linux-kernel - Re: [PATCH v4 2/5] PCI: dwc: Return -EIO from dw_pcie_wait_for

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Message-ID: <wswb6we7iyp3co5u7wcntqogtqmqitbmty5ihqnweno7efdpoh@gekgtcp262zw>
Date: Wed, 21 Jan 2026 14:43:03 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
To: Niklas Cassel <cassel@...nel.org>
Cc: 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>, linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org, 
	vincent.guittot@...aro.org, zhangsenchuan@...incomputing.com, 
	Shawn Lin <shawn.lin@...k-chips.com>, Richard Zhu <hongxing.zhu@....com>
Subject: Re: [PATCH v4 2/5] PCI: dwc: Return -EIO from
 dw_pcie_wait_for_link() if device is not active

On Wed, Jan 21, 2026 at 09:23:22AM +0100, Niklas Cassel wrote:
> On Tue, Jan 20, 2026 at 11:17:41PM +0530, Manivannan Sadhasivam via B4 Relay wrote:
> > From: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
> > 
> > There are cases where the PCIe device would be physically connected to the
> > bus, but the device firmware might not be active. So the LTSSM will
> > get stuck in POLL.{Active/Compliance} states.
> > 
> > This behavior is common with endpoint devices controlled by the PCI
> > Endpoint framework, where the device will wait for the user to start its
> > operation through configfs.
> > 
> > For those cases, print the relevant log and return -EIO to indicate that
> > the device is present, but not active. This will allow the callers to skip
> > the failure as the device might become active in the future.
> > 
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
> > ---
> >  drivers/pci/controller/dwc/pcie-designware.c | 15 +++++++++++++--
> >  1 file changed, 13 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> > index 55c1c60f7f8f..aca5bbeade03 100644
> > --- a/drivers/pci/controller/dwc/pcie-designware.c
> > +++ b/drivers/pci/controller/dwc/pcie-designware.c
> > @@ -696,8 +696,9 @@ void dw_pcie_disable_atu(struct dw_pcie *pci, u32 dir, int index)
> >   * 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.
> > + * Returns: 0 if link is up, -ENODEV if device is not found, -EIO if the device
> > + * is found but not active and -ETIMEDOUT if the link fails to come up for other
> > + * reasons.
> >   */
> >  int dw_pcie_wait_for_link(struct dw_pcie *pci)
> >  {
> > @@ -722,6 +723,16 @@ int dw_pcie_wait_for_link(struct dw_pcie *pci)
> >  		    ltssm == DW_PCIE_LTSSM_DETECT_ACT) {
> >  			dev_info(pci->dev, "Device not found\n");
> >  			return -ENODEV;
> > +
> > +		/*
> > +		 * If the link is in POLL.{Active/Compliance} state, then the
> > +		 * device is found to be connected to the bus, but it is not
> > +		 * active i.e., the device firmware might not yet initialized.
> > +		 */
> > +		} else if (ltssm == DW_PCIE_LTSSM_POLL_ACTIVE ||
> > +			   ltssm == DW_PCIE_LTSSM_POLL_COMPLIANCE) {
> > +			dev_info(pci->dev, "Device found, but not active\n");
> > +			return -EIO;
> >  		}
> >  
> >  		dev_info(pci->dev, "Phy link never came up\n");
> 
> This should probably be squashed with the previous patch.
> 

No. I'd like to keep it as a separate patch because I think this deserves its
own justification.

- Mani

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