linux-kernel - Re: [PATCH 2/3] PCI: qcom: Check for the presence of a device instead of Link up during suspend

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Message-ID: <35086b08.c4e.19a58a7d6bc.Coremail.zhangsenchuan@eswincomputing.com>
Date: Thu, 6 Nov 2025 18:13:05 +0800 (GMT+08:00)
From: zhangsenchuan <zhangsenchuan@...incomputing.com>
To: "Manivannan Sadhasivam" <manivannan.sadhasivam@....qualcomm.com>
Cc: lpieralisi@...nel.org, kwilczynski@...nel.org, mani@...nel.org,
	bhelgaas@...gle.com, will@...nel.org, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, robh@...nel.org,
	linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 2/3] PCI: qcom: Check for the presence of a device
 instead of Link up during suspend




> -----Original Messages-----
> From: "Manivannan Sadhasivam" <manivannan.sadhasivam@....qualcomm.com>
> Send time:Thursday, 06/11/2025 14:13:25
> To: lpieralisi@...nel.org, kwilczynski@...nel.org, mani@...nel.org, bhelgaas@...gle.com
> Cc: will@...nel.org, linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org, robh@...nel.org, linux-arm-msm@...r.kernel.org, zhangsenchuan@...incomputing.com, "Manivannan Sadhasivam" <manivannan.sadhasivam@....qualcomm.com>
> Subject: [PATCH 2/3] PCI: qcom: Check for the presence of a device instead of Link up during suspend
> 
> The suspend handler checks for the PCIe Link up to decide when to turn off
> the controller resources. But this check is racy as the PCIe Link can go
> down just after this check.
> 
> So use the newly introduced API, pci_root_ports_have_device() that checks
> for the presence of a device under any of the Root Ports to replace the
> Link up check.
> 
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
> ---
>  drivers/pci/controller/dwc/pcie-qcom.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index 805edbbfe7eb..b2b89e2e4916 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -2018,6 +2018,7 @@ static int qcom_pcie_probe(struct platform_device *pdev)
>  static int qcom_pcie_suspend_noirq(struct device *dev)
>  {
>  	struct qcom_pcie *pcie;
> +	struct dw_pcie_rp *pp;
>  	int ret = 0;
>  
>  	pcie = dev_get_drvdata(dev);
> @@ -2053,8 +2054,9 @@ static int qcom_pcie_suspend_noirq(struct device *dev)
>  	 * powerdown state. This will affect the lifetime of the storage devices
>  	 * like NVMe.
>  	 */
> -	if (!dw_pcie_link_up(pcie->pci)) {
> -		qcom_pcie_host_deinit(&pcie->pci->pp);
> +	pp = &pcie->pci->pp;
> +	if (!pci_root_ports_have_device(pp->bridge->bus)) {

I'm a little confused.
The pci_root_ports_have_device function can help check if there is any device 
available under the Root Ports, if there is a device available, the resource 
cannot be released, is it also necessary to release resources when entering 
the L2/L3 state?

> +		qcom_pcie_host_deinit(pp);
>  		pcie->suspended = true;
>  	}
>  
> -- 
> 2.48.1

Best Regards
Senchuan Zhang