Kernel/aarch64: Use a platform init function for most of the RPi code

This required making the `debug_output` console configurable at runtime
by introducing a `DebugConsole` struct, which simply contains a callback
for printing a single character.
We should probably use something like this abstraction for all
architectures in the future.

Kernel/Arch/aarch64/DebugOutput.cpp

@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2024, Sönke Holz <sholz8530@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <Kernel/Arch/aarch64/DebugOutput.h>
+
+namespace Kernel {
+
+static DebugConsole const* s_debug_console;
+
+void set_debug_console(DebugConsole const* debug_console)
+{
+    s_debug_console = debug_console;
+}
+
+void debug_output(char character)
+{
+    if (s_debug_console != nullptr)
+        s_debug_console->write_character(character);
+}
+
+}

Kernel/Arch/aarch64/DebugOutput.h

@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) 2024, Sönke Holz <sholz8530@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <Kernel/Arch/DebugOutput.h>
+
+namespace Kernel {
+
+struct DebugConsole {
+    void (*write_character)(char);
+};
+
+void set_debug_console(DebugConsole const*);
+
+}

Kernel/Arch/aarch64/PlatformInit.h

@@ -0,0 +1,15 @@
+/*
+ * Copyright (c) 2024, Sönke Holz <sholz8530@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/StringView.h>
+
+namespace Kernel {
+
+void raspberry_pi_platform_init(StringView compatible_string);
+
+}

Kernel/Arch/aarch64/PlatformInit/RaspberryPi.cpp

@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2021, Nico Weber <thakis@chromium.org>
+ * Copyright (c) 2024, Sönke Holz <sholz8530@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <Kernel/Arch/aarch64/PlatformInit.h>
+
+#include <Kernel/Arch/aarch64/DebugOutput.h>
+#include <Kernel/Arch/aarch64/RPi/Framebuffer.h>
+#include <Kernel/Arch/aarch64/RPi/GPIO.h>
+#include <Kernel/Arch/aarch64/RPi/Mailbox.h>
+#include <Kernel/Arch/aarch64/RPi/Timer.h>
+#include <Kernel/Arch/aarch64/RPi/UART.h>
+
+namespace Kernel {
+
+void raspberry_pi_platform_init(StringView)
+{
+    static DebugConsole const s_debug_console {
+        .write_character = [](char character) {
+            RPi::UART::the().send(character);
+        },
+    };
+
+    RPi::Mailbox::initialize();
+    RPi::GPIO::initialize();
+    RPi::UART::initialize();
+
+    constexpr int baud_rate = 115'200;
+
+    // Set UART clock so that the baud rate divisor ends up as 1.0.
+    // FIXME: Not sure if this is a good UART clock rate.
+    u32 rate_in_hz = RPi::Timer::set_clock_rate(RPi::Timer::ClockID::UART, 16 * baud_rate);
+
+    // The BCM's PL011 UART is alternate function 0 on pins 14 and 15.
+    auto& gpio = RPi::GPIO::the();
+    gpio.set_pin_function(14, RPi::GPIO::PinFunction::Alternate0);
+    gpio.set_pin_function(15, RPi::GPIO::PinFunction::Alternate0);
+    gpio.set_pin_pull_up_down_state(Array { 14, 15 }, RPi::GPIO::PullUpDownState::Disable);
+
+    // Clock and pins are configured. Turn UART on.
+    RPi::UART::the().set_baud_rate(baud_rate, rate_in_hz);
+
+    set_debug_console(&s_debug_console);
+
+    auto firmware_version = RPi::Mailbox::the().query_firmware_version();
+    dmesgln("RPi: Firmware version: {}", firmware_version);
+
+    RPi::Framebuffer::initialize();
+}
+
+}

Kernel/Arch/aarch64/RPi/DebugOutput.cpp

@@ -1,20 +0,0 @@
-/*
- * Copyright (c) 2022, Liav A. <liavalb@hotmail.co.il>
- *
- * SPDX-License-Identifier: BSD-2-Clause
- */
-
-#include <Kernel/Arch/DebugOutput.h>
-#include <Kernel/Arch/aarch64/RPi/UART.h>
-
-namespace Kernel {
-
-void debug_output(char ch)
-{
-    if (!Memory::MemoryManager::is_initialized())
-        return;
-
-    RPi::UART::the().send(ch);
-}
-
-}

