On Tue, Jan 14, 2025 at 03:16:53PM -0600, Bjorn Helgaas wrote: > On Mon, Jan 13, 2025 at 09:55:49PM +0530, Manivannan Sadhasivam wrote: > > On Tue, Jan 07, 2025 at 03:27:59PM +0100, Johan Hovold wrote: > > > On Tue, Jan 07, 2025 at 07:40:39PM +0530, Krishna Chaitanya Chundru wrote: > > > > On 1/7/2025 6:49 PM, Johan Hovold wrote: > > > > > > > >> @@ -3106,6 +3106,17 @@ int pci_host_probe(struct pci_host_bridge *bridge) > > > > >> pcie_bus_configure_settings(child); > > > > >> > > > > >> pci_bus_add_devices(bus); > > > > >> + > > > > >> + /* > > > > >> + * Ensure pm_runtime_enable() is called for the controller drivers, > > > > >> + * before calling pci_host_probe() as pm frameworks expects if the > > > > >> + * parent device supports runtime pm then it needs to enabled before > > > > >> + * child runtime pm. > > > > >> + */ > > > > >> + pm_runtime_set_active(&bridge->dev); > > > > >> + pm_runtime_no_callbacks(&bridge->dev); > > > > >> + devm_pm_runtime_enable(&bridge->dev); > > > > >> + > > > > >> return 0; > > > > >> } > > > > >> EXPORT_SYMBOL_GPL(pci_host_probe); > > > > > > > > > > I just noticed that this change in 6.13-rc1 is causing the > > > > > following warning on resume from suspend on machines like the > > > > > Lenovo ThinkPad X13s: > > > > > > > Can you confirm if you are seeing this issue is seen in the > > > > boot-up case also. As this part of the code executes only at the > > > > boot time and will not have effect in resume from suspend. > > > > > > No, I only see it during resume. And enabling runtime PM can (and > > > in this case, obviously does) impact system suspend as well. > > > > > > > > pci0004:00: pcie4: Enabling runtime PM for inactive device with active children > > > > > > > I believe this is not causing any functional issues. > > > > > > It still needs to be fixed. > > > > > > > > which may have unpopulated ports (this laptop SKU does not > > > > > have a modem). > > > > > > > Can you confirm if this warning goes away if there is some > > > > endpoint connected to it. > > > > > > I don't have anything to connect to the slot in this machine, but > > > this seems to be the case as I do not see this warning for the > > > populated slots, nor on the CRD reference design which has a modem > > > on PCIe4. > > > > Yes, this is only happening for unpopulated slots and the warning > > shows up only if runtime PM is enabled for both PCI bridge and host > > bridge. This patch enables the runtime PM for host bridge and if the > > PCI bridge runtime PM is also enabled (only happens now for > > ACPI/BIOS based platforms), then the warning shows up only if the > > PCI bridge was RPM suspended (mostly happens if there was no device > > connected) during the system wide resume time. > > > > For the sake of reference, PCI host bridge is the parent of PCI > > bridge. > > > > Looking at where the warning gets triggered (in > > pm_runtime_enable()), we have the below checks: > > > > dev->power.runtime_status == RPM_SUSPENDED > > !dev->power.ignore_children > > atomic_read(&dev->power.child_count) > 0 > > > > When pm_runtime_enable() gets called for PCI host bridge: > > > > dev->power.runtime_status = RPM_SUSPENDED > > dev->power.ignore_children = 0 > > dev->power.child_count = 1 > > > > First 2 passes seem legit, but the issue is with the 3rd one. Here, > > the child_count of 1 means that the PCI host bridge has an 'active' > > child (which is the PCI bridge). The PCI bridge was supposed to be > > RPM_SUSPENDED as the resume process should first resume the parent > > (PCI host bridge). But this is not the case here. > > > > Then looking at where the child_count gets incremented, it leads to > > pm_runtime_set_active() of device_resume_noirq(). > > pm_runtime_set_active() is only called for a device if > > dev_pm_skip_suspend() succeeds, which requires > > DPM_FLAG_SMART_SUSPEND flag to be set and the device to be runtime > > suspended. > > > > This criteria matches for PCI bridge. So its status was set to > > 'RPM_ACTIVE' even though the parent PCI host bridge was still in the > > RPM_SUSPENDED state. I don't think this is a valid condition as seen > > from the warning triggered for PCI host bridge when > > pm_runtime_enable() is called from device_resume_early(): > > > > pci0004:00: pcie4: Enabling runtime PM for inactive device with > > active children > > > > I'm not sure of what the fix is in this case. But removing the > > DPM_FLAG_SMART_SUSPEND flag from PCI bridge driver (portdrv) makes > > the warning go away. This indicates that something is wrong with the > > DPM_FLAG_SMART_SUSPEND flag handling in PM core. > > > > Ulf/Rafael, thoughts? > > What's the plan for this? Does anybody have a proposal? > TBH, I don't know how to fix this issue in a proper way. I need inputs from Rafael/Ulf. > IIUC there is no functional issue, but the new warning must be fixed, > and it would sure be nice to do it before v6.13. If there *is* a > functional problem, we need to consider a revert ASAP. > There is no functional problem that I'm aware of, so revert is not warranted. - Mani -- மணிவண்ணன் சதாசிவம்
