linux-kernel - Re: [PATCH v4 3/5] dt-bindings: media: Add the Raspberry Pi HEVC decoder

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Message-ID: <4cbd47f8211e3e1a038857f848ad4197d95bd31c.camel@ndufresne.ca>
Date: Fri, 07 Nov 2025 11:33:07 -0500
From: Nicolas Dufresne <nicolas@...fresne.ca>
To: Dave Stevenson <dave.stevenson@...pberrypi.com>, Sakari Ailus	
 <sakari.ailus@...ux.intel.com>, Laurent Pinchart	
 <laurent.pinchart@...asonboard.com>, Mauro Carvalho Chehab
 <mchehab@...nel.org>,  Rob Herring <robh@...nel.org>, Krzysztof Kozlowski
 <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>,  Florian Fainelli
 <florian.fainelli@...adcom.com>, Broadcom internal kernel review list	
 <bcm-kernel-feedback-list@...adcom.com>, John Cox
 <john.cox@...pberrypi.com>,  Dom Cobley <dom@...pberrypi.com>, review list
 <kernel-list@...pberrypi.com>, Ezequiel Garcia	
 <ezequiel@...guardiasur.com.ar>
Cc: John Cox <jc@...esim.co.uk>, Stefan Wahren <wahrenst@....net>, 
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org, 
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v4 3/5] dt-bindings: media: Add the Raspberry Pi HEVC
 decoder

Le mardi 01 juillet 2025 à 17:01 +0100, Dave Stevenson a écrit :
> Adds a binding for the HEVC decoder IP owned by Raspberry Pi.
> 
> Instantiations of the decoder IP can currently be found in
> the Broadcom BCM2711 and BCM2712 SoCs.
> 
> Signed-off-by: Dave Stevenson <dave.stevenson@...pberrypi.com>
> 
> ---
> 
> Updated based on the thread in v3 [1] with Krzystof to drop to only SoC
> specific compatible strings.
> 
> This still feels wrong to me as this is NOT Broadcom IP - it is solely
> owned by Raspberry Pi.
> 
> It is the same situation as for the Raspberry Pi ISP Backend where
> it was proposed to have
>   compatible = "brcm,pispbe-bcm2712", "raspberrypi,pispbe";
> in [2]. That proposal was viewed as acceptable by both Rob[3] and Conor[4],
> and the binding given a Reviewed-by by Rob[5].
> 
> Yes it is found as a block inside an SoC, but the same could be said
> for a Synopsys I2C controller ("snps,designware-i2c"), Cadence ethernet
> MAC ("cdns,macb"), ARM CPU (eg "arm,cortex-a53"), or any number of other
> examples. They are all 3rd party IP blocks found in SoCs, have an SoC specific
> compatible defined, but acknowledge the IP owner and use a common fallback
> compatible where possible.
> 
> Please could we have confirmation that this really is what is required
> by device tree?

Its been approved like this, are you confortable with that now ? If I'm reading
this correctly, its common practice to add and use a SoC specific compatible
just in case some variation exists. Its quite unlikely in this case of course.

cheers,
Nicolas

> 
> Thanks
>   Dave
> 
> [1] https://lore.kernel.org/linux-media/20250423-media-rpi-hevc-dec-v3-3-8fd3fad1d6fb@raspberrypi.com/
> [2] https://lore.kernel.org/linux-media/20240213104405.GB5012@pendragon.ideasonboard.com/
> [3] https://lore.kernel.org/linux-media/20240215140058.GA4147262-robh@kernel.org/
> [4] https://lore.kernel.org/linux-media/20240213-landlady-backstab-6e7da824c99a@spud/
> [5] https://lore.kernel.org/linux-media/170932821578.3062059.18150159256247255021.robh@kernel.org/
> ---
>  .../bindings/media/raspberrypi,hevc-dec.yaml       | 72 ++++++++++++++++++++++
>  1 file changed, 72 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/media/raspberrypi,hevc-dec.yaml b/Documentation/devicetree/bindings/media/raspberrypi,hevc-dec.yaml
> new file mode 100644
> index 000000000000..fe3361bddd1f
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/media/raspberrypi,hevc-dec.yaml
> @@ -0,0 +1,72 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/media/raspberrypi,hevc-dec.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Raspberry Pi HEVC Decoder
> +
> +maintainers:
> +  - John Cox <john.cox@...pberrypi.com>
> +  - Dom Cobley <dom@...pberrypi.com>
> +  - Dave Stevenson <dave.stevenson@...pberrypi.com>
> +
> +description:
> +  The Raspberry Pi HEVC decoder is a hardware video decode accelerator IP block
> +  developed and owned by Raspberry Pi.
> +
> +  Currently it can be found in the Broadcom BCM2711 and BCM2712 processors used
> +  on Raspberry Pi 4 and 5 boards respectively.
> +
> +properties:
> +  compatible:
> +    oneOf:
> +      - const: brcm,bcm2711-hevc-dec
> +      - items:
> +          - enum:
> +              - brcm,bcm2712-hevc-dec
> +          - const: brcm,bcm2711-hevc-dec
> +
> +  reg:
> +    items:
> +      - description: The HEVC main register region
> +      - description: The Interrupt control register region
> +
> +  reg-names:
> +    items:
> +      - const: hevc
> +      - const: intc
> +
> +  interrupts:
> +    maxItems: 1
> +
> +  clocks:
> +    items:
> +      - description: The HEVC block clock
> +
> +required:
> +  - compatible
> +  - reg
> +  - reg-names
> +  - interrupts
> +  - clocks
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
> +
> +    video-codec@...10000 {
> +        compatible = "brcm,bcm2711-hevc-dec";
> +        reg = <0x7eb00000 0x10000>, /* HEVC */
> +              <0x7eb10000 0x1000>;  /* INTC */
> +        reg-names = "hevc",
> +                    "intc";
> +
> +        interrupts = <GIC_SPI 98 IRQ_TYPE_LEVEL_HIGH>;
> +
> +        clocks = <&clk 0>;
> +    };
> +
> +...

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