linux-kernel - Re: [RESEND PATCH RFC V4 0/3] Generate device tree node for pci devices

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Message-ID: <9d21aa8f-6581-a4bf-644a-6e273373afc4@amd.com>
Date:   Wed, 30 Nov 2022 21:50:56 -0800
From:   Sonal Santan <sonal.santan@....com>
To:     Lizhi Hou <lizhi.hou@....com>, linux-pci@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        robh@...nel.org, frowand.list@...il.com, helgaas@...nel.org
Cc:     clement.leger@...tlin.com, max.zhen@....com, larry.liu@....com,
        brian.xu@....com, stefano.stabellini@...inx.com, trix@...hat.com
Subject: Re: [RESEND PATCH RFC V4 0/3] Generate device tree node for pci
 devices

On 11/21/22 08:43, Lizhi Hou wrote:
> This patch series introduces OF overlay support for PCI devices which
> primarily addresses two use cases. First, it provides a data driven method
> to describe hardware peripherals that are present in a PCI endpoint and
> hence can be accessed by the PCI host. Second, it allows reuse of a OF
> compatible driver -- often used in SoC platforms -- in a PCI host based
> system.
> 
> There are 2 series devices rely on this patch:
> 
>   1) Xilinx Alveo Accelerator cards (FPGA based device)
>   2) Microchip LAN9662 Ethernet Controller
> 
>      Please see: https://lore.kernel.org/lkml/20220427094502.456111-1-clement.leger@bootlin.com/
> 
> Normally, the PCI core discovers PCI devices and their BARs using the
> PCI enumeration process. However, the process does not provide a way to
> discover the hardware peripherals that are present in a PCI device, and
> which can be accessed through the PCI BARs. Also, the enumeration process
> does not provide a way to associate MSI-X vectors of a PCI device with the
> hardware peripherals that are present in the device. PCI device drivers
> often use header files to describe the hardware peripherals and their
> resources as there is no standard data driven way to do so. This patch
> series proposes to use flattened device tree blob to describe the
> peripherals in a data driven way. Based on previous discussion, using
> device tree overlay is the best way to unflatten the blob and populate
> platform devices. To use device tree overlay, there are three obvious
> problems that need to be resolved.
> 
> First, we need to create a base tree for non-DT system such as x86_64. A
> patch series has been submitted for this:
> https://lore.kernel.org/lkml/20220624034327.2542112-1-frowand.list@gmail.com/
> https://lore.kernel.org/lkml/20220216050056.311496-1-lizhi.hou@xilinx.com/
> 
> Second, a device tree node corresponding to the PCI endpoint is required
> for overlaying the flattened device tree blob for that PCI endpoint.
> Because PCI is a self-discoverable bus, a device tree node is usually not
> created for PCI devices. This series adds support to generate a device
> tree node for a PCI device which advertises itself using PCI quirks
> infrastructure.
> 
> Third, we need to generate device tree nodes for PCI bridges since a child
> PCI endpoint may choose to have a device tree node created.
> 
> This patch series is made up of three patches.
> 
> The first patch is adding OF interface to create or destroy OF node
> dynamically.
> 
> The second patch introduces a kernel option, CONFIG_DYNAMIC_PCI_OF_NODEX.
> When the option is turned on, the kernel will generate device tree nodes
> for all PCI bridges unconditionally. The patch also shows how to use the
> PCI quirks infrastructure, DECLARE_PCI_FIXUP_FINAL to generate a device
> tree node for a device. Specifically, the patch generates a device tree
> node for Xilinx Alveo U50 PCIe accelerator device. The generated device
> tree nodes do not have any property.
> 
> The third patch adds basic properties ('reg', 'compatible' and
> 'device_type') to the dynamically generated device tree nodes. More
> properties can be added in the future.
> 
> Here is the example of device tree nodes generated within the ARM64 QEMU.
> # lspci -t    
> -[0000:00]-+-00.0
>            +-01.0-[01]--
>            +-01.1-[02]----00.0
>            +-01.2-[03]----00.0
>            +-01.3-[04]----00.0
>            +-01.4-[05]----00.0
>            +-01.5-[06]--
>            +-01.6-[07]--
>            +-01.7-[08]--
