linux-kernel - Re: [PATCH 2/3] net: stmmac: qcom-ethqos: Enable RX programmable swap on qcs615

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Message-ID: <0d2ebb1c-be69-45ca-8a66-4e4a8ca59513@kernel.org>
Date: Mon, 13 Jan 2025 12:26:00 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Yijie Yang <quic_yijiyang@...cinc.com>, Vinod Koul <vkoul@...nel.org>,
 Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Bjorn Andersson <andersson@...nel.org>,
 Konrad Dybcio <konradybcio@...nel.org>,
 Alexandre Torgue <alexandre.torgue@...s.st.com>,
 Jose Abreu <joabreu@...opsys.com>,
 Maxime Coquelin <mcoquelin.stm32@...il.com>
Cc: netdev@...r.kernel.org, linux-arm-msm@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/3] net: stmmac: qcom-ethqos: Enable RX programmable swap
 on qcs615

On 08/01/2025 11:33, Yijie Yang wrote:
> 
> 
> On 2024-12-27 15:03, Krzysztof Kozlowski wrote:
>> On 26/12/2024 03:29, Yijie Yang wrote:
>>>
>>>
>>> On 2024-12-25 19:37, Krzysztof Kozlowski wrote:
>>>> On 25/12/2024 11:04, Yijie Yang wrote:
>>>>
>>>>>    static int qcom_ethqos_probe(struct platform_device *pdev)
>>>>>    {
>>>>> -	struct device_node *np = pdev->dev.of_node;
>>>>> +	struct device_node *np = pdev->dev.of_node, *root;
>>>>>    	const struct ethqos_emac_driver_data *data;
>>>>>    	struct plat_stmmacenet_data *plat_dat;
>>>>>    	struct stmmac_resources stmmac_res;
>>>>> @@ -810,6 +805,15 @@ static int qcom_ethqos_probe(struct platform_device *pdev)
>>>>>    	ret = of_get_phy_mode(np, &ethqos->phy_mode);
>>>>>    	if (ret)
>>>>>    		return dev_err_probe(dev, ret, "Failed to get phy mode\n");
>>>>> +
>>>>> +	root = of_find_node_by_path("/");
>>>>> +	if (root && of_device_is_compatible(root, "qcom,sa8540p-ride"))
>>>>
>>>>
>>>> Nope, your drivers are not supposed to poke root compatibles. Drop and
>>>> fix your driver to behave correctly for all existing devices.
>>>>
>>>
>>> Since this change introduces a new flag in the DTS, we must maintain ABI
>>> compatibility with the kernel. The new flag is specific to the board, so
>>
>> It's not, I don't see it specific to the board in the bindings.
> 
> I'm sorry for the confusion. This feature is not board-specific but 
> rather a tunable option. All RGMII boards can choose whether to enable 
> this bit in the DTS, so there are no restrictions in the binding.

If it is not specific to the board, I don't see why this cannot be
implied by compatible.

> 
>>
>>> I need to ensure root nodes are matched to allow older boards to
>>> continue functioning as before. I'm happy to adopt that approach if
>>> there are any more elegant solutions.
>>
>> I don't think you understood the problem. Why you are not handling this
>> for my board, sa8775p-rideX and sa8225-pre-ride-yellow-shrimp?
>>
> 
> This feature is specifically for RGMII boards. The driver won't enable 

So board specific?

> this bit if the DTS doesn't specify it. To handle compatibility, we need 

Do not describe us how drivers and DTS work. We all know.

> to identify legacy RGMII boards with MAC versions greater or equal to 3 
> which require this bit to be enabled.
> According to my knowledge, the SA8775P is of the SGMII type.

Best regards,
Krzysztof