRQ, ..) relies on static
> > > > allocation of IRQ resources in DT core code, this causes an issue
> > > > when using hierarchical interrupt domains using "interrupts" property
> > > > in the node as this bypassed the hierarchical setup and messed up the
> > > > irq chaining.
> > > >
> > > > In preparation for removal of static setup of IRQ resource from DT core
> > > > code use platform_get_irq_optional().
> > > >
> > > > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> > >
> > > > --- a/drivers/irqchip/irq-renesas-intc-irqpin.c
> > > > +++ b/drivers/irqchip/irq-renesas-intc-irqpin.c
> > >
> > > > @@ -418,12 +417,14 @@ static int intc_irqpin_probe(struct platform_device *pdev)
> > > >
> > > >         /* allow any number of IRQs between 1 and INTC_IRQPIN_MAX */
> > > >         for (k = 0; k < INTC_IRQPIN_MAX; k++) {
> > > > -               irq = platform_get_resource(pdev, IORESOURCE_IRQ, k);
> > > > -               if (!irq)
> > > > +               ret = platform_get_irq_optional(pdev, k);
> > > > +               if (ret == -EPROBE_DEFER)
> > > > +                       goto err0;
> > > > +               if (ret < 0)
> > > >                         break;
> > >
> > > Shouldn't all errors be considered fatal, except for -ENXIO (no
> > > interrupt)?
> > >
> > Initial behavior of this driver was even if one
> > platform_get_resource() succeeded the probe continued further, this is
>
> Indeed, the loop obtained all interrupts present, until no more are to found.
> In the old logic, it would return a NULL resource for the first
> non-existing one.
> In the new logic, it would return -ENXIO.
> Hence you need to check for -ENXIO in the loop, to distinguish "no more
> interrupts" from actual errors.
>
Thanks for the clarification, I'll post a v2 with the changes.

> > the same behavior which I wanted to keep with this code while using
> > platform_get_irq_optional(). But as you pointed out I'll change it to below:
> >
> > +               ret = platform_get_irq(pdev, k);
> > +               if (ret < 0)
> > +                       goto err0;
> >
> > We bail out any error case and will also drop the check for (nirqs < 1).
>
> I think that check should stay: there should be at least one interrupt.
>
Agreed.

Cheers,
Prabhakar
> > > >                 p->irq[k].p = p;
> > > > -               p->irq[k].requested_irq = irq->start;
> > > > +               p->irq[k].requested_irq = ret;
> > > >         }
> > > >
> > > >         nirqs = k;
>
> Gr{oetje,eeting}s,
>
>                         Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds