Re: [PATCH v3 0/4] ARM/ARM64: PCI: PCI_PROBE_ONLY clean-up

[Bjorn Helgaas <helgaas@kernel.org>]

On Wed, Jun 08, 2016 at 12:04:46PM +0100, Lorenzo Pieralisi wrote:
> 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(-)

I applied these to pci/resource for v4.8, thanks, Lorenzo!

It's awesome to get rid of that PCI_PROBE_ONLY hack.

We might still tweak this a little based on my question about
pci_common_init_dev(), so don't build things on top of this yet (good
advice in general for my branches: I often rebase and remerge them, so
it's best to base things on my "master" branch unless you actually
depend on something that's not in there.)