On Fri, Oct 13, 2017 at 09:35:40PM +0300, Mika Westerberg wrote: > Currently when plugging PCIe device using native PCIe hotplug Linux PCI > core tries to allocate bus space and resources so that the newly enumerated > topology barely fits there. Now, if the PCIe topology that was just plugged > in has more PCIe hotplug ports we will run out of bus space and resources > pretty quickly. There is a workaround for this by passing pci=hpbussize=N > in the kernel command line but it runs to the same situation after next > hotplug. > > A good example where this is a problem is Thunderbolt where each > Thunderbolt device includes PCIe switch and the topology can be extended up > to 6 chained devices. > > Future platforms will move from BIOS assisted (ACPI) hotplug from native > PCIe hotplug because then it is possible to power down PCIe hotplug ports > without confusing the SMI handler which is not necessary when native PCIe > hotplug is used. Also Apple Macs have been using native PCIe hotplug from > the beginning. Windows already knows how to handle these complex PCIe > topologies and we will reuse the same knowledge in Linux with this patch > series. > > The idea is to distribute available bus space and resources to hotplug PCIe > downstream ports so that the PCIe chain can be extended from those points. > The initial available space is configured by the BIOS to the root port in > question. > > This series first teaches the Linux PCI core to distribute available bus > space and resources if PCIe hotplug is used. Then following are fixes for > issues found while testing. > > With this series applied I can connect the maximum length Thunderbolt PCIe > chain (6 devices) to a Macbook Pro as can be seen from the 'lspci -t' > output below: > > -[0000:00]-+-00.0 > +-02.0 > +-14.0 > +-16.0 > +-19.0 > +-1c.0-[01]----00.0 > +-1c.4-[03-78]----00.0-[04-78]--+-00.0-[05]----00.0 > | +-01.0-[07-3f]----00.0-[08-3f]--+-01.0-[09]----00.0 > | | \-04.0-[0a-3f]----00.0-[0b-3f]--+-01.0-[0c]----00.0 > | | \-04.0-[0d-3f]----00.0-[0e-3f]--+-01.0-[0f]-- > | | \-04.0-[10-3f]----00.0-[11-3f]--+-01.0-[12]----00.0 > | | \-04.0-[13-3f]----00.0-[14-3f]--+-01.0-[15]----00.0 > | | \-04.0-[16-3f]----00.0-[17-3f]----00.0-[18-3f]----00.0 > | +-02.0-[06]----00.0 > | \-04.0-[40-78]-- > +-1d.0-[79-ee]----00.0-[7a-ee]--+-00.0-[7b]----00.0 > | +-01.0-[7d-b5]-- > | +-02.0-[7c]----00.0 > | \-04.0-[b6-ee]-- > +-1d.3-[02]----00.0 > +-1e.0 > +-1e.1 > +-1e.3 > +-1f.0 > +-1f.2 > +-1f.3 > \-1f.4 > > The previous version (v1) of the patch series can be found here: > > https://www.spinics.net/lists/linux-pci/msg64841.html > > Changes from v1: > > * Rebase on top of Andy's for_each_pci_bridge() patch > * Move pci_hp_add_bridge() to drivers/pci/probe.c > * Split open-coding of the two pass scan loop into a separate patch > * Drop [PATCH 2/7] PCI: Introduce pcie_upstream_port() > * Keep pci_scan_bridge_extend() and pci_scan_child_bus_extend() internal > to drivers/pci/probe.c > * Add another separate loop to count number of hotplug and normal bridges > * Reword comment about two scans > * Generalize patches 4 and 5 so that they could work also on conventional > PCI by dropping tests for PCIe. > > Mika Westerberg (8): > PCI: Move pci_hp_add_bridge() to drivers/pci/probe.c > PCI: Open-code the two pass loop when scanning bridges > PCI: Do not allocate more buses than available in parent > PCI: Distribute available buses to hotplug capable bridges > PCI: Distribute available resources to hotplug capable bridges > PCI: pciehp: Fix race condition handling surprise link down > PCI: pciehp: Do not clear Presence Detect Changed during initialization > PCI: pciehp: Check that the device is really present before touching it > > drivers/pci/Makefile | 3 - > drivers/pci/hotplug-pci.c | 29 ------ > drivers/pci/hotplug/pciehp_ctrl.c | 7 +- > drivers/pci/hotplug/pciehp_hpc.c | 13 ++- > drivers/pci/hotplug/pciehp_pci.c | 18 +++- > drivers/pci/probe.c | 188 +++++++++++++++++++++++++++++++++++--- > drivers/pci/setup-bus.c | 177 +++++++++++++++++++++++++++++++++++ > 7 files changed, 379 insertions(+), 56 deletions(-) > delete mode 100644 drivers/pci/hotplug-pci.c Looks very nice! I applied all but the last patch ("Check that the device is really present") on pci/hotplug for v4.15, thanks!
