On Mon, Jul 13, 2020 at 10:27:47AM +0200, Pali Rohár wrote: > On Friday 10 July 2020 10:18:00 Lorenzo Pieralisi wrote: > > On Thu, Jul 09, 2020 at 05:09:59PM +0200, Pali Rohár wrote: > > > > I understand that but the bridge bus resource can be trimmed to just > > > > contain the root bus because that's the only one where there is a > > > > chance you can enumerate a device. > > > > > > It is possible to register only root bridge without endpoint? > > > > It is possible to register the root bridge with a trimmed IORESOURCE_BUS > > so that you don't enumerate anything other than the root port. > > Hello Lorenzo! I really do not know how to achieve it. From code it > looks like that pci/probe.c scans child buses unconditionally. > > pci-aardvark.c calls pci_host_probe() which calls functions > pci_scan_root_bus_bridge() which calls pci_scan_child_bus() which calls > pci_scan_child_bus_extend() which calls pci_scan_bridge_extend() (bridge > needs to be reconfigured) which then try to probe child bus via > pci_scan_child_bus_extend() because bridge is not card bus. > > In function pci_scan_bridge_extend() I do not see a way how to skip > probing for child buses which would avoid enumerating aardvark root > bridge when PCIe device is not connected. > > dmesg output contains: > > advk-pcie d0070000.pcie: link never came up > advk-pcie d0070000.pcie: PCI host bridge to bus 0000:00 > pci_bus 0000:00: root bus resource [bus 00-ff] This resource can be limited to the root bus number only before calling pci_host_probe() (ie see pci_parse_request_of_pci_ranges() and code in pci_scan_bridge_extend() that programs primary/secondary/subordinate busses) but I think that only papers over the issue, it does not fix it. I will go over the thread again but I suspect I can merge the patch even though I still believe there is work to be done to understand the issue we are facing. Lorenzo > pci_bus 0000:00: root bus resource [mem 0xe8000000-0xe8ffffff] > pci_bus 0000:00: root bus resource [io 0x0000-0xffff] (bus address [0xe9000000-0xe900ffff]) > pci_bus 0000:00: scanning bus > pci 0000:00:00.0: [1b4b:0100] type 01 class 0x060400 > pci 0000:00:00.0: reg 0x38: [mem 0x00000000-0x000007ff pref] > pci_bus 0000:00: fixups for bus > pci 0000:00:00.0: scanning [bus 00-00] behind bridge, pass 0 > pci 0000:00:00.0: bridge configuration invalid ([bus 00-00]), reconfiguring > pci 0000:00:00.0: scanning [bus 00-00] behind bridge, pass 1 > pci_bus 0000:01: scanning bus > advk-pcie d0070000.pcie: advk_pcie_valid_device
