Re: [PATCH v3 1/3] media: dt-bindings: rockchip,vdec: Add alternative reg-names order for RK35{76,88}

[Krzysztof Kozlowski]

On 25/02/2026 14:36, Cristian Ciocaltea wrote:
> On 2/25/26 2:26 PM, Krzysztof Kozlowski wrote:
>> On 25/02/2026 13:19, Cristian Ciocaltea wrote:
>>> With the introduction of the RK3588 SoC, and RK3576 afterwards, the
>>> 'link' and 'cache' register blocks have been provided for the video
>>> decoder unit in addition to the existing 'function' one, which now shows
>>> up in between them (from address-based ordering point of view).
>>>
>>> However, the binding does not properly describe this hardware layout, as
>>> the new blocks are listed after the old one.  Therefore it breaks the
>>> convention expecting the unit address to indicate the first register
>>> range.
>>>
>>> Since the binding changes have been already released and a fix would
>>> bring up an ABI break, mark the current 'reg-names' listing as
>>> deprecated and introduce an alternative 'link,function,cache' one.
>>>
>>> Additionally, drop the 'reg' description items as the order is not fixed
>>> anymore, while the information they offer is not very relevant anyway.
>>>
>>> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@xxxxxxxxxxxxx>
>>> ---
>>>  .../devicetree/bindings/media/rockchip,vdec.yaml      | 19 ++++++++++++-------
>>>  1 file changed, 12 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/Documentation/devicetree/bindings/media/rockchip,vdec.yaml b/Documentation/devicetree/bindings/media/rockchip,vdec.yaml
>>> index 809fda45b3bd..3f6072e8baa5 100644
>>> --- a/Documentation/devicetree/bindings/media/rockchip,vdec.yaml
>>> +++ b/Documentation/devicetree/bindings/media/rockchip,vdec.yaml
>>> @@ -28,16 +28,21 @@ properties:
>>>  
>>>    reg:
>>>      minItems: 1
>>> -    items:
>>> -      - description: The function configuration registers base
>>> -      - description: The link table configuration registers base
>>> -      - description: The cache configuration registers base
>>> +    maxItems: 3
>>>  
>>>    reg-names:
>>> -    items:
>>> +    oneOf:
>>>        - const: function
>>
>> This is confusing, I think I missed that in previous patch because it
>> did not leave that part or I misread the diff hunk - why do you allow
>> one entry?
> 
> That's for the older SoCs, e.g. RK3288, RK3399, as the 'link' and 'cache' blocks
> are only available for RK3576 & RK3588.

Yeah, I see in the bottom of the binding

> 
>>
>> If the first entry is function, then all others MUST built on top, thus
>> this:
>>
>>> +          - const: link
>>> +          - const: function
>>> +          - const: cache
>>
>> is not correct.
>>
>> No, you don't change the orders. So again, if you have such binding,
>> then you just fix the unit address leaving the binding as is.
> 
> Changing the unit address would mean it will point inside the register range,
> rather than at the beginning of it.

First, not true. If this was one register range, you would have one
entry. You cannot split entries. Split entries means you have two
SEPARATE register ranges.
Second, it does not matter because main rule stays - the unit address
describes the main address space. The main address space in other device
was called "function", so I assume the main address space is also here
the "function". Which makes sense, because link feels secondary to
functioning of the device.

> 
> Sorry, but I don't quite get why would this be a better approach than just
> properly list the items according to the HW layout, i.e. following the
> address-based ordering?

We always expect the list to grow, to have common set. That's rule given
during reviews multiple times. For multiple reasons, also explained
(consistency, maintenance and actually proper description of hardware
like the main reg address space).

Probably this was also given to that binding during discussions when it
was upstream, so your change reverts previous discussion and to that I
do not agree.

Best regards,
Krzysztof