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

[Manikandan Karunakaran Pillai]

>-----Original Message-----
>From: Siddharth Vadapalli <s-vadapalli at ti.com>
>Sent: Tuesday, June 9, 2026 10:42 AM
>To: Aksh Garg <a-garg7 at ti.com>
>Cc: s-vadapalli at ti.com; vigneshr at ti.com; lpieralisi at kernel.org;
>kwilczynski at kernel.org; mani at kernel.org; robh at kernel.org;
>bhelgaas at google.com; Manikandan Karunakaran Pillai
><mpillai at cadence.com>; unicorn_wang at outlook.com; me at ziyao.cc;
>18255117159 at 163.com; linux-pci at vger.kernel.org; linux-arm-
>kernel at lists.infradead.org; linux-kernel at vger.kernel.org; danishanwar at ti.com
>Subject: Re: [PATCH] PCI: cadence: skip the link polling when endpoint not
>connected
>
>EXTERNAL MAIL
>
>
>On 09/06/26 09:58, Aksh Garg wrote:
>>
>>
>> On 09/06/26 09:12, Siddharth Vadapalli wrote:
>>> On 05/06/26 12:49, 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 skip_link_polling flag to track link state across suspend/resume
>>>> cycles. If link was down before suspend, skip the expensive polling
>>>> in resume since no endpoint was present.
>>>>
>>>> Signed-off-by: Aksh Garg <a-garg7 at ti.com>
>>>> ---
>>>>   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..849eb8bb9e45 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->skip_link_polling = !j721e_pcie_link_up(pcie->cdns_pcie);
>>>> +
>>>
>>> Please consider the following scenario:
>>> 1. Endpoint device is not connected initially and we suspend with
>>> 'skip_link_polling' set to true.
>>> 2. We resume and skip link polling.
>>> 3. An Endpoint device is connected to the PCIe Connector a while later.
>>> 4. We perform a bus rescan, but with skip_link_polling still set (in
>>> resume), wouldn't we skip polling for the link to be up?
>>>
>>> Shouldn't 'skip_link_polling' be set to false on resume, after we skip
>>> the polling initially, in order to allow waiting for a link up for a
>>> newly connected device? Although this may not be done in practice and the
>>> Endpoint device may always be left connected from the start, I am
>>> wondering if we should clear 'skip_link_polling' on resume to account for
>>> the aforementioned scenario. Let me know if I am overlooking something
>here.
>>
>> This path is not used during bus rescan. This implies that during the
>> rescan, we do not call cdns_pcie_host_link_setup() or
>> cdns_pcie_hpa_host_link_setup().
>Thank you for clarifying.
>
>Reviewed-by: Siddharth Vadapalli <s-vadapalli at ti.com>
>

Looks good to me


>Regards,
>Siddharth.