[PATCH 1/3] mull'ify multiplication with HZ in __const_udelay() [Was: Re: Too much error in __const_udelay() ?]

[Dominik Brodowski]

Move the multiplication of (loops_per_jiffy * xloops) with HZ into
the "mull" asm operation. This increases the accuracy of the delay functions
largely:

n usec delay on a 1500000 BogoMIPS system: 

  n 	   before	  after
  1	 1000 ticks	 1499 ticks
 10	14000 ticks	14999 ticks

n usec delay on a 100000 BogoMIPS system: 

 n 	   before	  after
  1	    0 ticks	   99 ticks
 10	    0 ticks	  999 ticks
100	 9000 ticks	 9999 ticks


Signed-off-by: Dominik Brodowski <linux@xxxxxxxx>


diff -ruN linux-original/arch/i386/lib/delay.c linux/arch/i386/lib/delay.c
--- linux-original/arch/i386/lib/delay.c	2004-06-07 22:01:46.608351088 +0200
+++ linux/arch/i386/lib/delay.c	2004-06-07 22:05:03.299449496 +0200
@@ -33,8 +33,8 @@
 	int d0;
 	__asm__("mull %0"
 		:"=d" (xloops), "=&a" (d0)
-		:"1" (xloops),"0" (current_cpu_data.loops_per_jiffy));
-        __delay(xloops * HZ);
+		:"1" (xloops),"0" (current_cpu_data.loops_per_jiffy * HZ));
+        __delay(xloops);
 }
 
 void __udelay(unsigned long usecs)
-
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