Hi, a gentle ping...will it be considered for this window? Thanks. On 2022/6/6 21:00, Yicong Yang wrote: > A bridge in a non-D0 power state does not forward config accesses to > its secondary side (PCIe r6.0, sec 5.3.1). Make sure the bridge is > in D0 while we enumerate devices below it. > > The case can be produced when the bridge is runtime-suspended (either > in D3hot or D3cold) like below: > > $ echo 1 > /sys/bus/pci/devices/0000:80:00.0/0000:81:00.1/remove > $ echo 1 > /sys/bus/pci/devices/0000:80:00.0/pci_bus/0000:81/rescan > > 0000:80:00.0 is a Root Port and it is runtime-suspended, so the > configuration space of 0000:81:00.1 is unreachable in rescan > and the device cannot be enumerated. > > Power up the bridge when scanning the child bus and allow it to > suspend again by adding pm_runtime_get_sync()/pm_runtime_put() > in pci_scan_child_bus_extend(). > > Cc: Rafael J. Wysocki <rafael@xxxxxxxxxx> > Cc: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> > Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> > Signed-off-by: Yicong Yang <yangyicong@xxxxxxxxxxxxx> > Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > --- > Change since v5: > - Tweak the commit message suggested by Bjorn > Link: https://lore.kernel.org/linux-pci/20220525141930.GA290827@bhelgaas/ > > Change since v4: > - rephrase the commit suggested by Rafael > Link: https://lore.kernel.org/lkml/20220422080404.27724-1-yangyicong@xxxxxxxxxxxxx/ > > Change since v3: > - retain the pm_runtime_*() calls in pci_scan_bridge_extend() as Rafael points > out that it's necessary when the brigde is in D3cold > Link: https://lore.kernel.org/linux-pci/20220414123736.34150-1-yangyicong@xxxxxxxxxxxxx/ > > Change since v2: > - just rebase it on v5.18-rc2 > Link: https://lore.kernel.org/linux-pci/1601029386-4928-1-git-send-email-yangyicong@xxxxxxxxxxxxx/ > > Change since v1: > - use an intermediate variable *bridge as suggested > - remove the pm_runtime_*() calls in pci_scan_bridge_extend() > Link: https://lore.kernel.org/linux-pci/1596022223-4765-1-git-send-email-yangyicong@xxxxxxxxxxxxx/ > > drivers/pci/probe.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c > index 17a969942d37..b108e72b6586 100644 > --- a/drivers/pci/probe.c > +++ b/drivers/pci/probe.c > @@ -2859,11 +2859,20 @@ static unsigned int pci_scan_child_bus_extend(struct pci_bus *bus, > unsigned int used_buses, normal_bridges = 0, hotplug_bridges = 0; > unsigned int start = bus->busn_res.start; > unsigned int devfn, fn, cmax, max = start; > + struct pci_dev *bridge = bus->self; > struct pci_dev *dev; > int nr_devs; > > dev_dbg(&bus->dev, "scanning bus\n"); > > + /* > + * Make sure the bus bridge is powered on, otherwise we may not be > + * able to scan the devices as we may fail to access the configuration > + * space of subordinates. > + */ > + if (bridge) > + pm_runtime_get_sync(&bridge->dev); > + > /* Go find them, Rover! */ > for (devfn = 0; devfn < 256; devfn += 8) { > nr_devs = pci_scan_slot(bus, devfn); > @@ -2976,6 +2985,9 @@ static unsigned int pci_scan_child_bus_extend(struct pci_bus *bus, > } > } > > + if (bridge) > + pm_runtime_put(&bridge->dev); > + > /* > * We've scanned the bus and so we know all about what's on > * the other side of any bridges that may be on this bus plus >
