Re: [PATCH RFC v4 1/4] media: dt-bindings: Add Amlogic V4L2 video decoder

[Krzysztof Kozlowski <krzk@kernel.org>]

On 13/02/2026 09:02, Zhentao Guo wrote:
> Hi Krzysztof,
> 
> 
> 在 2026/2/13 15:35, Krzysztof Kozlowski 写道:
>> [ EXTERNAL EMAIL ]
>>
>> On 13/02/2026 06:12, Zhentao Guo via B4 Relay wrote:
>>> From: Zhentao Guo<zhentao.guo@amlogic.com>
>>>
>>> Describe the initial support for the V4L2 stateless video decoder
>>> driver used with the Amlogic S4 (S805X2) platform.
>>>
>>> Signed-off-by: Zhentao Guo<zhentao.guo@amlogic.com>
>>> ---
>>>   .../bindings/media/amlogic,s4-vcodec-dec.yaml      | 96 ++++++++++++++++++++++
>>>   1 file changed, 96 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/media/amlogic,s4-vcodec-dec.yaml b/Documentation/devicetree/bindings/media/amlogic,s4-vcodec-dec.yaml
>>> new file mode 100644
>>> index 000000000000..88780514d06c
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/media/amlogic,s4-vcodec-dec.yaml
>>> @@ -0,0 +1,96 @@
>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>> +# Copyright (C) 2025 Amlogic, Inc. All rights reserved
>>> +%YAML 1.2
>>> +---
>>> +$id:http://devicetree.org/schemas/media/amlogic,s4-vcodec-dec.yaml#
>>> +$schema:http://devicetree.org/meta-schemas/core.yaml#
>>> +
>>> +title: Amlogic Video Decode Accelerator
>>> +
>>> +maintainers:
>>> +  - Zhentao Guo<zhentao.guo@amlogic.com>
>>> +
>>> +description:
>>> +  The Video Decoder Accelerator present on Amlogic SOCs.
>>> +  It supports stateless h264 decoding.
>>> +
>>> +properties:
>>> +  compatible:
>>> +    const: amlogic,s4-vcodec-dec
>> Why do you repeat "dec" twice? codec means decoder, so what is the last
>> "dec" about?
> In fact, codec means encoder+decoder, and dec is short for decoder.

Yes, that's what I meant, so why do you repeat decoder?

>>> +
>>> +  reg:
>>> +    maxItems: 2
>>> +
>>> +  reg-names:
>>> +    items:
>>> +      - const: dos
>>> +      - const: dmc
>>> +
>>> +  interrupts:
>>> +    maxItems: 3
>>> +
>>> +  clocks:
>>> +    maxItems: 3
>>> +
>>> +  clock-names:
>>> +    items:
>>> +      - const: vdec
>>> +      - const: clk_vdec_mux
>>> +      - const: clk_hevcf_mux
>> Name them based on their role/name in this device. Why this device would
>> care that it receives a mux? Not a div? or not a gate?
> Ok, previously we overlooked this. We will improve it in the next version.
>>> +
>>> +  power-domains:
>>> +    maxItems: 2
>>> +
>>> +  power-domain-names:
>>> +    items:
>>> +      - const: vdec
>>> +      - const: hevc
>>> +
>>> +  resets:
>>> +    maxItems: 1
>>> +
>>> +  amlogic,canvas:
>>> +    description: should point to a canvas provider node
>> Why? What for?
>>
>> What is canvas provider?
> 
> The canvas provider is: drivers/soc/amlogic/meson-canvas.c

What is this "canvas" device.

> 
> In short, canvas is a hardware IP inside the Amlogic SoC. The decoder IP 
> needs to access DDR through canvas IP, so we need to reference the 

Why decoder cannot access DDR directly?


Best regards,
Krzysztof