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

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Message-ID: <9778695f-f8a9-e361-e28f-f99525c96689@linaro.org>
Date:   Thu, 1 Dec 2022 11:18:57 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Andreas Färber <afaerber@...e.de>,
        Chester Lin <clin@...e.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Jan Petrous <jan.petrous@....com>, Andrew Lunn <andrew@...n.ch>
Cc:     Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Jose Abreu <joabreu@...opsys.com>, netdev@...r.kernel.org,
        s32@....com, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Matthias Brugger <mbrugger@...e.com>
Subject: Re: [PATCH v2 2/5] dt-bindings: net: add schema for NXP S32CC dwmac
 glue driver

On 30/11/2022 18:33, Andreas Färber wrote:
> Hi Krysztof,
> 
> Am 30.11.22 um 16:51 schrieb Krzysztof Kozlowski:
>> On 28/11/2022 06:49, Chester Lin wrote:
>>> Add the DT schema for the DWMAC Ethernet controller on NXP S32 Common
>>> Chassis.
>>>
>>> Signed-off-by: Jan Petrous <jan.petrous@....com>
>>> Signed-off-by: Chester Lin <clin@...e.com>
>>
>> Thank you for your patch. There is something to discuss/improve.
>>
>>> ---
>>>
>>> Changes in v2:
>>>    - Fix schema issues.
>>>    - Add minItems to clocks & clock-names.
>>>    - Replace all sgmii/SGMII terms with pcs/PCS.
>>>
>>>   .../bindings/net/nxp,s32cc-dwmac.yaml         | 135 ++++++++++++++++++
>>>   1 file changed, 135 insertions(+)
>>>   create mode 100644 Documentation/devicetree/bindings/net/nxp,s32cc-dwmac.yaml
>>>
>>> diff --git a/Documentation/devicetree/bindings/net/nxp,s32cc-dwmac.yaml b/Documentation/devicetree/bindings/net/nxp,s32cc-dwmac.yaml
>>> new file mode 100644
>>> index 000000000000..c6839fd3df40
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/net/nxp,s32cc-dwmac.yaml
> [...]
>>> +properties:
>>> +  compatible:
>>> +    enum:
>>> +      - nxp,s32cc-dwmac
>>> +
>>> +  reg:
>>> +    items:
>>> +      - description: Main GMAC registers
>>> +      - description: S32 MAC control registers
>>> +
>>> +  dma-coherent: true
>>> +
>>> +  clocks:
>>> +    minItems: 5
>>
>> Why only 5 clocks are required? Receive clocks don't have to be there?
>> Is such system - only with clocks for transmit - usable?

Any comments here? If not, drop minItems.

>>
>>> +    items:
>>> +      - description: Main GMAC clock
>>> +      - description: Peripheral registers clock
>>> +      - description: Transmit PCS clock
>>> +      - description: Transmit RGMII clock
>>> +      - description: Transmit RMII clock
>>> +      - description: Transmit MII clock
>>> +      - description: Receive PCS clock
>>> +      - description: Receive RGMII clock
>>> +      - description: Receive RMII clock
>>> +      - description: Receive MII clock
>>> +      - description:
>>> +          PTP reference clock. This clock is used for programming the
>>> +          Timestamp Addend Register. If not passed then the system
>>> +          clock will be used.
>>> +
>>> +  clock-names:
>>> +    minItems: 5
>>> +    items:
>>> +      - const: stmmaceth
>>> +      - const: pclk
>>> +      - const: tx_pcs
>>> +      - const: tx_rgmii
>>> +      - const: tx_rmii
>>> +      - const: tx_mii
>>> +      - const: rx_pcs
>>> +      - const: rx_rgmii
>>> +      - const: rx_rmii
>>> +      - const: rx_mii
>>> +      - const: ptp_ref
>>> +
>>> +  tx-fifo-depth:
>>> +    const: 20480
>>> +
>>> +  rx-fifo-depth:
>>> +    const: 20480
>>> +
>>> +required:
>>> +  - compatible
>>> +  - reg
>>> +  - tx-fifo-depth
>>> +  - rx-fifo-depth
>>> +  - clocks
>>> +  - clock-names
>>> +
>>> +unevaluatedProperties: false
>>> +
>>> +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?

> 
> Logically there are only 5 input clocks; however due to SCMI not 
> supporting re-parenting today, some clocks got duplicated at SCMI level. 
> Andrew appeared to approve of that approach. I still dislike it but 
> don't have a better proposal that would work today. So the two values 
> above indeed seem wrong and should be 11 rather than 5.

You should rather fix firmware then create some incorrect bindings as a
workaround...

Best regards,
Krzysztof