PCI: Fixes and cleanups for native PCIe, SHPC and ACPI hotplug

When Thunderbolt host router is configured to be in native enumeration mode it is only present in the system if there is something connected to the ports. This pretty much follows how the BIOS assisted mode works.

In native enumeration mode the Thunderbolt host controller (NHI) and USB host controller (xHCI) are not hot-added using native PCIe hotplug but instead they will be hotplugged via BIOS triggered ACPI Notify() to the root port. This is done to preserve resources since NHI and xHCI only need 1 MB of MMIO space and no additional buses. Currently Linux does not support this very well and ends up failing the hotplug in one way or another. More detailed explanation is in changelog of patch [4/7].

This series fixes this issue and in addition includes fixes for few other issues found during testing on a system that has Thunderbolt controller in native PCIe enumeration mode. However, the fixes here are not in any way Thunderbolt specific and should be applicable to other systems as well.

The previous versions of the patch series can be found here:

v7: https://www.spinics.net/lists/linux-pci/msg72558.html
v6: https://www.spinics.net/lists/linux-pci/msg72267.html
v5: https://www.spinics.net/lists/linux-pci/msg71339.html
v4: https://www.spinics.net/lists/linux-pci/msg71006.html
v3: https://www.spinics.net/lists/linux-acpi/msg80876.html
v2: https://www.spinics.net/lists/linux-pci/msg69186.html
v1: https://www.spinics.net/lists/linux-acpi/msg80607.html

Changes from v7:

- Rebased on top of pci.git pci/hotplug
- Make acpi_get_hp_hw_control_from_firmware() call shpchp_is_native()
- Drop !bridge check from shpchp_is_native() and update callers to handle possibly NULL pdev
- Split out hotplug_is_native() into a separate patch

Changes from v6:

- Use IS_ENABLED(CONFIG_HOTPLUG_PCI_PCIE) and IS_ENABLED(CONFIG_HOTPLUG_PCI_SHPC) directly instaed of wrapping them in macro
- Check for !bridge in the same condition than we check whether certain native hotplug is enabled
- Add Rafael's Reviewed-by

Changes from v5:

- Dropped patch "PCI: Take bridge window alignment into account when distributing resources"
- Rework pciehp_is_native() to be more stricter
- Make standard PCI hotplug driver (SHPC) builtin
- Rework the way we request OS control of native PCIe hotplug (pciehp) and standard PCI hotplug (SHPC)
- Make acpiphp to avoid bridges where hotplug_is_native() returns true (this is combined from pciehp and SHPC)
- Updated changelog of patch [7/12]
- Use hotplug_bridges + normal_bridges == 1 in patch [9/12] and also remove one indent level from the loop.

Because patch [7/12] looks quite different now I dropped Reviewed-by and stable tag (it now depends on reworked pciehp/SHCP support that most probably is not suitable for stable trees).

I also was not able to test that SHPC really works because I don't have hardware that supports it.

Changes from v4:

- Updated message in patch [8/9] following Rafael's suggestion
- Added Rafael's tag to patches 6, 7, 9.

Changes from v3:

- Added Andy's tag to patches [1-5]
- Improved changelog and subject line of patch [1/9] to match better what it is trying to solve
- Improved comment in patch [1/9]
- Improved changelog of patches [2/9] and [4/9] accordingly to match better why they are needed
- Added cleanup patches [6-9/9]

Changes from v2:

- Added Rafael's tag to patch [1/5]
- Updated changelog of patch [1/5] to include more details about how the problem can be observed from dmesg and lspci output

Changes from v1:

- Drop 'cmax - max ?: 1' and use similar construct than we use in second pass loop in patch [1/5]
- Drop unnecessary parentheses in patch [1/5]
- Added Rafael's tag to patches [2-5/5]

Mika Westerberg (7):
PCI: Take all bridges into account when calculating bus numbers for extension
PCI: Introduce shpchp_is_native()
PCI: Introduce hotplug_is_native()
ACPI / hotplug / PCI: Do not scan all bridges when native PCIe hotplug is used ACPI / hotplug / PCI: Mark stale PCI devices disconnected
PCI: Move resource distribution for a single bridge outside of the loop
PCI: Document return value of pci_scan_bridge() and pci_scan_bridge_extend()

 drivers/pci/hotplug/acpi_pcihp.c   |  4 +-
 drivers/pci/hotplug/acpiphp_glue.c | 80 ++++++++++++++++++++++-------
 drivers/pci/hotplug/shpchp_core.c  |  2 -
 drivers/pci/pci-acpi.c             | 21 ++++++++
 drivers/pci/probe.c                | 19 +++++--
 drivers/pci/setup-bus.c            | 82 +++++++++++++++---------------
 include/linux/pci_hotplug.h        |  7 +++
 7 files changed, 150 insertions(+), 65 deletions(-)

2.17.0