Kernel/Net: Support the GEM ethernet adapter in the RP1

This means we now have ethernet support on the Raspberry Pi 5!
The generic Cadence Gigabit Ethernet MAC (GEM) driver only supports the
IP revision built into the RP1 for now, which is 1p09 according to the
datasheet.

Since the RP1 datasheet doesn't provide any detailed documentation about
this IP block, I referenced the AMD Zynq UltraScale+ docs,
as those devices also use the Cadence GEM (but a different version).

Author: spholz

Kernel/Arch/aarch64/RPi/RP1/GEM.cpp

@@ -0,0 +1,62 @@
+/*
+ * Copyright (c) 2026, Sönke Holz <soenke.holz@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <Kernel/Arch/aarch64/RPi/RP1/GEM.h>
+#include <Kernel/Arch/aarch64/RPi/RP1/RP1.h>
+#include <Kernel/Firmware/DeviceTree/DeviceTree.h>
+#include <Kernel/Net/Cadence/GEMRegisters.h>
+
+namespace Kernel::RPi {
+
+ErrorOr<NonnullRefPtr<RP1GEMNetworkAdapter>> RP1GEMNetworkAdapter::create(RP1& rp1, StringView interface_name, PhysicalAddress paddr, InterruptNumber interrupt_number)
+{
+    auto registers_mapping = TRY(Memory::map_typed_writable<CadenceGEMNetworkAdapter::Registers volatile>(paddr));
+
+    MACAddress mac_address;
+
+    // Since this isn't a devicetree driver, we unfortunately have to hardcode this absolute path here
+    // and hope that none of these node names will be different in future firmware updates.
+    auto mac_addr_prop = DeviceTree::get().resolve_property("/axi/pcie@1000120000/rp1/ethernet@100000/local-mac-address"sv);
+    if (mac_addr_prop.has_value() && mac_addr_prop->size() == 6) {
+        mac_address = MACAddress { mac_addr_prop->as<Array<u8, 6>>() };
+    } else {
+        dmesgln("Failed to retrieve RP1 GEM MAC address from the devicetree");
+        // TODO: We could fall back to a random MAC address here.
+        return EINVAL;
+    }
+
+    auto adapter = TRY(adopt_nonnull_ref_or_enomem(new (nothrow) RP1GEMNetworkAdapter(rp1, interface_name, mac_address, move(registers_mapping), interrupt_number)));
+    TRY(adapter->initialize());
+
+    return adapter;
+}
+
+RP1GEMNetworkAdapter::RP1GEMNetworkAdapter(RP1& rp1, StringView interface_name, MACAddress mac_address, Memory::TypedMapping<CadenceGEMNetworkAdapter::Registers volatile> registers, InterruptNumber interrupt_number)
+    : CadenceGEMNetworkAdapter(interface_name, mac_address, move(registers))
+    , m_rp1(rp1)
+    , m_interrupt_number(interrupt_number)
+{
+}
+
+void RP1GEMNetworkAdapter::register_and_enable_interrupt()
+{
+    // 6.2. MSIx configuration registers
+    // "The only true edge-level interrupts in RP1 are the set of vectors assigned to USBHOST0 and USBHOST1."
+    // So the ethernet controller has a level-triggered interrupt.
+    m_rp1.register_interrupt_handler(m_interrupt_number, RP1::InterruptTriggerMode::Level, [this](InterruptNumber) {
+        return handle_interrupt();
+    });
+}
+
+u32 RP1GEMNetworkAdapter::mdio_clock_input_frequency()
+{
+    // The MDC clock divider uses clk_sys as the input clock on the RP1. clk_sys runs at 200 MHz by default.
+    // FIXME: Ideally, we should derive clock routing from the devicetree, which would require some
+    //        generic infrastructure for devicetree clocks.
+    return 200'000'000;
+}
+
+}

