Re: [PATCH v9 -next 07/12] misc: rp1: RaspberryPi RP1 misc driver

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Tue, Apr 22, 2025 at 08:53:16PM +0200, Andrea della Porta wrote:
> The RaspberryPi RP1 is a PCI multi function device containing
> peripherals ranging from Ethernet to USB controller, I2C, SPI
> and others.
> 
> Implement a bare minimum driver to operate the RP1, leveraging
> actual OF based driver implementations for the on-board peripherals
> by loading a devicetree overlay during driver probe if the RP1
> node is not already present in the DT.
> 
> The peripherals are accessed by mapping MMIO registers starting
> from PCI BAR1 region.
> 
> With the overlay approach we can achieve more generic and agnostic
> approach to managing this chipset, being that it is a PCI endpoint
> and could possibly be reused in other hw implementations. The
> presented approach is also used by Bootlin's Microchip LAN966x
> patchset (see link) as well, for a similar chipset.
> In this case, the inclusion tree for the DT overlay is as follow
> (the arrow points to the includer):
> 
>  rp1-pci.dtso <---- rp1-common.dtsi
> 
> On the other hand, to ensure compatibility with downstream, this
> driver can also work with a DT already comprising the RP1 node, so
> the dynamically loaded overlay will not be used if the DT is already
> fully defined.
> 
> The reason why this driver is contained in drivers/misc has
> been paved by Bootlin's LAN966X driver, which first used the
> overlay approach to implement non discoverable peripherals behind a
> PCI bus. For RP1, the same arguments apply: it's not used as an SoC
> since the driver code is not running on-chip and is not like an MFD
> since it does not really need all the MFD infrastructure (shared regs,
> etc.). So, for this particular use, misc has been proposed and deemed
> as a good choice. For further details about that please check the links.
> 
> This driver is heavily based on downstream code from RaspberryPi
> Foundation, and the original author is Phil Elwell.
> 
> Link: https://datasheets.raspberrypi.com/rp1/rp1-peripherals.pdf
> Link: https://lore.kernel.org/all/20240612140208.GC1504919@google.com/
> Link: https://lore.kernel.org/all/83f7fa09-d0e6-4f36-a27d-cee08979be2a@app.fastmail.com/
> Link: https://lore.kernel.org/all/2024081356-mutable-everyday-6f9d@gregkh/
> Link: https://lore.kernel.org/all/20240808154658.247873-1-herve.codina@bootlin.com/
> 
> Signed-off-by: Andrea della Porta <andrea.porta@suse.com>
> Acked-by: Bjorn Helgaas <bhelgaas@google.com>   # quirks.c, pci_ids.h
> ---
>  MAINTAINERS                   |   1 +
>  drivers/misc/Kconfig          |   1 +
>  drivers/misc/Makefile         |   1 +
>  drivers/misc/rp1/Kconfig      |  20 ++
>  drivers/misc/rp1/Makefile     |   3 +
>  drivers/misc/rp1/rp1-pci.dtso |  25 +++
>  drivers/misc/rp1/rp1_pci.c    | 333 ++++++++++++++++++++++++++++++++++
>  drivers/pci/quirks.c          |   1 +
>  include/linux/pci_ids.h       |   3 +
>  9 files changed, 388 insertions(+)
>  create mode 100644 drivers/misc/rp1/Kconfig
>  create mode 100644 drivers/misc/rp1/Makefile
>  create mode 100644 drivers/misc/rp1/rp1-pci.dtso
>  create mode 100644 drivers/misc/rp1/rp1_pci.c


Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>