linux-kernel - Re: [PATCH v2 3/3] PCI: qcom: Restrict port parsing only to pci child nodes

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Message-ID: <dfd9cc8b-8103-4fa9-8b3b-c31ae7c4970a@kernel.org>
Date: Tue, 26 Aug 2025 11:29:37 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Manivannan Sadhasivam <mani@...nel.org>
Cc: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>,
 Vinod Koul <vkoul@...nel.org>, Kishon Vijay Abraham I <kishon@...nel.org>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Lorenzo Pieralisi
 <lpieralisi@...nel.org>, Krzysztof Wilczyński
 <kwilczynski@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
 Bjorn Andersson <andersson@...nel.org>,
 Konrad Dybcio <konradybcio@...nel.org>, linux-arm-msm@...r.kernel.org,
 linux-phy@...ts.infradead.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
 quic_vbadigan@...cinc.com, quic_mrana@...cinc.com
Subject: Re: [PATCH v2 3/3] PCI: qcom: Restrict port parsing only to pci child
 nodes

On 26/08/2025 11:26, Manivannan Sadhasivam wrote:
> On Tue, Aug 26, 2025 at 10:28:51AM GMT, Krzysztof Kozlowski wrote:
>> On 26/08/2025 08:17, Manivannan Sadhasivam wrote:
>>> On Tue, Aug 26, 2025 at 10:48:19AM GMT, Krishna Chaitanya Chundru wrote:
>>>> The qcom_pcie_parse_ports() function currently iterates over all available
>>>> child nodes of the PCIe controller's device tree node. This can lead to
>>>> attempts to parse unrelated nodes like OPP nodes, resulting in unnecessary
>>>> errors or misconfiguration.
>>>>
>>>
>>> What errors? Errors you are seeing on your setup or you envision?
>>>
>>>> Restrict the parsing logic to only consider child nodes named "pcie" or
>>>> "pci", which are the expected node names for PCIe ports.
>>>>
>>>> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
>>>
>>> Since this is a fix, 'Fixes' tag is needed.
>>>
>>>> ---
>>>>  drivers/pci/controller/dwc/pcie-qcom.c | 2 ++
>>>>  1 file changed, 2 insertions(+)
>>>>
>>>> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
>>>> index 294babe1816e4d0c2b2343fe22d89af72afcd6cd..5dbdb69fbdd1b9b78a3ebba3cd50d78168f2d595 100644
>>>> --- a/drivers/pci/controller/dwc/pcie-qcom.c
>>>> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
>>>> @@ -1740,6 +1740,8 @@ static int qcom_pcie_parse_ports(struct qcom_pcie *pcie)
>>>>  	int ret = -ENOENT;
>>>>  
>>>>  	for_each_available_child_of_node_scoped(dev->of_node, of_port) {
>>>> +		if (!(of_node_name_eq(of_port, "pcie") || of_node_name_eq(of_port, "pci")))
>>>
>>> May I know which platform has 'pci' as the node name for the bridge node? AFAIK,
>>> all platforms defining bridge nodes have 'pcie' as the node name.
>>
>> It does not matter. If I name my node name as "pc" it stops working?
>>
>> No, Qualcomm cannot introduce such hidden ABI.
> 
> There is no hidden ABI that Qcom is introducing. We are just trying to reuse the
> standard node names documented in the devicetree spec. So you are saying that
> we should not rely on it even though it is documented? Maybe because, the dt
> tooling is not yet screaming if people put non-standard names in DT?
> 

If it is documented, you can use it, but I doubted first the author even
checked that. Otherwise commit message would say that.

As I mentioned in other response, I still find it discouraged pattern if
you have (and you do have!) compatibles.


Best regards,
Krzysztof