Kernel/Arch/aarch64/RPi/GPIO.cpp

@@ -38,15 +38,27 @@ struct GPIOControlRegisters {
     u32 test;
 };
 
+static Singleton<GPIO> s_the;
+
 GPIO::GPIO()
     : m_registers(MMIO::the().peripheral<GPIOControlRegisters>(0x20'0000).release_value_but_fixme_should_propagate_errors())
 {
 }
 
+void GPIO::initialize()
+{
+    s_the.ensure_instance();
+}
+
+bool GPIO::is_initialized()
+{
+    return s_the.is_initialized();
+}
+
 GPIO& GPIO::the()
 {
-    static Singleton<GPIO> instance;
-    return instance;
+    VERIFY(is_initialized());
+    return s_the;
 }
 
 void GPIO::set_pin_function(unsigned pin_number, PinFunction function)

Kernel/Arch/aarch64/RPi/GPIO.h

@@ -30,6 +30,8 @@ public:
         Alternate5 = 0b010,
     };
 
+    static void initialize();
+    static bool is_initialized();
     static GPIO& the();
 
     void set_pin_function(unsigned pin_number, PinFunction);

Kernel/Arch/aarch64/RPi/Mailbox.cpp

@@ -38,6 +38,8 @@ constexpr u32 MBOX_EMPTY = 0x4000'0000;
 
 constexpr int ARM_TO_VIDEOCORE_CHANNEL = 8;
 
+static Singleton<Mailbox> s_the;
+
 Mailbox::Mailbox()
     : m_registers(MMIO::the().peripheral<MailboxRegisters>(0xb880).release_value_but_fixme_should_propagate_errors())
 {
@@ -61,10 +63,20 @@ bool Mailbox::MessageHeader::success() const
     return m_command_tag == MBOX_RESPONSE_SUCCESS;
 }
 
+void Mailbox::initialize()
+{
+    s_the.ensure_instance();
+}
+
+bool Mailbox::is_initialized()
+{
+    return s_the.is_initialized();
+}
+
 Mailbox& Mailbox::the()
 {
-    static Singleton<Mailbox> instance;
-    return instance;
+    VERIFY(is_initialized());
+    return s_the;
 }
 
 void Mailbox::wait_until_we_can_write() const

Kernel/Arch/aarch64/RPi/Mailbox.h

@@ -51,6 +51,8 @@ public:
         u32 m_empty_tag = 0;
     };
 
+    static void initialize();
+    static bool is_initialized();
     static Mailbox& the();
 
     // Sends message queue to VideoCore

Kernel/Arch/aarch64/RPi/UART.cpp

@@ -5,9 +5,7 @@
  */
 
 #include <AK/Singleton.h>
-#include <Kernel/Arch/aarch64/RPi/GPIO.h>
 #include <Kernel/Arch/aarch64/RPi/MMIO.h>
-#include <Kernel/Arch/aarch64/RPi/Timer.h>
 #include <Kernel/Arch/aarch64/RPi/UART.h>
 
 namespace Kernel::RPi {
@@ -90,6 +88,8 @@ enum ControlBits {
     CTSHardwareFlowControlEnable = 1 << 15,
 };
 
+static Singleton<UART> s_the;
+
 UART::UART()
     : m_registers(MMIO::the().peripheral<UARTRegisters>(0x20'1000).release_value_but_fixme_should_propagate_errors())
 {
@@ -98,29 +98,25 @@ UART::UART()
 
     // FIXME: Should wait for current transmission to end and should flush FIFO.
 
-    constexpr int baud_rate = 115'200;
-
-    // Set UART clock so that the baud rate divisor ends up as 1.0.
-    // FIXME: Not sure if this is a good UART clock rate.
-    u32 rate_in_hz = Timer::set_clock_rate(Timer::ClockID::UART, 16 * baud_rate);
-
-    // The BCM's PL011 UART is alternate function 0 on pins 14 and 15.
-    auto& gpio = GPIO::the();
-    gpio.set_pin_function(14, GPIO::PinFunction::Alternate0);
-    gpio.set_pin_function(15, GPIO::PinFunction::Alternate0);
-    gpio.set_pin_pull_up_down_state(Array { 14, 15 }, GPIO::PullUpDownState::Disable);
-
-    // Clock and pins are configured. Turn UART on.
-    set_baud_rate(baud_rate, rate_in_hz);
     m_registers->line_control = EnableFIFOs | WordLength8Bits;
 
     m_registers->control = UARTEnable | TransmitEnable | ReceiveEnable;
 }
 
+void UART::initialize()
+{
+    s_the.ensure_instance();
+}
+
+bool UART::is_initialized()
+{
+    return s_the.is_initialized();
+}
+
 UART& UART::the()
 {
-    static Singleton<UART> instance;
-    return instance;
+    VERIFY(is_initialized());
+    return s_the;
 }
 
 void UART::send(u32 c)

