Re: [PATCH v8 08/13] misc: rp1: RaspberryPi RP1 misc driver

Bjorn Helgaas
2025-04-16T19:34:01Z

On Wed, Mar 19, 2025 at 10:52:29PM +0100, 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

> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index b84ff7bade82..4dfda527c76b 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -6283,6 +6283,7 @@ DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_XILINX, 0x5020, of_pci_make_dev_node);
> DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_XILINX, 0x5021, of_pci_make_dev_node);
> DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_REDHAT, 0x0005, of_pci_make_dev_node);
> DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_EFAR, 0x9660, of_pci_make_dev_node);
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_RPI, PCI_DEVICE_ID_RPI_RP1_C0, of_pci_make_dev_node);
>
> /*
> * Devices known to require a longer delay before first config space access
> diff --git a/include/linux/pci_ids.h b/include/linux/pci_ids.h
> index de5deb1a0118..b7a2c0fd589e 100644
> --- a/include/linux/pci_ids.h
> +++ b/include/linux/pci_ids.h
> @@ -2620,6 +2620,9 @@
> #define PCI_VENDOR_ID_TEKRAM 0x1de1
> #define PCI_DEVICE_ID_TEKRAM_DC290 0xdc29
>
> +#define PCI_VENDOR_ID_RPI 0x1de4
> +#define PCI_DEVICE_ID_RPI_RP1_C0 0x0001
> +
> #define PCI_VENDOR_ID_ALIBABA 0x1ded
>
> #define PCI_VENDOR_ID_CXL 0x1e98
> --
> 2.35.3
>