ARM/ARM64: PCI: PCI_PROBE_ONLY clean-up

Current arm/arm64 code prevents enabling resources in the respective pcibios_enable_device() callbacks if the PCI_PROBE_ONLY flag is set, in that on those platforms the resources tree was not validated properly since PCI resources are not currently claimed on arm/arm64 PCI_PROBE_ONLY systems.

This is a temporary kludge, in that PCI_PROBE_ONLY flag is used to describe systems with fixed resources, that can nonetheless be enabled through the standard pci_enable_resources() call present in PCI core code, (ie via the generic pcibios_enable_device() call).

To remove the PCI_PROBE_ONLY flag in arm/arm64 pcibios_enable_device() callbacks, the PCI host controllers that can be used with PCI_PROBE_ONLY configurations must make sure that devices resources are validated and inserted in the kernel resource tree even on PCI_PROBE_ONLY systems so that the generic pcibios_enable_device() generic code, while enabling resources (pci_enable_resources()), does not find dangling resources pointers (ie missing parent pointers) that are omens of an incomplete resource tree, causing failures in resources enablement.

PCI core code provides interfaces to assign/reassign/reallocate PCI bus resources but it is currently lacking an interface to claim resources for a specific bus. Arches implement resources claiming through ad-hoc code built on top of pci_claim_resource() API, but that code cannot be leveraged on architectures like arm/arm64 that rely on the generic PCI infrastructure to carry out resources claiming/assignment.

Therefore, to clean up the arm/arm64 resources enablement on PCI_PROBE_ONLY systems this patchset implements four patches:

PATCH 1: Create PCI core code infrastructure to claim bus resources PATCH 2: Leverage the infrastructure in PATCH 1 to claim resources in
the PCI generic host controller on PCI_PROBE_ONLY systems

PATCH 3: Remove the PCI_PROBE_ONLY kludge from the arm64 PCI back-end to
complete the clean-up and leverage the PCI generic pcibios_enable_device() implementation

PATCH 4: Remove the PCI_PROBE_ONLY kludge from the arm PCI back-end to
complete the clean-up and leverage the PCI generic pcibios_enable_device() implementation

Tested on arm/arm64 systems with kvmtool and PCI host generic.

v2 -> v3

- Split patch 3 in two patches so that arm and arm64 are handled in different patches
- Improved commits logs, clarified resource parent assignment
- Rebased against v4.7-rc2

v2: https://patchwork.ozlabs.org/patch/590556/

v1 -> v2

- Rewrote patch 1 to recursively claim resources for the whole PCI bus hierarchy
- Updated commits logs/tags
- Rebased against v4.5-rc6

v1: https://patchwork.ozlabs.org/patch/545669/

Lorenzo Pieralisi (4):
PCI: add generic code to claim bus resources
PCI: host-generic: claim bus resources on PCI_PROBE_ONLY set-ups ARM64/PCI: remove arch specific pcibios_enable_device() ARM/PCI: remove arch specific pcibios_enable_device()

 arch/arm/kernel/bios32.c           | 12 -------
 arch/arm64/kernel/pci.c            | 13 --------
 drivers/pci/host/pci-host-common.c | 27 +++++++++++++--
 drivers/pci/setup-bus.c            | 68 ++++++++++++++++++++++++++++++++++++++
 include/linux/pci.h                |  1 +
 5 files changed, 94 insertions(+), 27 deletions(-)