x86: TSC: define the PIT latch value separate

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 9 insertions, 5 deletions

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 346cae5ac423..aa11413e7c1d 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -122,6 +122,10 @@ static u64 tsc_read_refs(u64 *pm, u64 *hpet)
         return ULLONG_MAX;
 }
 
+#define CAL_MS          50
+#define CAL_LATCH       (CLOCK_TICK_RATE / (1000 / CAL_MS))
+#define CAL_PIT_LOOPS   5000
+
 /*
  * Try to calibrate the TSC against the Programmable
  * Interrupt Timer and return the frequency of the TSC
@@ -144,8 +148,8 @@ static unsigned long pit_calibrate_tsc(void)
          * (LSB then MSB) to begin countdown.
          */
         outb(0xb0, 0x43);
-        outb((CLOCK_TICK_RATE / (1000 / 50)) & 0xff, 0x42);
-        outb((CLOCK_TICK_RATE / (1000 / 50)) >> 8, 0x42);
+        outb(CAL_LATCH & 0xff, 0x42);
+        outb(CAL_LATCH >> 8, 0x42);
 
         tsc = t1 = t2 = get_cycles();
 
@@ -166,18 +170,18 @@ static unsigned long pit_calibrate_tsc(void)
         /*
          * Sanity checks:
          *
-         * If we were not able to read the PIT more than 5000
+         * If we were not able to read the PIT more than PIT_MIN_LOOPS
          * times, then we have been hit by a massive SMI
          *
          * If the maximum is 10 times larger than the minimum,
          * then we got hit by an SMI as well.
          */
-        if (pitcnt < 5000 || tscmax > 10 * tscmin)
+        if (pitcnt < CAL_PIT_LOOPS || tscmax > 10 * tscmin)
                 return ULONG_MAX;
 
         /* Calculate the PIT value */
         delta = t2 - t1;
-        do_div(delta, 50);
+        do_div(delta, CAL_MS);
         return delta;
 }