Kernel/Arch/aarch64/RPi/RP1/GEM.h

@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2026, Sönke Holz <soenke.holz@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <Kernel/Interrupts/Interrupts.h>
+#include <Kernel/Net/Cadence/GEM.h>
+
+namespace Kernel::RPi {
+
+class RP1;
+
+class RP1GEMNetworkAdapter final : public CadenceGEMNetworkAdapter {
+public:
+    static ErrorOr<NonnullRefPtr<RP1GEMNetworkAdapter>> create(RP1&, StringView interface_name, PhysicalAddress, InterruptNumber);
+
+private:
+    RP1GEMNetworkAdapter(RP1&, StringView interface_name, MACAddress, Memory::TypedMapping<CadenceGEMNetworkAdapter::Registers volatile>, InterruptNumber);
+
+    virtual void register_and_enable_interrupt() override;
+    virtual u32 mdio_clock_input_frequency() override;
+
+    RP1& m_rp1;
+    InterruptNumber m_interrupt_number { 0 };
+};
+
+}

Kernel/Arch/aarch64/RPi/RP1/RP1.cpp

@@ -6,6 +6,7 @@
 
 #include <Kernel/Arch/aarch64/RPi/RP1/Clocks.h>
 #include <Kernel/Arch/aarch64/RPi/RP1/Fan.h>
+#include <Kernel/Arch/aarch64/RPi/RP1/GEM.h>
 #include <Kernel/Arch/aarch64/RPi/RP1/GPIO.h>
 #include <Kernel/Arch/aarch64/RPi/RP1/PWM.h>
 #include <Kernel/Arch/aarch64/RPi/RP1/RP1.h>
@@ -17,6 +18,7 @@
 #include <Kernel/Bus/USB/USBManagement.h>
 #include <Kernel/Firmware/DeviceTree/DeviceTree.h>
 #include <Kernel/Library/Panic.h>
+#include <Kernel/Net/NetworkingManagement.h>
 
 // https://datasheets.raspberrypi.com/rp1/rp1-peripherals.pdf
 
@@ -53,6 +55,8 @@ ErrorOr<void> RP1::initialize()
     enable_irq();
     enable_pin_based_interrupts();
 
+    // All interrupt numbers are taken from the devicetree.
+
     // Section 2.5. Clocks
     auto clocks = TRY(RP1Clocks::create(*this, bar1_address.offset(0x1'8000)));
 
@@ -64,14 +68,19 @@ ErrorOr<void> RP1::initialize()
 
     if (!kernel_command_line().disable_usb()) {
         // Chapter 5. USB
-        // The interrupt numbers are taken from the devicetree.
         auto usbhost0 = TRY(RP1xHCIController::try_to_initialize(*this, bar1_address.offset(0x20'0000), 0, 31));
         auto usbhost1 = TRY(RP1xHCIController::try_to_initialize(*this, bar1_address.offset(0x30'0000), 1, 36));
 
         USB::USBManagement::the().add_controller(usbhost0);
         USB::USBManagement::the().add_controller(usbhost1);
     }
 
+    // Chapter 7. Ethernet
+    auto gem_interface_name = TRY(NetworkingManagement::generate_interface_name_from_pci_address(device_identifier()));
+    auto gem = TRY(RP1GEMNetworkAdapter::create(*this, gem_interface_name.representable_view(), bar1_address.offset(0x10'0000), 6));
+
+    NetworkingManagement::the().register_adapter(gem).release_value_but_fixme_should_propagate_errors();
+
     auto cooling_fan_status = DeviceTree::get().resolve_property("/cooling_fan/status"sv);
     if (cooling_fan_status.has_value() && cooling_fan_status->as_string() == "okay"sv) {
         auto fan = TRY(RP1Fan::create(*this, gpio, pwm1));

Kernel/CMakeLists.txt

@@ -285,6 +285,7 @@ set(KERNEL_SOURCES
     Library/KLexicalPath.cpp
     Library/KString.cpp
     Library/UserOrKernelBuffer.cpp
+    Net/Cadence/GEM.cpp
     Net/Intel/E1000NetworkAdapter.cpp
     Net/Realtek/RTL8168NetworkAdapter.cpp
     Net/VirtIO/VirtIONetworkAdapter.cpp
@@ -484,6 +485,7 @@ elseif("${SERENITY_ARCH}" STREQUAL "aarch64")
         Arch/aarch64/RPi/MiniUART.cpp
         Arch/aarch64/RPi/RP1/Clocks.cpp
         Arch/aarch64/RPi/RP1/Fan.cpp
+        Arch/aarch64/RPi/RP1/GEM.cpp
         Arch/aarch64/RPi/RP1/GPIO.cpp
         Arch/aarch64/RPi/RP1/PWM.cpp
         Arch/aarch64/RPi/RP1/RP1.cpp