Re: [PATCH V4 2/3] dt-bindings: update riscv plic compatible string

[Heiko Stuebner <heiko@sntech.de>]

Hi Guo,

Am Samstag, 16. Oktober 2021, 05:21:59 CEST schrieb guoren@kernel.org:
> From: Guo Ren <guoren@linux.alibaba.com>
> 
> Add the compatible string "thead,c900-plic" to the riscv plic
> bindings to support allwinner d1 SOC which contains c906 core.

The compatible strings sound good now, but some things below

> 
> Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> Cc: Rob Herring <robh@kernel.org>
> Cc: Palmer Dabbelt <palmerdabbelt@google.com>
> Cc: Anup Patel <anup@brainfault.org>
> Cc: Atish Patra <atish.patra@wdc.com>
> 
> ---
> 
> Changes since V4:
>  - Update description in errata style
>  - Update enum suggested by Anup, Heiko, Samuel
> 
> Changes since V3:
>  - Rename "c9xx" to "c900"
>  - Add thead,c900-plic in the description section
> ---
>  .../interrupt-controller/sifive,plic-1.0.0.yaml       | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/devicetree/bindings/interrupt-controller/sifive,plic-1.0.0.yaml b/Documentation/devicetree/bindings/interrupt-controller/sifive,plic-1.0.0.yaml
> index 08d5a57ce00f..272f29540135 100644
> --- a/Documentation/devicetree/bindings/interrupt-controller/sifive,plic-1.0.0.yaml
> +++ b/Documentation/devicetree/bindings/interrupt-controller/sifive,plic-1.0.0.yaml
> @@ -35,6 +35,12 @@ description:
>    contains a specific memory layout, which is documented in chapter 8 of the
>    SiFive U5 Coreplex Series Manual <https://static.dev.sifive.com/U54-MC-RVCoreIP.pdf>.
>  
> +  The C9xx PLIC does not comply with the interrupt claim/completion process defined
> +  by the RISC-V PLIC specification because C9xx PLIC will mask an IRQ when it is
> +  claimed by PLIC driver (i.e. readl(claim) and the IRQ will be unmasked upon
> +  completion by PLIC driver (i.e. writel(claim). This behaviour breaks the handling
> +  of IRQS_ONESHOT by the generic handle_fasteoi_irq() used in the PLIC driver.
> +
>  maintainers:
>    - Sagar Kadam <sagar.kadam@sifive.com>
>    - Paul Walmsley  <paul.walmsley@sifive.com>
> @@ -46,7 +52,10 @@ properties:
>        - enum:
>            - sifive,fu540-c000-plic
>            - canaan,k210-plic
> -      - const: sifive,plic-1.0.0
> +      - enmu:

	^ spelling enum

> +          - sifive,plic-1.0.0
> +          - thead,c900-plic
> +          - allwinner,sun20i-d1-plic

but in general I'd think that you want something like

  compatible:
    oneOf:
      - items:
          - enum:
              - sifive,fu540-c000-plic
              - canaan,k210-plic
          - const: sifive,plic-1.0.0
      - items:
          - enum:
              - allwinner,sun20i-d1-plic
          - const: thead,c900-plic

Having only one item list would allow as valid combinations like
"sifive,fu540-c000-plic", "thead,c900-plic" when checking the schema.

With the oneOf and separate lists we can make sure that such
"illegal" combinations get flagged by the dtbs_check

[the enum with the single allwinner entry already leaves
 room for later addition to the c900-plic variant]

Heiko