Add support for RaspberryPi RP1 PCI device using a DT overlay

*** RESENDING PATCHSET SINCE LAST ONE HAS CLOBBERED SEQUENCE NUMBER ***

RP1 is an MFD chipset that acts as a south-bridge PCIe endpoint sporting a pletora of subdevices (i.e. Ethernet, USB host controller, I2C, PWM, etc.) whose registers are all reachable starting from an offset from the BAR address. The main point here is that while the RP1 as an endpoint itself is discoverable via usual PCI enumeraiton, the devices it contains are not discoverable and must be declared e.g. via the devicetree.

This patchset is an attempt to provide a minimum infrastructure to allow the RP1 chipset to be discovered and perpherals it contains to be added from a devictree overlay loaded during RP1 PCI endpoint enumeration. To ensure compatibility with downstream, a devicetree already comprising the RP1 node is also provided, so it's not strictly necessary to use the dynamically loaded overlay if the devicetree is already fully defined at the origin.
To achieve this modularity, the RP1 node DT definitions are arranged by file inclusion as per following schema (the arrow points to the includer, see also [9]):

rp1-pci.dtso rp1.dtso
^ ^
| |
rp1-common.dtsi ----> rp1-nexus.dtsi ----> bcm2712-rpi-5-b.dts

                                               ^
                                               |
                                           bcm2712-rpi-5-b-ovl-rp1.dts

Followup patches should add support for the several peripherals contained in RP1.

This work is based upon dowstream drivers code and the proposal from RH et al. (see [1] and [2]). A similar approach is also pursued in [3].

The patches are ordered as follows:

-PATCHES 1 to 3: add binding schemas for clock, gpio and RP1 peripherals.
They are needed to support the other peripherals, e.g. the ethernet mac depends on a clock generated by RP1 and the phy is reset through the on-board gpio controller.

-PATCH 4 and 5: add clock and gpio device drivers.

-PATCH 6: the devicetree node describing the RP1 chipset.

-PATCH 7: this is the main patch to support RP1 chipset. It can work
either with a fully defined devicetree (i.e. one that already included the rp1 node since boot time) or with a runtime loaded dtb overlay which is linked as binary blob in the driver obj. This duality is useful to comply with both downstream and upstream needs (see [9]). The real dtso is in devicetree folder while the dtso in driver folder is just a placeholder to include the real dtso.
In this way it is possible to check the dtso against dt-bindings. The reason why drivers/misc has been selected as containing folder for this driver can be seen in [6], [7] and [8].

-PATCH 8: add the external clock node (used by RP1) to the main dts.

-PATCH 9: the fully fledged devictree containing also the rp1 node.
This devicetree is functionally similar to the one downstream is using.

-PATCH 10 (OPTIONAL): this patch introduces a new scenario about how
the rp1 node is specified and loaded in DT. On top of the base DT (without rp1 node), the fw loads this overlay and the end result is the same devicetree as in patch 9, which is then passed to the next stage (either the kernel or u-boot/bootloader).
While this patch is not strictly necessary and can therefore be dropped (see [10]), it's not introducing much extra work and maybe can come in handy while debugging.

-PATCH 11: add the relevant kernel CONFIG_ options to defconfig.

-PATCH 12: enable CONFIG_OF_OVERLAY in order for 'make defconfig'
to produce a configuration valid for the RP1 driver. Without this patch, the user has to explicitly enable it since the misc driver depends on OF_OVERLAY.

-PATCH 13: collect all changes for MAINTAINERS file.

This patchset is also a first attempt to be more agnostic wrt hardware description standards such as OF devicetree and ACPI, where 'agnostic' means "using DT in coexistence with ACPI", as been already promoted by e.g. AL (see [4]). Although there's currently no evidence it will also run out of the box on purely ACPI system, it is a first step towards that direction.

