patch-2.2.0-pre2 linux/include/asm-alpha/delay.h

• Lines: 71
• Date: Tue Dec 29 13:56:15 1998
• Orig file: v2.2.0-pre1/linux/include/asm-alpha/delay.h
• Orig date: Fri May 8 23:14:54 1998

diff -u --recursive --new-file v2.2.0-pre1/linux/include/asm-alpha/delay.h linux/include/asm-alpha/delay.h
@@ -1,7 +1,7 @@
 #ifndef __ALPHA_DELAY_H
 #define __ALPHA_DELAY_H
 
-extern unsigned long loops_per_sec;
+#include <asm/smp.h>
 
 /*
  * Copyright (C) 1993 Linus Torvalds
@@ -9,7 +9,8 @@
  * Delay routines, using a pre-computed "loops_per_second" value.
  */
 
-extern __inline__ void __delay(unsigned long loops)
+extern __inline__ void
+__delay(unsigned long loops)
 {
 	__asm__ __volatile__(".align 3\n"
 		"1:\tsubq %0,1,%0\n\t"
@@ -24,15 +25,46 @@
  * lookup table, really, as the multiplications take much too long with
  * short delays.  This is a "reasonable" implementation, though (and the
  * first constant multiplications gets optimized away if the delay is
- * a constant)
+ * a constant).
+ *
+ * Optimize small constants further by exposing the second multiplication
+ * to the compiler.  In addition, mulq is 2 cycles faster than umulh.
  */
-extern __inline__ void udelay(unsigned long usecs)
+
+extern __inline__ void
+__udelay(unsigned long usecs, unsigned long lps)
 {
+	/* compute (usecs * 2**64 / 10**6) * loops_per_sec / 2**64 */
+
 	usecs *= 0x000010c6f7a0b5edUL;		/* 2**64 / 1000000 */
-	__asm__("umulh %1,%2,%0"
-		:"=r" (usecs)
-		:"r" (usecs),"r" (loops_per_sec));
+	__asm__("umulh %1,%2,%0" :"=r" (usecs) :"r" (usecs),"r" (lps));
+	__delay(usecs);
+}
+
+extern __inline__ void
+__small_const_udelay(unsigned long usecs, unsigned long lps)
+{
+	/* compute (usecs * 2**32 / 10**6) * loops_per_sec / 2**32 */
+
+        usecs *= 0x10c6;                /* 2^32 / 10^6 */
+	usecs *= lps;
+	usecs >>= 32;
 	__delay(usecs);
 }
+
+#ifdef __SMP__
+#define udelay(usecs)						\
+	(__builtin_constant_p(usecs) && usecs < 0x100000000UL	\
+	 ? __small_const_udelay(usecs,				\
+		cpu_data[smp_processor_id()].loops_per_sec)	\
+	 : __udelay(usecs,					\
+		cpu_data[smp_processor_id()].loops_per_sec))
+#else
+#define udelay(usecs)						\
+	(__builtin_constant_p(usecs) && usecs < 0x100000000UL	\
+	 ? __small_const_udelay(usecs, loops_per_sec)		\
+	 : __udelay(usecs, loops_per_sec))
+#endif
+
 
 #endif /* defined(__ALPHA_DELAY_H) */