Re: [PATCH v2 2/5] dt-bindings: net: add schema for NXP S32CC dwmac glue driver

[Krzysztof Kozlowski]

On 05/12/2022 08:54, Chester Lin wrote:
>>>>> +examples:
>>>>> +  - |
>>>>> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
>>>>> +    #include <dt-bindings/interrupt-controller/irq.h>
>>>>> +
>>>>> +    #define S32GEN1_SCMI_CLK_GMAC0_AXI
>>>>> +    #define S32GEN1_SCMI_CLK_GMAC0_TX_PCS
>>>>> +    #define S32GEN1_SCMI_CLK_GMAC0_TX_RGMII
>>>>> +    #define S32GEN1_SCMI_CLK_GMAC0_TX_RMII
>>>>> +    #define S32GEN1_SCMI_CLK_GMAC0_TX_MII
>>>>> +    #define S32GEN1_SCMI_CLK_GMAC0_RX_PCS
>>>>> +    #define S32GEN1_SCMI_CLK_GMAC0_RX_RGMII
>>>>> +    #define S32GEN1_SCMI_CLK_GMAC0_RX_RMII
>>>>> +    #define S32GEN1_SCMI_CLK_GMAC0_RX_MII
>>>>> +    #define S32GEN1_SCMI_CLK_GMAC0_TS
>>>>
>>>> Why defines? Your clock controller is not ready? If so, just use raw
>>>> numbers.
>>>
>>> Please compare v1: There is no Linux-driven clock controller here but 
>>> rather a fluid SCMI firmware interface. Work towards getting clocks into 
>>> a kernel-hosted .dtsi was halted in favor of (downstream) TF-A, which 
>>> also explains the ugly examples here and for pinctrl.
>>
>> This does not explain to me why you added defines in the example. Are
>> you saying these can change any moment?
>>
> 
> Actually these GMAC-related SCMI clock IDs changed once in NXP's downstream TF-A,
> some redundant TS clock IDs were removed and the rest of clock IDs were all moved
> forward. 

This is not accepted. Your downstream TF-A cannot change bindings. As an
upstream contributor you should push this back and definitely not try to
upstream such approach.

> Apart from GMAC-related IDs, some other clock IDs were also appended
> in both base-clock IDs and platform-specific clock IDs [The first plat ID =
> The last base ID + 1]. Due to the current design of the clk-scmi driver and the
> SCMI clock protocol, IIUC, it's better to keep all clock IDs in sequence without
> a blank in order to avoid query miss, which could affect the probe speed.

You miss here broken ABI! Any change in IDs causes all DTBs to be
broken. Downstream, upstream, other projects, everywhere.

Therefore thank you for clarifying that we need to be more careful about
stuff coming from (or for) NXP. Here you need to drop all defines and
all your patches must assume the ID is fixed. Once there, it's
unchangeable without breaking the ABI.

Best regards,
Krzysztof