Thu, Oct 03, 2024 at 05:10:33PM -0500, Bjorn Helgaas kirjoitti: > On Thu, Oct 03, 2024 at 11:32:32AM +0530, Krishna chaitanya chundru wrote: > > The Controller driver is the parent device of the PCIe host bridge, > > PCI-PCI bridge and PCIe endpoint as shown below. > > > > PCIe controller(Top level parent & parent of host bridge) > > | > > v > > PCIe Host bridge(Parent of PCI-PCI bridge) > > | > > v > > PCI-PCI bridge(Parent of endpoint driver) > > | > > v > > PCIe endpoint driver > > > > Now, when the controller device goes to runtime suspend, PM framework > > will check the runtime PM state of the child device (host bridge) and > > will find it to be disabled. So it will allow the parent (controller > > device) to go to runtime suspend. Only if the child device's state was > > 'active' it will prevent the parent to get suspended. > > > > It is a property of the runtime PM framework that it can only > > follow continuous dependency chains. That is, if there is a device > > with runtime PM disabled in a dependency chain, runtime PM cannot be > > enabled for devices below it and above it in that chain both at the > > same time. > > > > Since runtime PM is disabled for host bridge, the state of the child > > devices under the host bridge is not taken into account by PM framework > > for the top level parent, PCIe controller. So PM framework, allows > > the controller driver to enter runtime PM irrespective of the state > > of the devices under the host bridge. And this causes the topology > > breakage and also possible PM issues like controller driver goes to > > runtime suspend while endpoint driver is doing some transfers. > > > > Because of the above, in order to enable runtime PM for a PCIe > > controller device, one needs to ensure that runtime PM is enabled for > > all devices in every dependency chain between it and any PCIe endpoint > > (as runtime PM is enabled for PCIe endpoints). > > > > This means that runtime PM needs to be enabled for the host bridge > > device, which is present in all of these dependency chains. > > > > After this change, the host bridge device will be runtime-suspended > > by the runtime PM framework automatically after suspending its last > > child and it will be runtime-resumed automatically before resuming its > > first child which will allow the runtime PM framework to track > > dependencies between the host bridge device and all of its > > descendants. > > Applied to pci/pm for v6.13, thanks for your patience is working > through this! ... > > + pm_runtime_set_active(&bridge->dev); > > + pm_runtime_no_callbacks(&bridge->dev); > > + devm_pm_runtime_enable(&bridge->dev); So, potentially this might lead to a case where PM runtime is enabled and won't be disabled on the bridge device removal. Is this a problem? TL;DR: I have found no explanations why error code from devm_*() call is being ignored. > > return 0; -- With Best Regards, Andy Shevchenko
