Re: [PATCH v4 01/20] dt-bindings: phy: Add starfive,jh7110-inno-hdmi-phy

[Krzysztof Kozlowski]

On 03/10/2026 17:36, Michal Wilczynski wrote:
> 
> 
> On 9/30/26 13:01, Krzysztof Kozlowski wrote:
>> On 25/09/2026 23:05, Michal Wilczynski wrote:
>>>>> +  clocks:
>>>>> +    maxItems: 1
>>>>> +    description: Reference oscillator.
>>>>
>>>> This barely counts as a resource, so usual question: no resources here?
>>>> no MMIO? Even the user of this phy is the block itself.
>>>>
>>>> This makes me wonder if this should be a device node in the first place
>>>> (instead folded into the parent).
>>>
>>> The PHY has no reg because the reg is shared with the controller and
>>> owned by the parent - patch 9 lets the bridge take its regmap from
>>> there.
>>>
>>> The user of the PHY is not only the block itself. It is the pixel clock
>>> provider for the whole display subsystem, voutcrg takes hdmitx0_pixelclk
>>> as the parent of its DC8200 pixel MUXes, and while HDMI output is active
>>> it is the only intended source for that clock. The parent has to be
>>> assigned explicitly so the general PLL does not end up driving the pixel
>>> clock, and so a DSI user does not reach the HDMI PHY clock generator.
>>>
>>> So it has to be its own node. The HDMI block has two independent
>>
>> I do not see the logic which lead to this conclusion. Pixel clock
>> provider, so a clock controller, cannot be a user of a phy. Clock
>> controller does not have a physical layer.
> 
> Sorry I think the wording was not perfect. I meant the PHY node is a
> pixel clock provider. voutcrg consumes a clock not a PHY.
> 
> voutcrg: clock-controller@295c0000 {
>          clocks = <&syscrg ...>, <&hdmi_phy>;
>          clock-names = ...,"hdmitx0_pixelclk";
> };
> 
> The consumer of the PHY is only the hdmi controller.
> 
> What matters for the node layout is where that clock goes. voutcrg is the
> SoC display clock controller - it is not part of the HDMI block:
> 
> hdmi_phy -- pixel clock -> voutcrg
>                               |
>                               - pclk/mclk/bclk -> hdmi_controller
>                               - pix0/pix1 -> dc8200
> 
> hdmi_phy and hdmi_controller are the same register block with one reg
> owned by the parent. So if that block is described as a single node:
> 
> hdmi_node - pixel clock -> voutcrg
>      ^                          |
>      --- pclk/mclk/bclk --------
> 
> the node provides a clock to voutcrg and consumes three clocks from
> voutcrg. That is a cycle in the device tree description.

There is no cycle. Internal signals to the block are not represented in DT.

What you have is a driver problem and you create some sort of DT
structure to solve that. DT purpose is NOT to solve your driver
dependencies or circular connections.

Best regards,
Krzysztof