Many thanks,
Andrea della Porta

Links:
- [1]: https://lpc.events/event/17/contributions/1421/attachments/1337/2680/LPC2023%20Non-discoverable%20devices%20in%20PCI.pdf
- [2]: https://lore.kernel.org/lkml/[email protected]/t/
- [3]: https://lore.kernel.org/all/[email protected]/#t
- [4]: https://lore.kernel.org/all/[email protected]/
- [5]: https://lore.kernel.org/all/[email protected]/
- [6]: https://lore.kernel.org/all/[email protected]/
- [7]: https://lore.kernel.org/all/[email protected]/
- [8]: https://lore.kernel.org/all/2024081356-mutable-everyday-6f9d@gregkh/
- [9]: https://lore.kernel.org/all/Z87wTfChRC5Ruwc0@apocalypse/
- [10]: https://lore.kernel.org/all/CAMEGJJ0f4YUgdWBhxvQ_dquZHztve9KO7pvQjoDWJ3=zd3cgcg@mail.gmail.com/#t

CHANGES IN V10

PATCH RELATED -------------------------------------------------

- Patch 10,11,12: Added: Reviewed-by: Reviewed-by: Florian Fainelli <[email protected]>

- Patches reworked to apply cleanly on broadcom/stblinux branches:
patch 1,2,3,6,8,9,10 -> devicetree/next
patch 11,12 -> defconfig/next
patch 4,5,7 -> drivers/next
patch 13 -> maintainers/next

- Patch 13: new patch gathering all changes for MAINTAINERS

RP1 CLOCK DRIVER ------------------------------------

- Dropped some WARN_ONCE() lines that are basically useless

- rp1_clock_set_parent() now returns EINVAL in case the parent check is failing. As a result, rp1_clock_set_rate_and_parent() has also been adapted to return rp1_clock_set_parent() retcode.

- Return an ERR_PTR from rp1_register_clock() instead of just NULL

- Dropped some unaesthetic blank lines

- Disabled the builtin locking in regmap since we're already dealing with concurrency in the code

- rp1_clk_probe(): dropped dev_err_probe() as redundant due to commit 12a0fd23e870 ("clk: Print an error when clk registration fails")

RaspberryPi RP1 is a multi function PCI endpoint device that exposes several subperipherals via PCI BAR.

Add a dtb overlay that will be compiled into a binary blob and linked in the RP1 driver.

This overlay offers just minimal support to represent the RP1 device itself, the sub-peripherals will be added by future patches.

---
 arch/arm64/boot/dts/broadcom/rp1-common.dtsi | 42 ++++++++++++++++++++
 arch/arm64/boot/dts/broadcom/rp1-nexus.dtsi  | 14 +++++++
 2 files changed, 56 insertions(+)
 create mode 100644 arch/arm64/boot/dts/broadcom/rp1-common.dtsi
 create mode 100644 arch/arm64/boot/dts/broadcom/rp1-nexus.dtsi

new file mode 100644
index 000000000000..5002a375eb0b
@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: (GPL-2.0 OR MIT)
+
+#include <dt-bindings/gpio/gpio.h>
+#include <dt-bindings/interrupt-controller/irq.h>
+#include <dt-bindings/clock/raspberrypi,rp1-clocks.h>
+
+pci_ep_bus: pci-ep-bus@1 {
+	compatible = "simple-bus";
+	ranges = <0x00 0x40000000  0x01 0x00 0x00000000  0x00 0x00400000>;
+	dma-ranges = <0x10 0x00000000  0x43000000 0x10 0x00000000  0x10 0x00000000>;
+	#address-cells = <2>;
+	#size-cells = <2>;
+
+	rp1_clocks: clocks@40018000 {
+		compatible = "raspberrypi,rp1-clocks";
+		reg = <0x00 0x40018000 0x0 0x10038>;
+		#clock-cells = <1>;
+		clocks = <&clk_rp1_xosc>;
+		assigned-clocks = <&rp1_clocks RP1_PLL_SYS_CORE>,
+				  <&rp1_clocks RP1_PLL_SYS>,
+				  <&rp1_clocks RP1_PLL_SYS_SEC>,
+				  <&rp1_clocks RP1_CLK_SYS>;
+		assigned-clock-rates = <1000000000>, // RP1_PLL_SYS_CORE
+				       <200000000>,  // RP1_PLL_SYS
+				       <125000000>,  // RP1_PLL_SYS_SEC
+				       <200000000>;  // RP1_CLK_SYS
+	};
+
+	rp1_gpio: pinctrl@400d0000 {
+		compatible = "raspberrypi,rp1-gpio";
+		reg = <0x00 0x400d0000  0x0 0xc000>,
+		      <0x00 0x400e0000  0x0 0xc000>,
+		      <0x00 0x400f0000  0x0 0xc000>;
+		gpio-controller;
+		#gpio-cells = <2>;
+		interrupt-controller;
+		#interrupt-cells = <2>;
+		interrupts = <0 IRQ_TYPE_LEVEL_HIGH>,
+			     <1 IRQ_TYPE_LEVEL_HIGH>,
+			     <2 IRQ_TYPE_LEVEL_HIGH>;
+	};
+};

