From: Florian Fainelli <f.fainelli@xxxxxxxxx> On Thu, 29 May 2025 15:50:44 +0200, Andrea della Porta <andrea.porta@xxxxxxxx> 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@xxxxxxxxxx/ > Link: https://lore.kernel.org/all/83f7fa09-d0e6-4f36-a27d-cee08979be2a@xxxxxxxxxxxxxxxx/ > Link: https://lore.kernel.org/all/2024081356-mutable-everyday-6f9d@gregkh/ > Link: https://lore.kernel.org/all/20240808154658.247873-1-herve.codina@xxxxxxxxxxx/ > > Signed-off-by: Andrea della Porta <andrea.porta@xxxxxxxx> > Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> # quirks.c, pci_ids.h > Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > --- Applied to https://github.com/Broadcom/stblinux/commits/drivers/next, thanks! -- Florian
