On 2013/4/26 14:20, Yinghai Lu wrote: > On Thu, Apr 25, 2013 at 9:02 PM, Yijing Wang <wangyijing@xxxxxxxxxx> wrote: >> Hi Yinghai, >> We should not remove this additional pci_disable_device(). >> Because we enable pcie port device twice before. The first is pci_enable_brides(), >> in x86, it was called in pci_assign_unassigned_resources(). The second in pcie_port_device_register(). >> So we should call pci_disable_device() twice for pci_dev->enable_cnt balance. >> >> But there is still a problem here. If we unbind a pcie port device pcie port driver, we can not >> use its child devices again, because this pcie port device was disabled absolutely. >> >> So I think we should move the second pci_disable_device() to remove.c. >> >> I sent this patch to Bjorn and following is Bjorn reply >> "And it's not clear to me whether unbinding the >> pcie port driver should disable the bridge at all. I think one could >> argue that the bridge should remain functional even if the driver is >> unloaded, because the PCI core *enables* the bridge even if the driver >> is never loaded." >> >> Yinghai, how do you think about this issue? > Hi Yinghai, Thanks for your comment! We enable_bridges in PCI core code, so I think we should disable device in remove.c(PCI core level), another reason is call second pci_disable_device() in pci_stop_bus_device() is safe, because all child device has been stopped(unbind driver already). > 1. we always enable bridges after assign unassigned resource for boot path > and hotplug path. > we should never call disable for that. I agree "we should never call second disable" unless we stop this sub pci-tree(). Maybe the attached patch last letter is not safe enough, should wait pci bridge complete to stop itself, then call the second pci_disable_device(). > > 2. driver should be keep enable/disable during probe/remove I agree, use enable/disable balance is better. > > looks like we need to rethink pci enable bridge. > > if we want to enable one pci device, we should go up to enable all bridges till > root. Yes, now we enable pci bridges from root to end. like in pci_assign_unassigned_resources(). > > let if we disable one pci device, we need to go up to disable bridge if its all > pci device children get disabled. Yes, This is what I think too. It seems like we only can do this in remove.c > > if there is pci driver is bound with bridge device, those > disable/enable bridge should be skipped. Hmm, currently system achieve this by checking pci_dev->enable_cnt. > > Thanks > > Yinghai > > . > -- Thanks! Yijing -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