new file mode 100644
index 000000000000..0ef30d7f1c35
@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: (GPL-2.0 OR MIT)
+
+rp1_nexus {
+	compatible = "pci1de4,1";
+	#address-cells = <3>;
+	#size-cells = <2>;
+	ranges = <0x01 0x00 0x00000000
+		  0x02000000 0x00 0x00000000
+		  0x0 0x400000>;
+	interrupt-controller;
+	#interrupt-cells = <2>;
+
+	#include "rp1-common.dtsi"
+};

2.35.3

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.

---
 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 +
 8 files changed, 387 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

index 6b37d61150ee..3b9606bb4ccc 100644
@@ -648,4 +648,5 @@ source "drivers/misc/uacce/Kconfig"
 source "drivers/misc/pvpanic/Kconfig"
 source "drivers/misc/mchp_pci1xxxx/Kconfig"
 source "drivers/misc/keba/Kconfig"
+source "drivers/misc/rp1/Kconfig"
 endmenu

index d6c917229c45..e15a732de690 100644
@@ -74,3 +74,4 @@ lan966x-pci-objs		:= lan966x_pci.o
 lan966x-pci-objs		+= lan966x_pci.dtbo.o
 obj-$(CONFIG_MCHP_LAN966X_PCI)	+= lan966x-pci.o
 obj-y				+= keba/
+obj-$(CONFIG_MISC_RP1)		+= rp1/

new file mode 100644
index 000000000000..5232e70d3079
@@ -0,0 +1,20 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# RaspberryPi RP1 misc device
+#
+
+config MISC_RP1
+	tristate "RaspberryPi RP1 misc device"
+	depends on OF_IRQ && OF_OVERLAY && PCI_MSI && PCI_QUIRKS
+	select PCI_DYNAMIC_OF_NODES
+	help
+	  Support the RP1 peripheral chip found on Raspberry Pi 5 board.
+
+	  This device supports several sub-devices including e.g. Ethernet
+	  controller, USB controller, I2C, SPI and UART.
+
+	  The driver is responsible for enabling the DT node once the PCIe
+	  endpoint has been configured, and handling interrupts.
+
+	  This driver uses an overlay to load other drivers to support for
+	  RP1 internal sub-devices.

new file mode 100644
index 000000000000..508b4cb05627
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_MISC_RP1)		+= rp1-pci.o
+rp1-pci-objs			:= rp1_pci.o rp1-pci.dtbo.o

new file mode 100644
index 000000000000..eea826b36e02
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: (GPL-2.0 OR MIT)
+
+/*
+ * The dts overlay is included from the dts directory so
+ * it can be possible to check it with CHECK_DTBS while
+ * also compile it from the driver source directory.
+ */
+
+/dts-v1/;
+/plugin/;
+
+/ {
+	fragment@0 {
+		target-path="";
+		__overlay__ {
+			compatible = "pci1de4,1";
+			#address-cells = <3>;
+			#size-cells = <2>;
+			interrupt-controller;
+			#interrupt-cells = <2>;
+
+			#include "arm64/broadcom/rp1-common.dtsi"
+		};
+	};
+};

index 8d610c17e0f2..dad0ca42707f 100644
@@ -6284,6 +6284,7 @@ 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

index 2e28182c3af0..ddfe09722d54 100644
@@ -2624,6 +2624,9 @@
 #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

The RP1 found on Raspberry Pi 5 board needs an external crystal at 50MHz. Add clk_rp1_xosc node to provide that.

