[PATCH] time_interpolator: Use readq_relaxed() instead of readq().

On some platforms readq performs additional work to make sure I/O is done
in a coherent way.  This is not needed for time retrieval as done by the
time interpolator.  So we can use readq_relaxed instead which will improve
performance.

It affects sparc64 and ia64 only.  Apparently it makes a significant
difference on ia64.

Signed-off-by: Christoph Lameter <[email protected]>
Cc: john stultz <[email protected]>
Cc: "David S. Miller" <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

kernel/timer.c

@@ -1351,10 +1351,10 @@ static inline u64 time_interpolator_get_cycles(unsigned int src)
 			return x();
 
 		case TIME_SOURCE_MMIO64	:
-			return readq((void __iomem *) time_interpolator->addr);
+			return readq_relaxed((void __iomem *)time_interpolator->addr);
 
 		case TIME_SOURCE_MMIO32	:
-			return readl((void __iomem *) time_interpolator->addr);
+			return readl_relaxed((void __iomem *)time_interpolator->addr);
 
 		default: return get_cycles();
 	}