Kernel/Arch/aarch64/RPi/UART.h

@@ -19,6 +19,8 @@ struct UARTRegisters;
 class UART {
 public:
     UART();
+    static void initialize();
+    static bool is_initialized();
     static UART& the();
 
     void send(u32 c);
@@ -26,8 +28,9 @@ public:
 
     void print_str(char const*, size_t);
 
-private:
     void set_baud_rate(int baud_rate, int uart_frequency_in_hz);
+
+private:
     void wait_until_we_can_send();
     void wait_until_we_can_receive();
 

Kernel/Arch/init.cpp

@@ -198,13 +198,6 @@ extern "C" [[noreturn]] UNMAP_AFTER_INIT NO_SANITIZE_COVERAGE void init([[maybe_
     DeviceTree::run_platform_init();
 #endif
 
-#if ARCH(AARCH64)
-    auto firmware_version = RPi::Mailbox::the().query_firmware_version();
-    dmesgln("RPi: Firmware version: {}", firmware_version);
-
-    RPi::Framebuffer::initialize();
-#endif
-
     // NOTE: If the bootloader provided a framebuffer, then set up an initial console.
     // If the bootloader didn't provide a framebuffer, then set up an initial text console.
     // We do so we can see the output on the screen as soon as possible.

Kernel/CMakeLists.txt

@@ -473,7 +473,6 @@ if ("${SERENITY_ARCH}" STREQUAL "x86_64")
 elseif("${SERENITY_ARCH}" STREQUAL "aarch64")
     set(RPI_SOURCES
         Arch/aarch64/RPi/AUX.cpp
-        Arch/aarch64/RPi/DebugOutput.cpp
         Arch/aarch64/RPi/Framebuffer.cpp
         Arch/aarch64/RPi/GPIO.cpp
         Arch/aarch64/RPi/InterruptController.cpp
@@ -503,6 +502,7 @@ elseif("${SERENITY_ARCH}" STREQUAL "aarch64")
         Arch/aarch64/boot.S
         Arch/aarch64/CPUID.cpp
         Arch/aarch64/CurrentTime.cpp
+        Arch/aarch64/DebugOutput.cpp
         Arch/aarch64/Dummy.cpp
         Arch/aarch64/FPUState.S
         Arch/aarch64/InterruptManagement.cpp
@@ -514,6 +514,8 @@ elseif("${SERENITY_ARCH}" STREQUAL "aarch64")
         Arch/aarch64/SafeMem.cpp
         Arch/aarch64/SmapDisabler.cpp
         Arch/aarch64/vector_table.S
+
+        Arch/aarch64/PlatformInit/RaspberryPi.cpp
     )
 
     # Otherwise linker errors e.g undefined reference to `__aarch64_cas8_acq_rel'

Kernel/Firmware/DeviceTree/PlatformInit.cpp

@@ -10,6 +10,10 @@
 #include <Kernel/Firmware/DeviceTree/PlatformInit.h>
 #include <LibDeviceTree/FlattenedDeviceTree.h>
 
+#if ARCH(AARCH64)
+#    include <Kernel/Arch/aarch64/PlatformInit.h>
+#endif
+
 namespace Kernel::DeviceTree {
 
 struct PlatformInitTableEntry {
@@ -17,7 +21,12 @@ struct PlatformInitTableEntry {
     void (*init_function)(StringView compatible_string);
 };
 
-static constinit auto const s_platform_init_table = to_array<PlatformInitTableEntry>({});
+static constinit auto const s_platform_init_table = to_array<PlatformInitTableEntry>({
+#if ARCH(AARCH64)
+    { "raspberrypi,3-model-b"sv, raspberry_pi_platform_init },
+    { "raspberrypi,4-model-b"sv, raspberry_pi_platform_init },
+#endif
+});
 
 void run_platform_init()
 {