Hi Bjorn, Alex, Lukas, Is this acceptable or anything needs to be improved? Thanks windy On Tue, May 24, 2022 at 1:15 AM Sheng Bi <windy.bi.enflame@xxxxxxxxx> wrote: > > pci_bridge_secondary_bus_reset() triggers SBR followed by 1 second sleep, > and then uses pci_dev_wait() for waiting device ready. The dev parameter > passes to the wait function is currently the bridge itself, but not the > device been reset. > > If we call pci_bridge_secondary_bus_reset() to trigger SBR to a device, > there is 1 second sleep but not waiting device ready, since the bridge > is always ready while resetting downstream devices. pci_dev_wait() here > is a no-op actually. This would be risky in the case which the device > becomes ready after more than 1 second, especially while hotplug enabled. > The late coming hotplug event after 1 second will trigger hotplug module > to remove/re-insert the device. > > Instead of waiting ready of bridge itself, changing to wait all the > downstream devices become ready with timeout PCIE_RESET_READY_POLL_MS > after SBR, considering all downstream devices are affected during SBR. > Once one of the devices doesn't reappear within the timeout, return > -ENOTTY to indicate SBR doesn't complete successfully. > > Fixes: 6b2f1351af56 ("PCI: Wait for device to become ready after secondary bus reset") > Signed-off-by: Sheng Bi <windy.bi.enflame@xxxxxxxxx> > --- > drivers/pci/pci.c | 30 +++++++++++++++++++++++++++++- > 1 file changed, 29 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index eb7c0a08ff57..4653a9ae6e5b 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -5049,6 +5049,34 @@ void pci_bridge_wait_for_secondary_bus(struct pci_dev *dev) > } > } > > +static int pci_bridge_secondary_bus_wait(struct pci_dev *bridge, int timeout) > +{ > + struct pci_dev *dev; > + unsigned long start_jiffies; > + > + down_read(&pci_bus_sem); > + > + if (!bridge->subordinate || list_empty(&bridge->subordinate->devices)) { > + up_read(&pci_bus_sem); > + return 0; > + } > + > + list_for_each_entry(dev, &bridge->subordinate->devices, bus_list) { > + start_jiffies = jiffies; > + > + if (timeout < 0 || pci_dev_wait(dev, "bus reset", timeout)) { > + up_read(&pci_bus_sem); > + return -ENOTTY; > + } > + > + timeout -= jiffies_to_msecs(jiffies - start_jiffies); > + } > + > + up_read(&pci_bus_sem); > + > + return 0; > +} > + > void pci_reset_secondary_bus(struct pci_dev *dev) > { > u16 ctrl; > @@ -5092,7 +5120,7 @@ int pci_bridge_secondary_bus_reset(struct pci_dev *dev) > { > pcibios_reset_secondary_bus(dev); > > - return pci_dev_wait(dev, "bus reset", PCIE_RESET_READY_POLL_MS); > + return pci_bridge_secondary_bus_wait(dev, PCIE_RESET_READY_POLL_MS); > } > EXPORT_SYMBOL_GPL(pci_bridge_secondary_bus_reset); > > > base-commit: 617c8a1e527fadaaec3ba5bafceae7a922ebef7e > -- > 2.36.1 >