Re: [PATCH] PCI: qcom: Advertise hotplug with no command completion support

[Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>]

On 10/16/2026 3:54 PM, Neil Armstrong wrote:
> Hi,
>
> On 3/14/26 02:56, Krishna Chaitanya Chundru wrote:
>> QCOM PCIe controller advertise hotplug capability in hardware but do not
>> support hotplug command completion. As a result, the PCI core registers
>> the pciehp service and issues hotplug commands that never gets completions,
>> leading to repeated timeout warnings and multi-second delays during boot
>> and suspend/resume.
>>
>> Commit a54db86ddc153 ("PCI: qcom: Do not advertise hotplug capability for
>> IPs v2.7.0 and v1.9.0") avoided these timeouts by clearing the Hot-Plug
>> Capability bit entirely, which also disabled all hotplug functionality.
>>
>> Instead of disabling hotplug, mark these controllers as not supporting
>> command completion by setting the No Command Completed Support (NCCS) bit
>> in the Slot Capabilities register. This prevents the PCI hotplug driver
>> from waiting for commands completion while still allowing hotplug-related
>> functionality such as Data Link Layer state change events.
>
> I'm a little late to the party, but marking the RC as Hotplus means the bridge
> is marked as is_pciehp and pci_bridge_d3_possible() returns false.
>
> This means this breaks D3Cold support completely since in
> __pci_host_common_d3cold_possible()
> we now check all PCI devices, including bridges, and the RC is not set in
> D3Hot anymore.
>
> The only way to enable D3Cold is to pass pcie_port_pm=force to allow D3 on all
> Hotplug bridges. Which may be wrong on TB bridges.
>
Hi Neil,
can you enable hotplug driver and use this patch [1], that should solve the issue.

[1]
https://patch.msgid.link/20260729165005.896725-1-manivannan.sadhasivam@oss.qualcomm.com

> Neil
>
>>
>> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
>> ---
>>   drivers/pci/controller/dwc/pcie-qcom.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c
>> b/drivers/pci/controller/dwc/pcie-qcom.c
>> index
>> 67a16af69ddc75fca1b123e70715e692a91a9135..a2924610f3625f2456a491473c135840e31bafb9
>> 100644
>> --- a/drivers/pci/controller/dwc/pcie-qcom.c
>> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
>> @@ -358,7 +358,7 @@ static void qcom_pcie_clear_hpc(struct dw_pcie *pci)
>>       dw_pcie_dbi_ro_wr_en(pci);
>>         val = readl(pci->dbi_base + offset + PCI_EXP_SLTCAP);
>> -    val &= ~PCI_EXP_SLTCAP_HPC;
>> +    val |= PCI_EXP_SLTCAP_NCCS;
>>       writel(val, pci->dbi_base + offset + PCI_EXP_SLTCAP);
>>         dw_pcie_dbi_ro_wr_dis(pci);
>>
>> ---
>> base-commit: 0257f64bdac7fdca30fa3cae0df8b9ecbec7733a
>> change-id: 20260313-hotplug-4c296595b5b8
>>
>> Best regards,
>