Kernel: Improve the aarch64 kernel source files disk layout

Kernel/Arch/aarch64/RPi/MMIO.h

@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2021, Nico Weber <thakis@chromium.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Types.h>
+
+namespace Prekernel {
+
+// Knows about memory-mapped IO addresses on the Broadcom family of SOCs used in Raspberry Pis.
+// RPi3 is the first Raspberry Pi that supports aarch64.
+// https://github.com/raspberrypi/documentation/files/1888662/BCM2837-ARM-Peripherals.-.Revised.-.V2-1.pdf (RPi3)
+// https://datasheets.raspberrypi.org/bcm2711/bcm2711-peripherals.pdf (RPi4 Model B)
+class MMIO {
+public:
+    static MMIO& the();
+
+    u32 read(FlatPtr offset) { return *peripheral_address(offset); }
+    void write(FlatPtr offset, u32 value) { *peripheral_address(offset) = value; }
+
+    u32 volatile* peripheral_address(FlatPtr offset) { return (u32 volatile*)(m_base_address + offset); }
+    template<class T>
+    T volatile* peripheral(FlatPtr offset) { return (T volatile*)peripheral_address(offset); }
+
+    FlatPtr peripheral_base_address() const { return m_base_address; }
+    FlatPtr peripheral_end_address() const { return m_base_address + 0x00FFFFFF; }
+
+private:
+    MMIO();
+
+    unsigned int m_base_address;
+};
+
+}