1 files changed, 73 insertions, 0 deletions
diff --git a/kernel/include/util/delay.h b/kernel/include/util/delay.h
new file mode 100644
index 0000000..29cf3b2
--- /dev/null
+++ b/kernel/include/util/delay.h
@@ -0,0 +1,73 @@
+#pragma once
+
+#include "types.h"
+#include "util/debug.h"
+
+/* Approximate numbers taken from various points in Linux kernel */
+#define LOOPS_PER_JIFFY (1 << 12)
+#define HZ 100 /* Found this in a random place in the kernel */
+
+/* From arch/x86/lib/delay.c in Linux kernel */
+/*
+ *      Precise Delay Loops for i386
+ *
+ *      Copyright (C) 1993 Linus Torvalds
+ *      Copyright (C) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
+ *      Copyright (C) 2008 Jiri Hladky <hladky _dot_ jiri _at_ gmail _dot_ com>
+ *
+ *      The __delay function must _NOT_ be inlined as its execution time
+ *      depends wildly on alignment on many x86 processors. The additional
+ *      jump magic is needed to get the timing stable on all the CPU's
+ *      we have to worry about.
+ */
+
+static void __delay(unsigned long loops)
+{
+    __asm__ volatile(
+        "	test %0,%0	\n"
+        "	jz 3f		\n"
+        "	jmp 1f		\n"
+
+        ".align 16		\n"
+        "1:	jmp 2f		\n"
+
+        ".align 16		\n"
+        "2:	dec %0		\n"
+        "	jnz 2b		\n"
+        "3:	dec %0		\n"
+
+        : /* we don't need output */
+        : "a"(loops));
+}
+
+static inline void __const_udelay(unsigned long xloops)
+{
+    int d0;
+
+    xloops *= 4;
+    __asm__ volatile("mull %%edx"
+                     : "=d"(xloops), "=&a"(d0)
+                     : "1"(xloops), "0"(LOOPS_PER_JIFFY * (HZ / 4)));
+
+    __delay(++xloops);
+}
+
+static inline void __udelay(unsigned long usecs)
+{
+    __const_udelay(usecs * 4295); /* 2**32 / 1000000 */
+}
+
+static inline void __ndelay(unsigned long nsecs)
+{
+    __const_udelay(nsecs * 5); /* 2**32 / 1000000000 */
+}
+
+#define udelay(n)                                                       \
+    (__builtin_constant_p(n) ? ((n) > 20000 ? panic("Delay too large!") \
+                                            : __const_udelay((n)*4295)) \
+                             : __udelay(n))
+
+#define ndelay(n)                                                            \
+    (__builtin_constant_p(n)                                                 \
+         ? ((n) > 20000 ? panic("Delay too large!") : __const_udelay((n)*5)) \
+         : __ndelay(n))