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

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Message-ID: <ei7qtgj7jegwaafrjdccoaz3tg7klnms4dyiqdumwxdvnucp4c@euose4y6vkqg>
Date: Tue, 26 Aug 2025 15:50:07 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Krzysztof Kozlowski <krzk@...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 Tue, Aug 26, 2025 at 11:29:37AM GMT, Krzysztof Kozlowski wrote:
> 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.
> 

Compatibles for the PCI bridges are not mandatory, so we cannot use it. But
'device_type' is and Krishna is going to use that instead.

- Mani

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