>            +-02.0-[09-0b]----00.0-[0a-0b]----00.0-[0b]--+-00.0
>            |                                            \-00.1
>            +-02.1-[0c]--
>            \-03.0-[0d-0e]----00.0-[0e]----01.0
> 
> # tree /sys/firmware/devicetree/base/pcie\@10000000
> /sys/firmware/devicetree/base/pcie@...00000
> |-- #address-cells
> |-- #interrupt-cells
> |-- #size-cells
> |-- bus-range
> |-- compatible
> |-- device_type
> |-- dma-coherent
> |-- interrupt-map
> |-- interrupt-map-mask
> |-- linux,pci-domain
> |-- msi-parent
> |-- name
> |-- pci@1,0
> |   |-- #address_cells
> |   |-- #size_cells
> |   |-- compatible
> |   |-- device_type
> |   |-- ranges
> |   `-- reg
> |-- pci@1,1
> |   |-- #address_cells
> |   |-- #size_cells
> |   |-- compatible
> |   |-- device_type
> |   |-- ranges
> |   `-- reg
> |-- pci@1,2
> |   |-- #address_cells
> |   |-- #size_cells
> |   |-- compatible
> |   |-- device_type
> |   |-- ranges
> |   `-- reg
> |-- pci@1,3
> |   |-- #address_cells
> |   |-- #size_cells
> |   |-- compatible
> |   |-- device_type
> |   |-- ranges
> |   `-- reg
> |-- pci@1,4
> |   |-- #address_cells
> |   |-- #size_cells
> |   |-- compatible
> |   |-- device_type
> |   |-- ranges
> |   `-- reg
> |-- pci@1,5
> |   |-- #address_cells
> |   |-- #size_cells
> |   |-- compatible
> |   |-- device_type
> |   |-- ranges
> |   `-- reg
> |-- pci@1,6
> |   |-- #address_cells
> |   |-- #size_cells
> |   |-- compatible
> |   |-- device_type
> |   |-- ranges
> |   `-- reg
> |-- pci@1,7
> |   |-- #address_cells
> |   |-- #size_cells
> |   |-- compatible
> |   |-- device_type
> |   |-- ranges
> |   `-- reg
> |-- pci@2,0
> |   |-- #address_cells
> |   |-- #size_cells
> |   |-- compatible
> |   |-- device_type
> |   |-- pci@0,0
> |   |   |-- #address_cells
> |   |   |-- #size_cells
> |   |   |-- compatible
> |   |   |-- device_type
> |   |   |-- pci@0,0
> |   |   |   |-- #address_cells
> |   |   |   |-- #size_cells
> |   |   |   |-- compatible
> |   |   |   |-- dev@0,0
> |   |   |   |   |-- compatible
> |   |   |   |   `-- reg
> |   |   |   |-- dev@0,1
> |   |   |   |   |-- compatible
> |   |   |   |   `-- reg
> |   |   |   |-- device_type
> |   |   |   |-- ranges
> |   |   |   `-- reg
> |   |   |-- ranges
> |   |   `-- reg
> |   |-- ranges
> |   `-- reg
> |-- pci@2,1
> |   |-- #address_cells
> |   |-- #size_cells
> |   |-- compatible
> |   |-- device_type
> |   |-- ranges
> |   `-- reg
> |-- pci@3,0
> |   |-- #address_cells
> |   |-- #size_cells
> |   |-- compatible
> |   |-- device_type
> |   |-- pci@0,0
> |   |   |-- #address_cells
> |   |   |-- #size_cells
> |   |   |-- compatible
> |   |   |-- device_type
> |   |   |-- ranges
> |   |   `-- reg
> |   |-- ranges
> |   `-- reg
> |-- ranges
> `-- reg
> 
> Changes since RFC v3:
> - Split the Xilinx Alveo U50 PCI quirk to a separate patch
> - Minor changes in commit description and code comment
> 
> Changes since RFC v2:
> - Merged patch 3 with patch 2
> - Added OF interfaces of_changeset_add_prop_* and use them to create
>   properties.
> - Added '#address-cells', '#size-cells' and 'ranges' properties.
> 
> Changes since RFC v1:
> - Added one patch to create basic properties.
> - To move DT related code out of PCI subsystem, replaced of_node_alloc()
>   with of_create_node()/of_destroy_node()
> 
> Lizhi Hou (3):
>   of: dynamic: Add interfaces for creating device node dynamically
>   PCI: Create device tree node for selected devices
>   PCI: Add PCI quirks to generate device tree node for Xilinx Alveo U50
> 
>  drivers/of/dynamic.c        | 187 ++++++++++++++++++++++++++
>  drivers/pci/Kconfig         |  12 ++
>  drivers/pci/Makefile        |   1 +
>  drivers/pci/bus.c           |   2 +
>  drivers/pci/msi/irqdomain.c |   6 +-
>  drivers/pci/of.c            |  71 ++++++++++
>  drivers/pci/of_property.c   | 256 ++++++++++++++++++++++++++++++++++++
>  drivers/pci/pci-driver.c    |   3 +-
>  drivers/pci/pci.h           |  19 +++
>  drivers/pci/quirks.c        |  11 ++
>  drivers/pci/remove.c        |   1 +
>  include/linux/of.h          |  24 ++++
>  12 files changed, 590 insertions(+), 3 deletions(-)
>  create mode 100644 drivers/pci/of_property.c
> 
Hello,

This RFC patch set has been patiently waiting for attention. If there
are no additional comments can it move forward?

-Sonal