Re: [PATCH v2] PCI: cadence: skip the link polling when endpoint not connected

[Manivannan Sadhasivam]

On Tue, Jun 23, 2026 at 03:21:48PM +0530, Aksh Garg wrote:
> cdns_pcie_host_wait_for_link() polls on link-up for 10 retries with a
> delay of 90-100ms each (~1 second). A call to cdns_pcie_host_link_setup()
> during the resume operation blocks the resume operation unnecessarily for
> ~1s even when no endpoint device is connected.
> 
> Add link_down_no_hotplug flag to track link state across suspend/resume
> cycles (for the platforms that do not support hotplug). If link was
> down before suspend in such platforms, skip the expensive polling in
> resume since no endpoint was present.
> 
> Reviewed-by: Chen Wang <unicorn_wang@xxxxxxxxxxx>
> Reviewed-by: Siddharth Vadapalli <s-vadapalli@xxxxxx>
> Signed-off-by: Aksh Garg <a-garg7@xxxxxx>
> ---
> 
> Changes from v1 to v2:
> - Updated the flag name from 'skip_link_polling' to 'link_down_no_hotplug'
> 
> v1: https://lore.kernel.org/all/20260605071922.1724499-1-a-garg7@xxxxxx/
> 
>  drivers/pci/controller/cadence/pci-j721e.c             | 5 +++++
>  drivers/pci/controller/cadence/pcie-cadence-host-hpa.c | 3 +++
>  drivers/pci/controller/cadence/pcie-cadence-host.c     | 3 +++
>  drivers/pci/controller/cadence/pcie-cadence.h          | 3 +++
>  4 files changed, 14 insertions(+)
> 
> diff --git a/drivers/pci/controller/cadence/pci-j721e.c b/drivers/pci/controller/cadence/pci-j721e.c
> index bfdfe98d5aba..48db7a6cf754 100644
> --- a/drivers/pci/controller/cadence/pci-j721e.c
> +++ b/drivers/pci/controller/cadence/pci-j721e.c
> @@ -686,6 +686,11 @@ static int j721e_pcie_suspend_noirq(struct device *dev)
>  	struct j721e_pcie *pcie = dev_get_drvdata(dev);
>  
>  	if (pcie->mode == PCI_MODE_RC) {
> +		struct cdns_pcie_rc *rc = cdns_pcie_to_rc(pcie->cdns_pcie);
> +
> +		/* If link is down before suspend, skip polling in resume */
> +		rc->link_down_no_hotplug = !j721e_pcie_link_up(pcie->cdns_pcie);
> +
>  		gpiod_set_value_cansleep(pcie->reset_gpio, 0);
>  		clk_disable_unprepare(pcie->refclk);
>  	}
> diff --git a/drivers/pci/controller/cadence/pcie-cadence-host-hpa.c b/drivers/pci/controller/cadence/pcie-cadence-host-hpa.c
> index 0f540bed58e8..31cf50cff8f8 100644
> --- a/drivers/pci/controller/cadence/pcie-cadence-host-hpa.c
> +++ b/drivers/pci/controller/cadence/pcie-cadence-host-hpa.c
> @@ -301,6 +301,9 @@ int cdns_pcie_hpa_host_link_setup(struct cdns_pcie_rc *rc)
>  		return ret;
>  	}
>  
> +	if (rc->link_down_no_hotplug)
> +		return 0;
> +
>  	ret = cdns_pcie_host_wait_for_link(pcie, cdns_pcie_hpa_link_up);
>  	if (ret)
>  		dev_dbg(dev, "PCIe link never came up\n");
> diff --git a/drivers/pci/controller/cadence/pcie-cadence-host.c b/drivers/pci/controller/cadence/pcie-cadence-host.c
> index 0bc9e6e90e0e..50abc657a871 100644
> --- a/drivers/pci/controller/cadence/pcie-cadence-host.c
> +++ b/drivers/pci/controller/cadence/pcie-cadence-host.c
> @@ -352,6 +352,9 @@ int cdns_pcie_host_link_setup(struct cdns_pcie_rc *rc)
>  		return ret;
>  	}
>  
> +	if (rc->link_down_no_hotplug)
> +		return 0;
> +
>  	ret = cdns_pcie_host_start_link(rc, cdns_pcie_link_up);
>  	if (ret)
>  		dev_dbg(dev, "PCIe link never came up\n");
> diff --git a/drivers/pci/controller/cadence/pcie-cadence.h b/drivers/pci/controller/cadence/pcie-cadence.h
> index 574e9cf4d003..1561022c1a8b 100644
> --- a/drivers/pci/controller/cadence/pcie-cadence.h
> +++ b/drivers/pci/controller/cadence/pcie-cadence.h
> @@ -117,6 +117,8 @@ struct cdns_pcie {
>   * @no_inbound_map: Whether inbound mapping is supported
>   * @quirk_broken_aspm_l0s: Disable ASPM L0s support as quirk
>   * @quirk_broken_aspm_l1: Disable ASPM L1 support as quirk
> + * @link_down_no_hotplug: Skip link polling during resume on no-hotplug
> + *			  platforms when link was down before suspend
>   */
>  struct cdns_pcie_rc {
>  	struct cdns_pcie	pcie;
> @@ -131,6 +133,7 @@ struct cdns_pcie_rc {
>  	unsigned int            no_inbound_map:1;
>  	unsigned int            quirk_broken_aspm_l0s:1;
>  	unsigned int            quirk_broken_aspm_l1:1;
> +	unsigned int		link_down_no_hotplug:1;

If the goal of this flag is to convey the information that the platform doesn't
support hotplug, then it should be called 'no_hotplug'. Skipping the polling
during LDn is the usecase.

- Mani

-- 
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