On Sat, Mar 21, 2020 at 11:20:07AM +0100, Rafael J. Wysocki wrote: > On Sat, Mar 21, 2020 at 5:55 AM Saravana Kannan <saravanak@xxxxxxxxxx> wrote: > > > > Sometimes, more than one (generally two) device can point to the same > > fwnode. However, only one device is set as the fwnode's device > > (fwnode->dev) and can be looked up from the fwnode. > > > > Typically, only one of these devices actually have a driver and actually > > probe. If we create device links for all these devices, then the > > suppliers' of these devices (with the same fwnode) will never get a > > sync_state() call because one of their consumer devices will never probe > > (because they don't have a driver). > > > > So, create device links only for the device that is considered as the > > fwnode's device. > > > > One such example of this is the PCI bridge platform_device and the > > corresponding pci_bus device. Both these devices will have the same > > fwnode. It's the platform_device that is registered first and is set as > > the fwnode's device. Also the platform_device is the one that actually > > probes. Without this patch none of the suppliers of a PCI bridge > > platform_device would get a sync_state() callback. > > For the record, I think that this is a PCI subsystem problem, but I > agree with the patch here. I don't understand the issue here. Can somebody educate me? I'm guessing this is related to pci_set_bus_of_node(), which does (for PCI-to-PCI bridges): bus->dev.of_node = of_node_get(bus->self->dev.of_node); bus->dev.fwnode = &bus->dev.of_node->fwnode; where "bus" points to a struct pci_bus and "bus->self" points to the struct pci_dev for the bridge leading to the bus? Is this related to the fact that we have a struct device for both a PCI-to-PCI bridge and for its downstream bus? Any suggestions for how could we fix this problem in the PCI subsystem?
