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

[Aksh Garg]

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().

> 
>>           gpiod_set_value_cansleep(pcie->reset_gpio, 0);
>>           clk_disable_unprepare(pcie->refclk);
>>       }
> 
> [TRIMMED]
> 
> Regards,
> Siddharth.