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

[Neil Armstrong]

Hi,

On 10/16/26 13:08, Krishna Chaitanya Chundru wrote:
> 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@xxxxxxxxxxxxxxxx

Thanks this fixes the issue,

Neil

> > Neil
> >
> > > Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@xxxxxxxxxxxxxxxx>
> > > ---
> > >    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,