On Mon, Nov 11, 2024 at 02:11:51PM +0530, Krishna chaitanya chundru wrote: > 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. > > So enable runtime pm of the host bridge device, so that dependency > chain in maintained between endpoint devices and the controller driver. > > PM framework expectes parent runtime pm enabled before enabling runtime > pm of the child. As PCIe starfive device is enabling runtime pm after > the pci_host_probe which enables runtime pm of the child device i.e for > the bridge device a warning is shown saying "pcie-starfive 940000000.pcie: > Enabling runtime PM for inactive device with active children" and also > shows possible circular locking dependency detected message. > > As it is must to enable parent device's runtime PM before enabling child's > runtime pm as the pcie-starfive device runtime pm is enabled after child > runtime starfive device is seeing the warning. > > In the first patch fix the pcie-starfive driver by enabling runtime > pm before calling pci_host_probe(). > > All other PCIe controller drivers are enabling runtime pm before > calling pci_host_probe() which is as expected so don't require any > fix like pcie-starfive driver. > > Signed-off-by: Krishna chaitanya chundru <quic_krichai@xxxxxxxxxxx> Provisionally applied to pci/pm for v6.13. I see a typo or two, so the commit logs will likely be updated, but I pushed the branch to get build testing started. > --- > Changes in v7: > - Bring the cover letter details to commit message as suggested by bjorn. > - Add a comment in the driver to ensure pm_runtime_enable is called > before host bridge pm_runtime_enable(). > - Link to v6: https://lore.kernel.org/r/20241017-runtime_pm-v6-0-55eab5c2c940@xxxxxxxxxxx > Changes in v6: > - include the patch by mayank which fixes runtime pm enable order for > pcie starfive driver. > Changes in v5: > - call pm_runtime_no_callbacks() as suggested by Rafael. > - include the commit texts as suggested by Rafael. > - Link to v4: https://lore.kernel.org/linux-pci/20240708-runtime_pm-v4-1-c02a3663243b@xxxxxxxxxxx/ > 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 > > --- > Krishna chaitanya chundru (1): > PCI: Enable runtime pm of the host bridge > > Mayank Rana (1): > PCI: starfive: Enable PCIe controller's runtime PM before probing host bridge > > drivers/pci/controller/plda/pcie-starfive.c | 10 +++++++--- > drivers/pci/probe.c | 11 +++++++++++ > 2 files changed, 18 insertions(+), 3 deletions(-) > --- > base-commit: 2f87d0916ce0d2925cedbc9e8f5d6291ba2ac7b2 > change-id: 20241016-runtime_pm-d3dbf41736b6 > > Best regards, > -- > Krishna chaitanya chundru <quic_krichai@xxxxxxxxxxx> >
