Re: [PATCH v7 0/5] Add support for the PCI host bridge device-tree node creation.

[Rob Herring]

On Tue, Feb 04, 2025 at 08:34:55AM +0100, Herve Codina wrote:
> Hi,
> 
> This series adds support for creating a device-tree node for the PCI
> host bridge on non device-tree based system.
> 
> Creating device-tree nodes for PCI devices and PCI-PCI bridges already
> exists upstream. It was added in commit 407d1a51921e ("PCI: Create
> device tree node for bridge"). Created device-tree nodes need a parent
> node to be attached to. For the first level devices, on device-tree
> based system, this parent node (i.e. the PCI host bridge) is described
> in the base device-tree. The PCI bus related to this bridge (PCI root
> bus) inherit of the PCI host bridge device-tree node.
> 
> The LAN966x PCI device driver, available since commit 185686beb464
> ("misc: Add support for LAN966x PCI device"), relies on this feature.
> 
> On system where the base hardware is not described by a device-tree, the
> PCI host bridge to which first level created PCI devices need to be
> attach to does not exist. This is the case for instance on ACPI
> described systems such as x86.
> 
> This series goal is to handle this case.
> 
> In order to have the PCI host bridge device-tree node available even
> on x86, this top level node is created (if not already present) based on
> information computed by the PCI core. It follows the same mechanism as
> the one used for PCI devices device-tree node creation.
> 
> As for device-tree based system, the PCI root bus handled by the PCI
> host bridge inherit of this created node.
> 
> In order to have this feature available, a number of changes are needed:
>   - Patch 1 and 2: Introduce and use device_{add,remove}_of_node().
>     This function will also be used in the root PCI bus node creation.
> 
>   - Patch 3 and 4: Improve existing functions to reuse them in the root
>     PCI bus node creation.
> 
>   - Patch 5: The PCI host bridge device-tree node creation itself.
> 
> With those modifications, the LAN966x PCI device is working on x86 systems
> and all device-tree kunit tests (including the of_unittest_pci_node test)
> pass successfully with the following command:
>   qemu-system-x86_64 -machine q35 -nographic \
>     -kernel arch/x86_64/boot/bzImage --append console=ttyS0 \
>     -device pcie-root-port,port=0x10,chassis=9,id=pci.9,bus=pcie.0,multifunction=on,addr=0x3 \
>     -device pcie-root-port,port=0x11,chassis=10,id=pci.10,bus=pcie.0,addr=0x3.0x1 \
>     -device x3130-upstream,id=pci.11,bus=pci.9,addr=0x0 \
>     -device xio3130-downstream,port=0x0,chassis=11,id=pci.12,bus=pci.11,multifunction=on,addr=0x0 \
>     -device i82801b11-bridge,id=pci.13,bus=pcie.0,addr=0x4 \
>     -device pci-bridge,chassis_nr=14,id=pci.14,bus=pci.13,addr=0x0 \
>     -device pci-testdev,bus=pci.12,addr=0x0
> 
> Compare to previous iteration, this v7 series is the v6 series rebased
> on top of v6.14-rc1 without other modifications.
> 
> Best regards,
> Hervé Codina
> 
> Changes v6 -> v7
>   v6: https://lore.kernel.org/lkml/20250110082143.917590-1-herve.codina@xxxxxxxxxxx/
> 
>   Rebase on top of v6.14-rc1
> 
> Changes v5 -> v6
>   v5: https://lore.kernel.org/lkml/20241209130339.81354-1-herve.codina@xxxxxxxxxxx/
> 
>   - Patch 1
>     Add a return error code in device_add_of_node()
> 
>   - Patches 2 and 5
>     Handle the device_add_of_node() error code
> 
>   - Patches 3 and 4
>     No changes
> 
> Changes v4 -> v5
>   v4: https://lore.kernel.org/lkml/20241202131522.142268-1-herve.codina@xxxxxxxxxxx/
> 
>   - Patch 1
>     Use dev_warn() instead of WARN()
> 
>   - Patches 2 to 4
>     No changes
> 
>   - Patch 5 (v4 patch 6)
>     Use dev_err()
>     Fix a typo in commit log
> 
>   Patch removed in v5
>     - Patch 5 in v4
>       Already applied
> 
> Changes v3 -> v4
>   v3: https://lore.kernel.org/lkml/20241114165446.611458-1-herve.codina@xxxxxxxxxxx/
> 
>   Rebase on top of v6.13-rc1
> 
>   - Patches 1 to 6
>     No changes
> 
> Changes v2 -> v3
>   v2: https://lore.kernel.org/lkml/20241108143600.756224-1-herve.codina@xxxxxxxxxxx/
> 
>   - Patch 5
>     Fix commit log.
>     Use 2 for #size-cells.
> 
>   - Patches 1 to 4 and 6
>     No changes
> 
> Changes v1 -> v2
>   v1: https://lore.kernel.org/lkml/20241104172001.165640-1-herve.codina@xxxxxxxxxxx/
> 
>   - Patch 1
>     Remove Cc: stable
> 
>   - Patch 2
>     Remove Fixup tag and Cc: stable
> 
>   - Patches 3 and 4
>     No changes
> 
>   - Patch 5
>     Add #address-cells/#size-cells in the empty root DT node instead of
>     updating default values for x86.
>     Update commit log and commit title.
> 
>   - Patch 6
>     Create device-tree node for the PCI host bridge and reuse it for
>     the PCI root bus. Rename functions accordingly.
>     Use "pci" instead of "pci-root" for the PCI host bridge node name.
>     Use "res->start - windows->offset" for the PCI bus addresses.
>     Update commit log and commit title.
> 
> Herve Codina (5):
>   driver core: Introduce device_{add,remove}_of_node()
>   PCI: of: Use device_{add,remove}_of_node() to attach of_node to
>     existing device
>   PCI: of_property: Add support for NULL pdev in of_pci_set_address()
>   PCI: of_property: Constify parameter in of_pci_get_addr_flags()
>   PCI: of: Create device-tree PCI host bridge node
> 
>  drivers/base/core.c       |  61 ++++++++++++++++++++
>  drivers/pci/of.c          | 115 +++++++++++++++++++++++++++++++++++++-
>  drivers/pci/of_property.c | 114 +++++++++++++++++++++++++++++++++++--
>  drivers/pci/pci.h         |   6 ++
>  drivers/pci/probe.c       |   2 +
>  drivers/pci/remove.c      |   2 +
>  include/linux/device.h    |   2 +
>  7 files changed, 295 insertions(+), 7 deletions(-)

For the series,

Reviewed-by: Rob Herring (Arm) <robh@xxxxxxxxxx>