linux-kernel - Re: [RFC PATCH] of: platform: Skip mapping of interrupts in of_device

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Date:   Wed, 8 Dec 2021 21:08:00 -0600
From:   Rob Herring <robh+dt@...nel.org>
To:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Cc:     Frank Rowand <frowand.list@...il.com>,
        Marc Zyngier <maz@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "open list:MEDIA DRIVERS FOR RENESAS - FCP" 
        <linux-renesas-soc@...r.kernel.org>,
        Prabhakar <prabhakar.csengg@...il.com>,
        Biju Das <biju.das.jz@...renesas.com>
Subject: Re: [RFC PATCH] of: platform: Skip mapping of interrupts in of_device_alloc()

On Wed, Dec 8, 2021 at 6:11 PM Lad Prabhakar
<prabhakar.mahadev-lad.rj@...renesas.com> wrote:
>
> of_device_alloc() in early boot stage creates a interrupt mapping if
> there exists a "interrupts" property in the node.
>
> For hierarchical interrupt domains using "interrupts" property in the node
> bypassed the hierarchical setup and messed up the irq setup.
>
> This patch adds a check in of_device_alloc() to skip interrupt mapping if
> "not-interrupt-producer" property is present in the node. This allows
> nodes to describe the interrupts using "interrupts" property.
>
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> ---
> Hi All,
>
> Spawning from discussion [1], here is simple patch (not the ideal probably
> welcome for suggestions) from stopping the OF code from creating a map for
> the interrupts when using "interrupts" property.
>
> [1] https://lore.kernel.org/lkml/87pmqrck2m.wl-maz@kernel.org/
>     T/#mbd1e47c1981082aded4b32a52e2c04291e515508
>
> Cheers,
> Prabhakar
> ---
>  drivers/of/platform.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> index b3faf89744aa..629776ca1721 100644
> --- a/drivers/of/platform.c
> +++ b/drivers/of/platform.c
> @@ -114,7 +114,7 @@ struct platform_device *of_device_alloc(struct device_node *np,
>                                   struct device *parent)
>  {
>         struct platform_device *dev;
> -       int rc, i, num_reg = 0, num_irq;
> +       int rc, i, num_reg = 0, num_irq = 0;
>         struct resource *res, temp_res;
>
>         dev = platform_device_alloc("", PLATFORM_DEVID_NONE);
> @@ -124,7 +124,14 @@ struct platform_device *of_device_alloc(struct device_node *np,
>         /* count the io and irq resources */
>         while (of_address_to_resource(np, num_reg, &temp_res) == 0)
>                 num_reg++;
> -       num_irq = of_irq_count(np);
> +
> +       /*
> +        * we don't want to map the interrupts of hierarchical interrupt domain
> +        * into the parent domain yet. This will be the job of the hierarchical
> +        * interrupt driver code to map the interrupts as and when needed.
> +        */
> +       if (!of_property_read_bool(np, "not-interrupt-producer"))
> +               num_irq = of_irq_count(np);

The property won't fly for sure. A compatible match table could work
here, but I don't really want another temporary solution.

>         /* Populate the resource table */
>         if (num_irq || num_reg) {
> @@ -140,7 +147,7 @@ struct platform_device *of_device_alloc(struct device_node *np,
>                         rc = of_address_to_resource(np, i, res);
>                         WARN_ON(rc);
>                 }
> -               if (of_irq_to_resource_table(np, res, num_irq) != num_irq)
> +               if (num_irq && of_irq_to_resource_table(np, res, num_irq) != num_irq)

You might want to look at commit 9ec36cafe43b ("of/irq: do irq
resolution in platform_get_irq"). The intent was to remove this code,
but looks like the cleanup has a ways to go 7 years on. Primarily,
it's convert any platform_get_resource(pdev, IORESOURCE_IRQ, n) call
to platform_get_irq(). There's ~169 of those.

There are probably some open coded accesses to pdev->resources too,
but I didn't spot any.

Rob