On Mon, Jul 08, 2024 at 10:19:40AM +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. > > 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. > > So enable runtime PM for the host bridge, so that controller driver > goes to suspend only when all child devices goes to runtime suspend. > > Signed-off-by: Krishna chaitanya chundru <quic_krichai@xxxxxxxxxxx> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx> Note to the maintainers: This patch should be applied at the start of the RC window to give enough testing in linux-next since it touches the PM of all host bridges. - Mani > --- > Changes in v4: > - Changed pm_runtime_enable() to devm_pm_runtime_enable() (suggested by mayank) > - Link to v3: https://lore.kernel.org/lkml/20240609-runtime_pm-v3-1-3d0460b49d60@xxxxxxxxxxx/ > Changes in v3: > - Moved the runtime API call's from the dwc driver to PCI framework > as it is applicable for all (suggested by mani) > - Updated the commit message. > - Link to v2: https://lore.kernel.org/all/20240305-runtime_pm_enable-v2-1-a849b74091d1@xxxxxxxxxxx > Changes in v2: > - Updated commit message as suggested by mani. > - Link to v1: https://lore.kernel.org/r/20240219-runtime_pm_enable-v1-1-d39660310504@xxxxxxxxxxx > --- > > --- > drivers/pci/probe.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c > index 8e696e547565..fd49563a44d9 100644 > --- a/drivers/pci/probe.c > +++ b/drivers/pci/probe.c > @@ -3096,6 +3096,10 @@ int pci_host_probe(struct pci_host_bridge *bridge) > } > > pci_bus_add_devices(bus); > + > + pm_runtime_set_active(&bridge->dev); > + devm_pm_runtime_enable(&bridge->dev); > + > return 0; > } > EXPORT_SYMBOL_GPL(pci_host_probe); > > --- > base-commit: 1613e604df0cd359cf2a7fbd9be7a0bcfacfabd0 > change-id: 20240708-runtime_pm-978ccbca6130 > > Best regards, > -- > Krishna chaitanya chundru <quic_krichai@xxxxxxxxxxx> > -- மணிவண்ணன் சதாசிவம்
