linux-kernel - Re: Similar SoCs with different CPUs and interrupt bindings

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Message-ID: <567e9e6c-e34c-4ded-9622-9ad8387dd24b@arm.com>
Date:   Wed, 21 Sep 2022 11:14:10 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        "Lad, Prabhakar" <prabhakar.csengg@...il.com>
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Andre Przywara <andre.przywara@....com>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Samuel Holland <samuel@...lland.org>,
        Biju Das <biju.das.jz@...renesas.com>,
        Chris Paterson <Chris.Paterson2@...esas.com>,
        Atish Patra <atishp@...shpatra.org>,
        "Lad, Prabhakar" <prabhakar.mahadev-lad.rj@...renesas.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>
Subject: Re: Similar SoCs with different CPUs and interrupt bindings

On 2022-09-21 10:26, Krzysztof Kozlowski wrote:
> On 21/09/2022 11:20, Lad, Prabhakar wrote:
>>>
>>> What do you mean? Macros support string concatenation and simple
>>> arithmetic like adding numbers. I just tested it.
>>>
>> I did try the below:
>>
>> diff --git a/arch/arm64/boot/dts/renesas/r9a07g043.dtsi
>> b/arch/arm64/boot/dts/renesas/r9a07g043.dtsi
>> index 689aa4ba416b..0f923c276cd3 100644
>> --- a/arch/arm64/boot/dts/renesas/r9a07g043.dtsi
>> +++ b/arch/arm64/boot/dts/renesas/r9a07g043.dtsi
>> @@ -8,6 +8,8 @@
>>   #include <dt-bindings/interrupt-controller/arm-gic.h>
>>   #include <dt-bindings/clock/r9a07g043-cpg.h>
>>
>> +#define SOC_PERIPHERAL_IRQ(nr, na) GIC_SPI nr na
>> +
>>   / {
>>       compatible = "renesas,r9a07g043";
>>       #address-cells = <2>;
>> @@ -128,7 +130,7 @@ ssi1: ssi@...4a000 {
>>               compatible = "renesas,r9a07g043-ssi",
>>                        "renesas,rz-ssi";
>>               reg = <0 0x1004a000 0 0x400>;
>> -            interrupts = <GIC_SPI 330 IRQ_TYPE_LEVEL_HIGH>,
>> +            interrupts = <SOC_PERIPHERAL_IRQ(330, IRQ_TYPE_LEVEL_HIGH)>,
>>                        <GIC_SPI 331 IRQ_TYPE_EDGE_RISING>,
>>                        <GIC_SPI 332 IRQ_TYPE_EDGE_RISING>,
>>                        <GIC_SPI 333 IRQ_TYPE_EDGE_RISING>;
>>
>> This worked as expected, but couldn't get the arithmetic operation
>> working. Could you please provide an example?
> 
> diff --git a/arch/arm64/boot/dts/renesas/r9a07g043.dtsi b/arch/arm64/boot/dts/renesas/r9a07g043.dtsi
> index ff6aab388eb7..0ecca775fa3f 100644
> --- a/arch/arm64/boot/dts/renesas/r9a07g043.dtsi
> +++ b/arch/arm64/boot/dts/renesas/r9a07g043.dtsi
> @@ -8,6 +8,8 @@
>   #include <dt-bindings/interrupt-controller/arm-gic.h>
>   #include <dt-bindings/clock/r9a07g043-cpg.h>
>   
> +#define SOC_PERIPHERAL_IRQ_NUMBER(na)  (na + 32)
> +#define SOC_PERIPHERAL_IRQ(nr, na) GIC_SPI nr SOC_PERIPHERAL_IRQ_NUMBER(na)
>   / {
>          compatible = "renesas,r9a07g043";
>          #address-cells = <2>;
> @@ -128,7 +130,7 @@ ssi1: ssi@...4a000 {
>                          compatible = "renesas,r9a07g043-ssi",
>                                       "renesas,rz-ssi";
>                          reg = <0 0x1004a000 0 0x400>;
> -                       interrupts = <GIC_SPI 330 IRQ_TYPE_LEVEL_HIGH>,
> +                       interrupts = <SOC_PERIPHERAL_IRQ(330, IRQ_TYPE_LEVEL_HIGH)>,
> 
> 
> 
> Or any other method like that....

Which will generate the text:

	"interrupts = <GIC_SPI 330 (IRQ_TYPE_LEVEL_HIGH + 32)>,"

(give or take some whitespace)

CPP supports constant expressions in #if and #elif directives, but 
macros are purely literal text replacement. It might technically be 
achievable with some insane CPP metaprogramming, but for all practical 
purposes this is a non-starter unless dtc itself grows the ability to 
process arithmetic expressions.

Thanks,
Robin.