linux-kernel - Re: [PATCH v4 1/6] PCI: dwc: Return -ENODEV from dw_pcie_wait_for

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Message-ID: <f9ccb38b-0471-4fe4-9492-2d8abd816a50@rock-chips.com>
Date: Wed, 7 Jan 2026 16:34:19 +0800
From: Shawn Lin <shawn.lin@...k-chips.com>
To: manivannan.sadhasivam@....qualcomm.com, Jingoo Han
 <jingoohan1@...il.com>, Manivannan Sadhasivam <mani@...nel.org>,
 Lorenzo Pieralisi <lpieralisi@...nel.org>,
 Krzysztof Wilczyński <kwilczynski@...nel.org>,
 Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>
Cc: shawn.lin@...k-chips.com, linux-pci@...r.kernel.org,
 linux-kernel@...r.kernel.org, vincent.guittot@...aro.org,
 zhangsenchuan@...incomputing.com, Richard Zhu <hongxing.zhu@....com>
Subject: Re: [PATCH v4 1/6] PCI: dwc: Return -ENODEV from
 dw_pcie_wait_for_link() if device is not found

在 2026/01/07 星期三 16:11, Manivannan Sadhasivam via B4 Relay 写道:
> From: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
> 
> The dw_pcie_wait_for_link() function waits up to 1 second for the PCIe link
> to come up and returns -ETIMEDOUT for all failures without distinguishing
> cases where no device is present on the bus. But the callers may want to
> just skip the failure if the device is not found on the bus and handle
> failure for other reasons.
> 
> So after timeout, if the LTSSM is in Detect.Quiet or Detect.Active state,
> return -ENODEV to indicate the callers that the device is not found on the
> bus and return -ETIMEDOUT otherwise.
> 
> Also add kernel doc to document the parameter and return values.
> 

Reviewed-by: Shawn Lin <shawn.lin@...k-chips.com>

> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
> ---
>   drivers/pci/controller/dwc/pcie-designware.c | 20 +++++++++++++++++++-
>   1 file changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> index 345365ea97c7..55c1c60f7f8f 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -692,9 +692,16 @@ void dw_pcie_disable_atu(struct dw_pcie *pci, u32 dir, int index)
>   	dw_pcie_writel_atu(pci, dir, index, PCIE_ATU_REGION_CTRL2, 0);
>   }
>   
> +/**
> + * dw_pcie_wait_for_link - Wait for the PCIe link to be up
> + * @pci: DWC instance
> + *
> + * Returns: 0 if link is up, -ENODEV if device is not found, -ETIMEDOUT if the
> + * link fails to come up for other reasons.
> + */
>   int dw_pcie_wait_for_link(struct dw_pcie *pci)
>   {
> -	u32 offset, val;
> +	u32 offset, val, ltssm;
>   	int retries;
>   
>   	/* Check if the link is up or not */
> @@ -706,6 +713,17 @@ int dw_pcie_wait_for_link(struct dw_pcie *pci)
>   	}
>   
>   	if (retries >= PCIE_LINK_WAIT_MAX_RETRIES) {
> +		/*
> +		 * If the link is in Detect.Quiet or Detect.Active state, it
> +		 * indicates that no device is detected.
> +		 */
> +		ltssm = dw_pcie_get_ltssm(pci);
> +		if (ltssm == DW_PCIE_LTSSM_DETECT_QUIET ||
> +		    ltssm == DW_PCIE_LTSSM_DETECT_ACT) {
> +			dev_info(pci->dev, "Device not found\n");
> +			return -ENODEV;
> +		}
> +
>   		dev_info(pci->dev, "Phy link never came up\n");
>   		return -ETIMEDOUT;
>   	}
>