[ARM] 2871/1: Fixes an issue with gettimeofday not working correctly …

…on Intel IOP3xx processors

Patch from Adam Brooks

The current gettimeofday implementation for the IOP3xx processors reads the contents of the timer interrupt register and does math on the value to figure out exactly what time it is.  To do this it  multiplies the contents of the timer register with a large constant.  The result is then divided by a large constant.  Unfortunately the result of the first multiplication is often too large for the register to hold.  The solution is to combine the two large constants to a single smaller constant at compile time.  Then the timer value can be divided by single smaller constant without any overflow issues.

Signed-off-by: Adam Brooks <adam.j.brooks@intel.com>
Signed-off-by: Deepak Saxena <dsaxena@plexity.net>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mach-iop3xx/iop321-time.c

@@ -60,7 +60,7 @@ static unsigned long iop321_gettimeoffset(void)
 	/*
 	 * Now convert them to usec.
 	 */
-	usec = (unsigned long)(elapsed * (tick_nsec / 1000)) / LATCH;
+	usec = (unsigned long)(elapsed / (CLOCK_TICK_RATE/1000000));
 
 	return usec;
 }

arch/arm/mach-iop3xx/iop331-time.c

@@ -58,7 +58,7 @@ static unsigned long iop331_gettimeoffset(void)
 	/*
 	 * Now convert them to usec.
 	 */
-	usec = (unsigned long)(elapsed * (tick_nsec / 1000)) / LATCH;
+	usec = (unsigned long)(elapsed / (CLOCK_TICK_RATE/1000000));
 
 	return usec;
 }