1 files changed, 66 insertions, 0 deletions

diff --git a/include/asm-ppc/delay.h b/include/asm-ppc/delay.h
new file mode 100644
index 000000000000..badde6845af2
--- /dev/null
+++ b/include/asm-ppc/delay.h
@@ -0,0 +1,66 @@
+#ifdef __KERNEL__
+#ifndef _PPC_DELAY_H
+#define _PPC_DELAY_H
+
+#include <asm/param.h>
+
+/*
+ * Copyright 1996, Paul Mackerras.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+extern unsigned long loops_per_jiffy;
+
+extern void __delay(unsigned int loops);
+
+/*
+ * Note that 19 * 226 == 4294 ==~ 2^32 / 10^6, so
+ * loops = (4294 * usecs * loops_per_jiffy * HZ) / 2^32.
+ *
+ * The mulhwu instruction gives us loops = (a * b) / 2^32.
+ * We choose a = usecs * 19 * HZ and b = loops_per_jiffy * 226
+ * because this lets us support a wide range of HZ and
+ * loops_per_jiffy values without either a or b overflowing 2^32.
+ * Thus we need usecs * HZ <= (2^32 - 1) / 19 = 226050910 and
+ * loops_per_jiffy <= (2^32 - 1) / 226 = 19004280
+ * (which corresponds to ~3800 bogomips at HZ = 100).
+ *  -- paulus
+ */
+#define __MAX_UDELAY    (226050910UL/HZ)        /* maximum udelay argument */
+#define __MAX_NDELAY    (4294967295UL/HZ)       /* maximum ndelay argument */
+
+extern __inline__ void __udelay(unsigned int x)
+{
+        unsigned int loops;
+
+        __asm__("mulhwu %0,%1,%2" : "=r" (loops) :
+                "r" (x), "r" (loops_per_jiffy * 226));
+        __delay(loops);
+}
+
+extern __inline__ void __ndelay(unsigned int x)
+{
+        unsigned int loops;
+
+        __asm__("mulhwu %0,%1,%2" : "=r" (loops) :
+                "r" (x), "r" (loops_per_jiffy * 5));
+        __delay(loops);
+}
+
+extern void __bad_udelay(void);         /* deliberately undefined */
+extern void __bad_ndelay(void);         /* deliberately undefined */
+
+#define udelay(n) (__builtin_constant_p(n)? \
+        ((n) > __MAX_UDELAY? __bad_udelay(): __udelay((n) * (19 * HZ))) : \
+        __udelay((n) * (19 * HZ)))
+
+#define ndelay(n) (__builtin_constant_p(n)? \
+        ((n) > __MAX_NDELAY? __bad_ndelay(): __ndelay((n) * HZ)) : \
+        __ndelay((n) * HZ))
+
+#endif /* defined(_PPC_DELAY_H) */
+#endif /* __KERNEL__ */