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Message-ID: <9be58cb4-4ee8-a6e0-7a0a-f2f581e394d3@linaro.org>
Date:   Mon, 14 Nov 2022 10:49:24 +0100
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Subject: Re: [PATCH 4/9] dt-bindings: Add RISC-V incoming MSI controller
 bindings
Content-Language: en-US
To:     Anup Patel <apatel@ventanamicro.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Marc Zyngier <maz@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>
Cc:     Atish Patra <atishp@atishpatra.org>,
        Alistair Francis <Alistair.Francis@wdc.com>,
        Anup Patel <anup@brainfault.org>,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        devicetree@vger.kernel.org
References: <20221111044207.1478350-1-apatel@ventanamicro.com>
 <20221111044207.1478350-5-apatel@ventanamicro.com>
From:   Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
In-Reply-To: <20221111044207.1478350-5-apatel@ventanamicro.com>
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Precedence: bulk

On 11/11/2022 05:42, Anup Patel wrote:
> We add DT bindings document for RISC-V incoming MSI controller (IMSIC)
> defined by the RISC-V advanced interrupt architecture (AIA) specification.
> 
> Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> ---
>  .../interrupt-controller/riscv,imsic.yaml     | 174 ++++++++++++++++++
>  1 file changed, 174 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/interrupt-controller/riscv,imsic.yaml
> 
> diff --git a/Documentation/devicetree/bindings/interrupt-controller/riscv,imsic.yaml b/Documentation/devicetree/bindings/interrupt-controller/riscv,imsic.yaml
> new file mode 100644
> index 000000000000..05106eb1955e
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/interrupt-controller/riscv,imsic.yaml
> @@ -0,0 +1,174 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/interrupt-controller/riscv,imsic.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: RISC-V Incoming MSI Controller (IMSIC)
> +
> +maintainers:
> +  - Anup Patel <anup@brainfault.org>
> +
> +description:
> +  The RISC-V advanced interrupt architecture (AIA) defines a per-CPU incoming
> +  MSI controller (IMSIC) for handling MSIs in a RISC-V platform. The RISC-V
> +  AIA specification can be found at https://github.com/riscv/riscv-aia.
> +
> +  The IMSIC is a per-CPU (or per-HART) device with separate interrupt file
> +  for each privilege level (machine or supervisor). The configuration of
> +  a IMSIC interrupt file is done using AIA CSRs and it also has a 4KB MMIO
> +  space to receive MSIs from devices. Each IMSIC interrupt file supports a
> +  fixed number of interrupt identities (to distinguish MSIs from devices)
> +  which is same for given privilege level across CPUs (or HARTs).
> +
> +  The arrangement of IMSIC interrupt files in MMIO space of a RISC-V platform
> +  follows a particular scheme defined by the RISC-V AIA specification. A IMSIC
> +  group is a set of IMSIC interrupt files co-located in MMIO space and we can
> +  have multiple IMSIC groups (i.e. clusters, sockets, chiplets, etc) in a
> +  RISC-V platform. The MSI target address of a IMSIC interrupt file at given
> +  privilege level (machine or supervisor) encodes group index, HART index,
> +  and guest index (shown below).
> +
> +  XLEN-1           >=24                                 12    0
> +  |                  |                                  |     |
> +  -------------------------------------------------------------
> +  |xxxxxx|Group Index|xxxxxxxxxxx|HART Index|Guest Index|  0  |
> +  -------------------------------------------------------------
> +
> +  The device tree of a RISC-V platform will have one IMSIC device tree node
> +  for each privilege level (machine or supervisor) which collectively describe
> +  IMSIC interrupt files at that privilege level across CPUs (or HARTs).
> +
> +allOf:
> +  - $ref: /schemas/interrupt-controller.yaml#
> +
> +properties:
> +  compatible:
> +    items:
> +      - enum:
> +          - vendor,chip-imsics

There is no such vendor... As Conor pointed out, this does not look
correct. Compatibles must be real and specific.

