Le Sun, 26 Feb 2023 16:38:58 -0600, Frank Rowand <frowand.list@xxxxxxxxx> a écrit : > Hi Clément, Hi Lizhi, > > On 1/19/23 21:02, 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 > > > > Digging back through some history: > > > Please see: https://lore.kernel.org/lkml/20220427094502.456111-1-clement.leger@xxxxxxxxxxx/ > > (I am selectively pulling two fragments, see the above link for the > full email.) > > Includes the following: > > A driver using this support was added and can be seen at [3]. This > driver embeds a builtin overlay and applies it to the live tree using > of_overlay_fdt_apply_to_node(). An interrupt driver is also included and > > and > > This series was tested on a x86 kernel using CONFIG_OF under a virtual > machine using PCI passthrough. > > Link: [1] https://lore.kernel.org/lkml/YhQHqDJvahgriDZK@xxxxxxx/t/ > Link: [2] https://lore.kernel.org/lkml/20220408174841.34458529@xxxxxxxxx/T/ > Link: [3] https://github.com/clementleger/linux/tree/lan966x/of_support > > Following link 3 to see how the driver implemented the concept, I arrived > at a git tree, with the commit be42efa "mfd: lan966x: add pci driver", > and have been looking at the code there. > > Clément, is this still the best example of a driver implementation that > would use the framework proposed in the "[PATCH V7 0/3] Generate device > tree node for pci devices" patch series? And this is the driver for the > device listed as item 2 above "2) Microchip LAN9662 Ethernet Controller"? Hi Frank, The driver has slightly evolved to be based on Lizhi Patches and the interrupt driver was reworked to be a standard platform driver. I'll clean that up and push a new branch based on this work. This driver is indeed the driver for the LAN9662 Ethernet Controller which allows using the 2 SFPs ports and 2 RJ45 ports successfully (which involves multiple subsystem and drivers). While doing this work, I found multiple of_noderefcount issues which I fixed and that are currently being reviewed. I won't be surprised if there are other lying around in various part of the kernel. Just saying so you know there is actually effort to make that more robust. Clément > > -Frank > > > > > 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@xxxxxxxxx/ > > https://lore.kernel.org/lkml/20220216050056.311496-1-lizhi.hou@xxxxxxxxxx/ > > > > 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. > > < snip > > -- Clément Léger, Embedded Linux and Kernel engineer at Bootlin https://bootlin.com
