Re: [PATCH v2 00/19] Add support for the LAN966x PCI device using a DT overlay

[Rob Herring <robh@kernel.org>]

On Mon, May 27, 2024 at 06:14:27PM +0200, Herve Codina wrote:
> Hi,
> 
> This series adds support for the LAN966x chip when used as a PCI
> device.
> 
> For reference, the LAN996x chip is a System-on-chip that integrates an
> Ethernet switch and a number of other traditional hardware blocks such
> as a GPIO controller, I2C controllers, SPI controllers, etc. The
> LAN996x can be used in two different modes:
> 
> - With Linux running on its Linux built-in ARM cores.
>   This mode is already supported by the upstream Linux kernel, with the
>   LAN996x described as a standard ARM Device Tree in
>   arch/arm/boot/dts/microchip/lan966x.dtsi. Thanks to this support,
>   all hardware blocks in the LAN996x already have drivers in the
>   upstream Linux kernel.
> 
> - As a PCI device, thanks to its built-in PCI endpoint controller.
>   In this case, the LAN996x ARM cores are not used, but all peripherals
>   of the LAN996x can be accessed by the PCI host using memory-mapped
>   I/O through the PCI BARs.
> 
> This series aims at supporting this second use-case. As all peripherals
> of the LAN996x already have drivers in the Linux kernel, our goal is to
> re-use them as-is to support this second use-case.
> 
> Therefore, this patch series introduces a PCI driver that binds on the
> LAN996x PCI VID/PID, and when probed, instantiates all devices that are
> accessible through the PCI BAR. As the list and characteristics of such
> devices are non-discoverable, this PCI driver loads a Device Tree
> overlay that allows to teach the kernel about which devices are
> available, and allows to probe the relevant drivers in kernel, re-using
> all existing drivers with no change.
> 
> This patch series for now adds a Device Tree overlay that describes an
> initial subset of the devices available over PCI in the LAN996x, and
> follow-up patch series will add support for more once this initial
> support has landed.
> 
> In order to add this PCI driver, a number of preparation changes are
> needed:
> 
>  - Patches 1 to 5 allow the reset driver used for the LAN996x to be
>    built as a module. Indeed, in the case where Linux runs on the ARM
>    cores, it is common to have the reset driver built-in. However, when
>    the LAN996x is used as a PCI device, it makes sense that all its
>    drivers can be loaded as modules.
> 
>  - Patches 6 and 7 improve the MDIO controller driver to properly
>    handle its reset signal.
> 
>  - Patches 8 to 12 introduce the internal interrupt controller used in
>    the LAN996x. It is one of the few peripherals in the LAN996x that
>    are only relevant when the LAN996x is used as a PCI device, which is
>    why this interrupt controller did not have a driver so far.
> 
>  - Patches 13 to 16 make some small additions to the OF core and
>    PCI/OF core to consider the PCI device as an interrupt controller.
>    This topic was previously mentioned in [1] to avoid the need of
>    phandle interrupt parents which are not available at some points.
> 
>  - Patches 17 and 18 introduce the LAN996x PCI driver itself, together
>    with its DT bindings.
> 
> We believe all items from the above list can be merged separately, with
> no build dependencies. We expect:
> 
>  - Patches 1 to 5 to be taken by reset maintainers
> 
>  - Patches 6 and 7 to be taken by network driver maintainers
> 
>  - Patches 8 to 12 to be taken by irqchip maintainers
> 
>  - Patch 13 to 17 to be taken by DT/PCI maintainers

I've applied patches 13-17.

Rob