WIP arm64 arch_cpu.cpp

Still needs work, opted to have arch files in tree to share
the burden of the port

src/system/boot/arch/arm64/arch_cpu.cpp

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2021, Haiku, Inc. All rights reserved.
+ * Distributed under the terms of the MIT License.
+ *
+ */
+
+#include <OS.h>
+#include <boot/platform.h>
+/*
+#include <boot/stdio.h>
+#include <boot/kernel_args.h>
+#include <boot/stage2.h>
+#include <arch/cpu.h>
+#include <arch_kernel.h>
+#include <arch_system_info.h>
+#include <string.h>
+*/
+
+extern "C" status_t
+boot_arch_cpu_init(void)
+{
+	return B_OK;
+}
+
+
+extern "C" void
+arch_ucode_load(BootVolume& volume)
+{
+	// Yes, we have no bananas!
+}
+
+
+extern "C" bigtime_t
+system_time()
+{
+
+	#warning Implement system_time in ARM64 bootloader!
+	//https://en.wikipedia.org/wiki/Time_Stamp_Counter
+	// read system time register:  cntpct_el0 / cntvct_el0
+	// frequency of the system timer can be discovered by reading cntfrq_el0
+	// https://wiki.osdev.org/ARMv7_Generic_Timers#CNTPCT
+
+	uint64_t ticks;
+	__asm__ volatile("mrs %0, cntpct_el0" : "=r"(ticks));
+	//conversion factor stuff
+	return ticks;
+	//return u64_mul_u64_fp32_64(ticks, ns_per_cntpct);
+}
+
+
+extern "C" void
+spin(bigtime_t microseconds)
+{
+	auto time = system_time();
+
+	while ((system_time() - time) < microseconds)
+		asm volatile ("yield;");
+}