[PATCH] hpet: use read_timer_tsc only when CPU has TSC

Only use read_timer_tsc only when CPU has TSC.  Thanks to Andrea for
pointing this out.  Should not be issue on any platforms as all recent
systems that has HPET also has CPUs that supports TSC.  The patch is still
required for correctness.
Signed-off-by: NVenkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

arch/i386/kernel/timers/timer_hpet.c

@@ -136,6 +136,8 @@ static void delay_hpet(unsigned long loops)
 	} while ((hpet_end - hpet_start) < (loops));
 }
 
+static struct timer_opts timer_hpet;
+
 static int __init init_hpet(char* override)
 {
 	unsigned long result, remain;
@@ -163,6 +165,8 @@ static int __init init_hpet(char* override)
 			}
 			set_cyc2ns_scale(cpu_khz/1000);
 		}
+		/* set this only when cpu_has_tsc */
+		timer_hpet.read_timer = read_timer_tsc;
 	}
 
 	/*
@@ -186,7 +190,6 @@ static struct timer_opts timer_hpet __read_mostly = {
 	.get_offset =		get_offset_hpet,
 	.monotonic_clock =	monotonic_clock_hpet,
 	.delay = 		delay_hpet,
-	.read_timer = 		read_timer_tsc,
 };
 
 struct init_timer_opts __initdata timer_hpet_init = {