---
 arch/arm64/boot/dts/broadcom/bcm2712-rpi-5-b.dts | 7 +++++++
 1 file changed, 7 insertions(+)

index fbc56309660f..1850a575e708 100644
@@ -16,6 +16,13 @@ chosen: chosen {
 		stdout-path = "serial10:115200n8";
 	};
 
+	clk_rp1_xosc: clock-50000000 {
+		compatible = "fixed-clock";
+		#clock-cells = <0>;
+		clock-output-names = "rp1-xosc";
+		clock-frequency = <50000000>;
+	};
+
 	/* Will be filled by the bootloader */
 	memory@0 {
 		device_type = "memory";

2.35.3

Add the fully populated DTS for RaspberryPi 5 which includes the RP1 node definition. The inclusion tree is as follow (the arrow points to the includer):

rp1-common.dtsi ----> rp1-nexus.dtsi ----> bcm2712-rpi-5-b.dts

                                               ^
                                               |
                                           bcm2712-rpi-5-b-ovl-rp1.dts

This is designed to maximize the compatibility with downstream DT while ensuring that a fully defined DT (one which includes the RP1 node as opposed to load it from overlay at runtime) is present since early boot stage.

Since the preferred board DT is the fully populated one, name it bcm2712-rpi-5-b.dts and move the previous one into bcm2712-rpi-5-b-ovl-rp1.dts.

---
 arch/arm64/boot/dts/broadcom/Makefile         |   1 +
 .../dts/broadcom/bcm2712-rpi-5-b-ovl-rp1.dts  | 121 ++++++++++++++++++
 .../boot/dts/broadcom/bcm2712-rpi-5-b.dts     | 118 ++---------------
 3 files changed, 133 insertions(+), 107 deletions(-)
 create mode 100644 arch/arm64/boot/dts/broadcom/bcm2712-rpi-5-b-ovl-rp1.dts

index 01ecfa304184..031875a277d7 100644
@@ -7,6 +7,7 @@ dtb-$(CONFIG_ARCH_BCM2835) += bcm2711-rpi-400.dtb \
 			      bcm2711-rpi-4-b.dtb \
 			      bcm2711-rpi-cm4-io.dtb \
 			      bcm2712-rpi-5-b.dtb \
+			      bcm2712-rpi-5-b-ovl-rp1.dtb \
 			      bcm2712-d-rpi-5-b.dtb \
 			      bcm2837-rpi-2-b.dtb \
 			      bcm2837-rpi-3-a-plus.dtb \

2.35.3

Define the RP1 node in an overlay. The inclusion tree is as follow (the arrow points to the includer):

                      rp1.dtso
                          ^
                          |

rp1-common.dtsi ----> rp1-nexus.dtsi

---
 arch/arm64/boot/dts/broadcom/Makefile |  3 ++-
 arch/arm64/boot/dts/broadcom/rp1.dtso | 11 +++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)
 create mode 100644 arch/arm64/boot/dts/broadcom/rp1.dtso

index 031875a277d7..83d45afc6588 100644
@@ -14,7 +14,8 @@ dtb-$(CONFIG_ARCH_BCM2835) += bcm2711-rpi-400.dtb \
 			      bcm2837-rpi-3-b.dtb \
 			      bcm2837-rpi-3-b-plus.dtb \
 			      bcm2837-rpi-cm3-io3.dtb \
-			      bcm2837-rpi-zero-2-w.dtb
+			      bcm2837-rpi-zero-2-w.dtb \
+			      rp1.dtbo
 
 subdir-y	+= bcmbca
 subdir-y	+= northstar2

new file mode 100644
index 000000000000..ab4f146d22c0
@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: (GPL-2.0 OR MIT)
+
+/dts-v1/;
+/plugin/;
+
+&pcie2 {
+	#address-cells = <3>;
+	#size-cells = <2>;
+
+	#include "rp1-nexus.dtsi"
+};

2.35.3

Select the RP1 drivers needed to operate the PCI endpoint containing several peripherals such as Ethernet and USB Controller. This chip is present on RaspberryPi 5.

