Re: [PATCHv3 2/4] drivers/base: utilize device tree info to shutdown devices

From: Lukas Wunner
Date: Tue Jul 03 2018 - 03:51:15 EST

On Tue, Jul 03, 2018 at 02:50:40PM +0800, Pingfan Liu wrote:
> commit 52cdbdd49853 ("driver core: correct device's shutdown order")
> places an assumption of supplier<-consumer order on the process of probe.
> But it turns out to break down the parent <- child order in some scene.
> E.g in pci, a bridge is enabled by pci core, and behind it, the devices
> have been probed. Then comes the bridge's module, which enables extra
> feature(such as hotplug) on this bridge. This will break the
> parent<-children order and cause failure when "kexec -e" in some scenario.
> The detailed description of the scenario:
> An IBM Power9 machine on which, two drivers portdrv_pci and shpchp(a mod)
> match the PCI_CLASS_BRIDGE_PCI, but neither of them success to probe due
> to some issue. For this case, the bridge is moved after its children in
> devices_kset. Then, when "kexec -e", a ata-disk behind the bridge can not
> write back buffer in flight due to the former shutdown of the bridge which
> clears the BusMaster bit.

If you revert commit cc27b735ad3a ("PCI/portdrv: Turn off PCIe services
during shutdown"), does the issue go away?