linux-kernel - Re: [PATCH hyperv-next v4 4/6] dt-bindings: microsoft,vmbus: Add GIC and DMA coherence to the example

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Message-ID: <20250212-rough-terrier-of-serendipity-68a0db@krzk-bin>
Date: Wed, 12 Feb 2025 07:42:28 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Roman Kisel <romank@...ux.microsoft.com>
Cc: arnd@...db.de, bhelgaas@...gle.com, bp@...en8.de, 
	catalin.marinas@....com, conor+dt@...nel.org, dave.hansen@...ux.intel.com, 
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	tglx@...utronix.de, wei.liu@...nel.org, will@...nel.org, devicetree@...r.kernel.org, 
	linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
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	x86@...nel.org, benhill@...rosoft.com, bperkins@...rosoft.com, 
	sunilmut@...rosoft.com
Subject: Re: [PATCH hyperv-next v4 4/6] dt-bindings: microsoft,vmbus: Add GIC
 and DMA coherence to the example

On Tue, Feb 11, 2025 at 05:43:19PM -0800, Roman Kisel wrote:
> The existing example lacks the GIC interrupt controller property
> making it not possible to boot on ARM64, and it lacks the DMA

GIC controller is not relevant to this binding.

> coherence property making the kernel do more work on maintaining
> CPU caches on ARM64 although the VMBus trancations are cache-coherent.
> 
> Add the GIC node, specify DMA coherence, and define interrupt-parent
> and interrupts properties in the example to provide a complete reference
> for platforms utilizing GIC-based interrupts, and add the DMA coherence
> property to not do extra work on the architectures where DMA defaults to
> non cache-coherent.
> 
> Signed-off-by: Roman Kisel <romank@...ux.microsoft.com>
> ---
>  .../devicetree/bindings/bus/microsoft,vmbus.yaml      | 11 +++++++++++
>  1 file changed, 11 insertions(+)

Last time I said: not tested by automation.
Now: I see automation build failures, although I do not see anything
incorrect in the code, so that's a bit surprising. Please confirm that
binding was tested on latest dtschema.

> 
> diff --git a/Documentation/devicetree/bindings/bus/microsoft,vmbus.yaml b/Documentation/devicetree/bindings/bus/microsoft,vmbus.yaml
> index a8d40c766dcd..5ec69226ab85 100644
> --- a/Documentation/devicetree/bindings/bus/microsoft,vmbus.yaml
> +++ b/Documentation/devicetree/bindings/bus/microsoft,vmbus.yaml
> @@ -44,11 +44,22 @@ examples:
>              #size-cells = <1>;
>              ranges;
>  
> +            gic: intc@...00000 {
> +              compatible = "arm,gic-v3";
> +              reg = <0x0 0xfe200000 0x0 0x10000>,   /* GIC Dist */
> +                    <0x0 0xfe280000 0x0 0x200000>;  /* GICR */
> +              interrupt-controller;
> +              #interrupt-cells = <3>;
> +            }

I fail to see how this is relevant here. This is example only of vmbus.
Look how other bindings are done. Drop the example.


> +
>              vmbus@...000000 {
>                  compatible = "microsoft,vmbus";
>                  #address-cells = <2>;
>                  #size-cells = <1>;
>                  ranges = <0x0f 0xf0000000 0x0f 0xf0000000 0x10000000>;
> +                dma-coherent;
> +                interrupt-parent = <&gic>;
> +                interrupts = <1 2 1>;

Use proper defines for known constants.

Best regards,
Krzysztof