linux-kernel - Re: [RFC PATCH v3 06/11] dt-bindings: timer: Update SiFive CLINT bindings for IPI support

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Message-ID: <YS7Xk/Np2yc1/wrb@robh.at.kernel.org>
Date:   Tue, 31 Aug 2021 20:29:55 -0500
From:   Rob Herring <robh@...nel.org>
To:     Anup Patel <anup.patel@....com>
Cc:     Palmer Dabbelt <palmer@...belt.com>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Atish Patra <atish.patra@....com>,
        Alistair Francis <Alistair.Francis@....com>,
        Anup Patel <anup@...infault.org>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [RFC PATCH v3 06/11] dt-bindings: timer: Update SiFive CLINT
 bindings for IPI support

On Mon, Aug 30, 2021 at 09:47:24AM +0530, Anup Patel wrote:
> The Linux RISC-V now treats IPIs as regular per-CPU IRQs. This means
> we have to create a IPI interrupt domain to use CLINT IPI functionality
> hence requiring a "interrupt-controller" and "#interrupt-cells" DT
> property in CLINT DT nodes.
> 
> Impact of this CLINT DT bindings change only affects Linux RISC-V
> NoMMU kernel and has no effect of existing M-mode runtime firmwares
> (i.e. OpenSBI).

It appears to me you should fix Linux to not need these 2 useless 
properties. I say useless because #interrupt-cells being 0 is pretty 
useless.

> 
> Signed-off-by: Anup Patel <anup.patel@....com>
> ---
>  .../bindings/timer/sifive,clint.yaml          | 20 ++++++++++++++-----
>  arch/riscv/boot/dts/canaan/k210.dtsi          |  2 ++
>  .../boot/dts/microchip/microchip-mpfs.dtsi    |  2 ++
>  3 files changed, 19 insertions(+), 5 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/timer/sifive,clint.yaml b/Documentation/devicetree/bindings/timer/sifive,clint.yaml
> index a35952f48742..9c8ef9f4094f 100644
> --- a/Documentation/devicetree/bindings/timer/sifive,clint.yaml
> +++ b/Documentation/devicetree/bindings/timer/sifive,clint.yaml
> @@ -43,6 +43,12 @@ properties:
>  
>    interrupts-extended:
>      minItems: 1
> +    maxItems: 4095
> +
> +  "#interrupt-cells":
> +    const: 0
> +
> +  interrupt-controller: true
>  
>  additionalProperties: false
>  
> @@ -50,15 +56,19 @@ required:
>    - compatible
>    - reg
>    - interrupts-extended
> +  - interrupt-controller
> +  - "#interrupt-cells"
>  
>  examples:
>    - |
>      timer@...0000 {
>        compatible = "sifive,fu540-c000-clint", "sifive,clint0";
> -      interrupts-extended = <&cpu1intc 3 &cpu1intc 7
> -                             &cpu2intc 3 &cpu2intc 7
> -                             &cpu3intc 3 &cpu3intc 7
> -                             &cpu4intc 3 &cpu4intc 7>;
> -       reg = <0x2000000 0x10000>;
> +      interrupts-extended = <&cpu1intc 3>, <&cpu1intc 7>,
> +                            <&cpu2intc 3>, <&cpu2intc 7>,
> +                            <&cpu3intc 3>, <&cpu3intc 7>,
> +                            <&cpu4intc 3>, <&cpu4intc 7>;
> +      reg = <0x2000000 0x10000>;
> +      interrupt-controller;
> +      #interrupt-cells = <0>;
>      };
>  ...
> diff --git a/arch/riscv/boot/dts/canaan/k210.dtsi b/arch/riscv/boot/dts/canaan/k210.dtsi
> index 5e8ca8142482..67dcda1efadb 100644
> --- a/arch/riscv/boot/dts/canaan/k210.dtsi
> +++ b/arch/riscv/boot/dts/canaan/k210.dtsi
> @@ -105,6 +105,8 @@ clint0: timer@...0000 {
>  			reg = <0x2000000 0xC000>;
>  			interrupts-extended = <&cpu0_intc 3 &cpu0_intc 7
>  					      &cpu1_intc 3 &cpu1_intc 7>;
> +			#interrupt-cells = <0>;
> +			interrupt-controller;
>  		};
>  
>  		plic0: interrupt-controller@...0000 {
> diff --git a/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi b/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> index b9819570a7d1..67fb41439f20 100644
> --- a/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> +++ b/arch/riscv/boot/dts/microchip/microchip-mpfs.dtsi
> @@ -168,6 +168,8 @@ &cpu1_intc 3 &cpu1_intc 7
>  						&cpu2_intc 3 &cpu2_intc 7
>  						&cpu3_intc 3 &cpu3_intc 7
>  						&cpu4_intc 3 &cpu4_intc 7>;
> +			#interrupt-cells = <0>;
> +			interrupt-controller;
>  		};
>  
>  		plic: interrupt-controller@...0000 {
> -- 
> 2.25.1
> 
>