---
 arch/arm64/configs/defconfig | 3 +++
 1 file changed, 3 insertions(+)

index 5bb8f09422a2..f6e9bb2a3578 100644
@@ -620,6 +620,7 @@ CONFIG_PINCTRL_QCS615=y
 CONFIG_PINCTRL_QCS8300=y
 CONFIG_PINCTRL_QDF2XXX=y
 CONFIG_PINCTRL_QDU1000=y
+CONFIG_PINCTRL_RP1=m
 CONFIG_PINCTRL_SA8775P=y
 CONFIG_PINCTRL_SC7180=y
 CONFIG_PINCTRL_SC7280=y

@@ -702,6 +703,7 @@ CONFIG_SENSORS_RASPBERRYPI_HWMON=m
 CONFIG_SENSORS_SL28CPLD=m
 CONFIG_SENSORS_INA2XX=m
 CONFIG_SENSORS_INA3221=m
+CONFIG_MISC_RP1=m
 CONFIG_THERMAL_GOV_POWER_ALLOCATOR=y
 CONFIG_CPU_THERMAL=y
 CONFIG_DEVFREQ_THERMAL=y

@@ -1299,6 +1301,7 @@ CONFIG_COMMON_CLK_CS2000_CP=y
 CONFIG_COMMON_CLK_FSL_SAI=y
 CONFIG_COMMON_CLK_S2MPS11=y
 CONFIG_COMMON_CLK_PWM=y
+CONFIG_COMMON_CLK_RP1=m
 CONFIG_COMMON_CLK_RS9_PCIE=y
 CONFIG_COMMON_CLK_VC3=y
 CONFIG_COMMON_CLK_VC5=y

2.35.3

The RP1 driver uses the infrastructure enabled by OF_OVERLAY config option. Enable that option in defconfig in order to produce a kernel usable on RaspberryPi5 avoiding to enable it separately.

---
 arch/arm64/configs/defconfig | 1 +
 1 file changed, 1 insertion(+)

index f6e9bb2a3578..ccf2f50673a3 100644
@@ -1659,6 +1659,7 @@ CONFIG_FPGA_BRIDGE=m
 CONFIG_ALTERA_FREEZE_BRIDGE=m
 CONFIG_FPGA_REGION=m
 CONFIG_OF_FPGA_REGION=m
+CONFIG_OF_OVERLAY=y
 CONFIG_TEE=y
 CONFIG_OPTEE=y
 CONFIG_MUX_GPIO=m

2.35.3

Raspberry Pi RP1 is a southbridge PCIe device which embeds several peripherals.
Add a new section to cover the main RP1 driver, DTS and specific subperipherals (such as clock and pinconf/pinmux/gpio controller).

---
 MAINTAINERS | 8 ++++++++
 1 file changed, 8 insertions(+)

index 2b16ba4eb1ce..2add073f5bdf 100644
@@ -20197,6 +20197,14 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/media/raspberrypi,rp1-cfe.yaml
 F:	drivers/media/platform/raspberrypi/rp1-cfe/
 
+RASPBERRY PI RP1 PCI DRIVER
+M:	Andrea della Porta <[email protected]>
+S:	Maintained
+F:	arch/arm64/boot/dts/broadcom/rp1*.dts*
+F:	drivers/clk/clk-rp1.c
+F:	drivers/misc/rp1/
+F:	drivers/pinctrl/pinctrl-rp1.c
+
 RC-CORE / LIRC FRAMEWORK
 M:	Sean Young <[email protected]>
 L:	[email protected]

2.35.3

Then it needs to be a new version, not the same one please.

thanks,

greg k-h

Sending V11 in a moment.

Thanks,
Andrea