> +      - const: riscv,imsics
> +
> +  reg:
> +    minItems: 1
> +    maxItems: 128

Is there a DTS with 128 reg items?

> +    description:
> +      Base address of each IMSIC group.
> +
> +  interrupt-controller: true
> +
> +  "#interrupt-cells":
> +    const: 0
> +
> +  msi-controller: true

You want then msi-controller.yaml schema and you can drop properties
described there.

> +
> +  interrupts-extended:
> +    minItems: 1
> +    maxItems: 32768

I just wonder if you are not putting some random stuff here... just like
this "vendor" company.

32768 inputs it is quite a big chip. Are you sure you have so many pins
or internal connections?

> +    description:
> +      This property represents the set of CPUs (or HARTs) for which given
> +      device tree node describes the IMSIC interrupt files. Each node pointed
> +      to should be a riscv,cpu-intc node, which has a riscv node (i.e. RISC-V
> +      HART) as parent.
> +
> +  riscv,num-ids:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    minimum: 63
> +    maximum: 2047
> +    description:
> +      Specifies how many interrupt identities are supported by IMSIC interrupt
> +      file.
> +
> +  riscv,num-guest-ids:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    minimum: 63
> +    maximum: 2047
> +    description:
> +      Specifies how many interrupt identities are supported by IMSIC guest
> +      interrupt file. When not specified the number of interrupt identities
> +      supported by IMSIC guest file is assumed to be same as specified by
> +      the riscv,num-ids property.
> +
> +  riscv,slow-ipi:
> +    type: boolean
> +    description:
> +      The presence of this property implies that software interrupts (i.e.
> +      IPIs) using IMSIC software injected MSIs is slower compared to other
> +      software interrupt mechanisms (such as SBI IPI) on the underlying
> +      RISC-V platform.

Is this a property of software or hardware?

> +
> +  riscv,guest-index-bits:
> +    minimum: 0
> +    maximum: 7
> +    description:
> +      Specifies number of guest index bits in the MSI target address. When
> +      not specified it is assumed to be 0.
> +
> +  riscv,hart-index-bits:
> +    minimum: 0
> +    maximum: 15
> +    description:
> +      Specifies number of HART index bits in the MSI target address. When
> +      not specified it is estimated based on the interrupts-extended property.
> +
> +  riscv,group-index-bits:
> +    minimum: 0
> +    maximum: 7
> +    description:
> +      Specifies number of group index bits in the MSI target address. When
> +      not specified it is assumed to be 0.

Then default: 0.

> +
> +  riscv,group-index-shift:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    minimum: 24
> +    maximum: 55
> +    description:
> +      Specifies the least significant bit of the group index bits in the

Please drop everywhere "Specifies the" and instead just describe the
hardware.

> +      MSI target address. When not specified it is assumed to be 24.
> +
> +additionalProperties: false

unevaluatedProperties: false and drop all properties already described
by other schemas.

> +
> +required:
> +  - compatible
> +  - reg
> +  - interrupt-controller
> +  - msi-controller
> +  - interrupts-extended
> +  - riscv,num-ids
> +
> +examples:
> +  - |
> +    // Example 1 (Machine-level IMSIC files with just one group):
> +
> +    imsic_mlevel: interrupt-controller@24000000 {
> +      compatible = "vendor,chip-imsics", "riscv,imsics";
> +      interrupts-extended = <&cpu1_intc 11>,
> +                            <&cpu2_intc 11>,
> +                            <&cpu3_intc 11>,
> +                            <&cpu4_intc 11>;
> +      reg = <0x28000000 0x4000>;
> +      interrupt-controller;
> +      #interrupt-cells = <0>;
> +      msi-controller;
> +      riscv,num-ids = <127>;
> +    };
> +
> +  - |
> +    // Example 2 (Supervisor-level IMSIC files with two groups):
> +
> +    imsic_slevel: interrupt-controller@28000000 {
> +      compatible = "vendor,chip-imsics", "riscv,imsics";

Please run scripts/checkpatch.pl and fix reported warnings.

Best regards,
Krzysztof