Re: [PATCH net-next v2 2/3] dt-bindings: net: add T-HEAD dwmac support

[Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>]

On 28/08/2023 17:51, Serge Semin wrote:
> On Mon, Aug 28, 2023 at 11:17:36PM +0800, Jisheng Zhang wrote:
>> On Mon, Aug 28, 2023 at 04:13:00PM +0300, Serge Semin wrote:
>>> On Sun, Aug 27, 2023 at 05:17:09PM +0800, Jisheng Zhang wrote:
>>>> Add documentation to describe T-HEAD dwmac.
>>>>
>>>> Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
>>>> ---
>>>>  .../devicetree/bindings/net/snps,dwmac.yaml   |  1 +
>>>>  .../devicetree/bindings/net/thead,dwmac.yaml  | 77 +++++++++++++++++++
>>>>  2 files changed, 78 insertions(+)
>>>>  create mode 100644 Documentation/devicetree/bindings/net/thead,dwmac.yaml
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/net/snps,dwmac.yaml b/Documentation/devicetree/bindings/net/snps,dwmac.yaml
>>>> index b196c5de2061..73821f86a609 100644
>>>> --- a/Documentation/devicetree/bindings/net/snps,dwmac.yaml
>>>> +++ b/Documentation/devicetree/bindings/net/snps,dwmac.yaml
>>>> @@ -96,6 +96,7 @@ properties:
>>>>          - snps,dwxgmac
>>>>          - snps,dwxgmac-2.10
>>>>          - starfive,jh7110-dwmac
>>>> +        - thead,th1520-dwmac
>>>>  
>>>>    reg:
>>>>      minItems: 1
>>>> diff --git a/Documentation/devicetree/bindings/net/thead,dwmac.yaml b/Documentation/devicetree/bindings/net/thead,dwmac.yaml
>>>> new file mode 100644
>>>> index 000000000000..bf8ec8ca2753
>>>> --- /dev/null
>>>
>>>> +++ b/Documentation/devicetree/bindings/net/thead,dwmac.yaml
>>>
>>> see further regarding using dwmac in the names here.
>>>
>>>> @@ -0,0 +1,77 @@
>>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>>> +%YAML 1.2
>>>> +---
>>>> +$id: http://devicetree.org/schemas/net/thead,dwmac.yaml#
>>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>>> +
>>>
>>>> +title: T-HEAD DWMAC Ethernet controller
>>>
>>> Additionally would be nice to have a brief controller "description:"
>>> having the next info: the SoCs the controllers can be found on, the DW
>>> (G)MAC IP-core version the ethernet controller is based on and some
>>> data about the synthesize parameters: SMA (MDIO-bus), Tx/Rx COE, DMA
>>> FIFOs size, perfect and hash MAC-filters size, L3L4 frame filters
>>> availability, VLAN hash filter, SA/VLAN-tag insertion, ARP offload
>>> engine, PHY interfaces (MII, RMII, RGMII, etc), EEE support, IEEE
>>> 1588(-2008) Timestamping support, PMT and Wake-up frame support, MAC
>>> Management counters (MMC). In addition to that for DW QoS
>>> ETH/XGMAC/XLGMAC the next info would be useful: number of MTL Queues
>>> and DMA channels, MTL queues capabilities (QoS-related), TSO
>>> availability, SPO availability.
>>>
> 
>>> Note DMA FIFO sizes can be also constrained in the properties
>>> "rx-fifo-depth" and "tx-fifo-depth"; perfect and hash MAC-filter sizes -
>>> in "snps,perfect-filter-entries" and "snps,multicast-filter-bins".
> 
> BTW plus to this you may wish to add the "rx-internal-delay-ps" and
> "tx-internal-delay-ps" properties constraints seeing they device
> supports internal Tx/Rx delays.
> 
>>
>> Hi Serge,
>>
> 
>> Thank you for your code review. I have different views here: If we
>> only support the gmac controller in one specific SoC, these detailed
>> information is nice to have, but what about if the driver/dt-binding
>> supports the gmac controller in different SoCs? These detailed
>> information will be outdated.
> 
> First they won't. Second then you can either add more info to the
> description for instance in a separate paragraph or create a dedicated
> DT-bindings. Such information would be very much useful for the
> generic STMMAC driver code maintenance.
> 
>>
>> what's more, I think the purpose of dt-binding is different from
>> the one of documentation.
> 
> The purpose of the DT-bindings is a hardware "description". The info I
> listed describes your hardware.
> 
>>
>> So I prefer to put these GMAC IP related detailed information into
>> the SoC's dtsi commit msg rather than polluting the dt-binding.
>>>
>>>> +
>>>> +maintainers:
>>>> +  - Jisheng Zhang <jszhang@kernel.org>
>>>> +
>>>> +select:
>>>> +  properties:
>>>> +    compatible:
>>>> +      contains:
>>>> +        enum:
>>>
>>>> +          - thead,th1520-dwmac
>>>
>>> Referring to the DW IP-core in the compatible string isn't very
>>> much useful especially seeing you have a generic fallback compatible.
>>> Name like "thead,th1520-gmac" looks more informative indicating its
>>> speed capability.
>>
> 
>> This is just to follow the common style as those dwmac-* does.
>> I'm not sure which is better, but personally, I'd like to keep current
>> common style.
> 
> It's not that common. Half the compatible strings use the notation
> suggested by me and it has more sense then a dwmac suffix. It's ok to
> use the suffix in the STMMAC driver-related things because the glue
> code is supposed to work with the DW *MAC generic code. Using it in
> the compatible string especially together with the generic fallback
> compatible just useless.

THEAD did not make dwmac here, but a gmac. dwmac does not exist in the
context of Thead and Th1520, so the naming suggested by Serge makes sense.

Best regards,
Krzysztof