Re: [PATCH v6 08/30] dt-bindings: soc: fsl: cpm_qe: cpm1-scc-qmc: Add support for QMC HDLC

[Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>]

On 25/09/2023 10:17, Herve Codina wrote:
> Hi Krzysztof,
> 
> On Sat, 23 Sep 2023 19:39:49 +0200
> Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx> wrote:
> 
>> On 22/09/2023 09:58, Herve Codina wrote:
>>> The QMC (QUICC mutichannel controller) is a controller present in some
>>> PowerQUICC SoC such as MPC885.
>>> The QMC HDLC uses the QMC controller to transfer HDLC data.
>>>
>>> Additionally, a framer can be connected to the QMC HDLC.
>>> If present, this framer is the interface between the TDM bus used by the
>>> QMC HDLC and the E1/T1 line.
>>> The QMC HDLC can use this framer to get information about the E1/T1 line
>>> and configure the E1/T1 line.
>>>
>>> Signed-off-by: Herve Codina <herve.codina@xxxxxxxxxxx>
>>> ---
>>>  .../soc/fsl/cpm_qe/fsl,cpm1-scc-qmc.yaml      | 24 +++++++++++++++++++
>>>  1 file changed, 24 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/soc/fsl/cpm_qe/fsl,cpm1-scc-qmc.yaml b/Documentation/devicetree/bindings/soc/fsl/cpm_qe/fsl,cpm1-scc-qmc.yaml
>>> index 82d9beb48e00..61dfd5ef7407 100644
>>> --- a/Documentation/devicetree/bindings/soc/fsl/cpm_qe/fsl,cpm1-scc-qmc.yaml
>>> +++ b/Documentation/devicetree/bindings/soc/fsl/cpm_qe/fsl,cpm1-scc-qmc.yaml
>>> @@ -101,6 +101,27 @@ patternProperties:
>>>            Channel assigned Rx time-slots within the Rx time-slots routed by the
>>>            TSA to this cell.
>>>  
>>> +      compatible:
>>> +        const: fsl,qmc-hdlc  
>>
>> Why this is not a device/SoC specific compatible?
> 
> This compatible is present in a QMC channel.
> The parent node (the QMC itself) contains a compatible with device/SoC:
> --- 8< ---
>   compatible:
>     items:
>       - enum:
>           - fsl,mpc885-scc-qmc
>           - fsl,mpc866-scc-qmc
>       - const: fsl,cpm1-scc-qmc
> --- 8< ---
> 
> At the child level (ie QMC channel), I am not sure that adding device/SoC
> makes sense. This compatible indicates that the QMC channel is handled by
> the QMC HDLC driver.
> At this level, whatever the device/SoC, we have to be QMC compliant.
> 
> With these details, do you still think I need to change the child (channel)
> compatible ?

>From OS point of view, you have a driver binding to this child-level
compatible. How do you enforce Linux driver binding based on parent
compatible? I looked at your next patch and I did not see it.

Best regards,
Krzysztof