x86: TSC: define the PIT latch value separate

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

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 346cae5ac4237b5602d04910edd4a2f43fab36af..aa11413e7c1d271a4a2f54a5f707b5ffe6271324 100644 (file)
--- 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;
 }