[AGPGART] Make AGP depend on PCI

[pandora-kernel.git] / arch / i386 / kernel / timers / timer_hpet.c

diff --git a/arch/i386/kernel/timers/timer_hpet.c b/arch/i386/kernel/timers/timer_hpet.c
index d973a8b..17a6fe7 100644 (file)
--- a/arch/i386/kernel/timers/timer_hpet.c
+++ b/arch/i386/kernel/timers/timer_hpet.c
@@ -30,23 +30,28 @@ static seqlock_t monotonic_lock = SEQLOCK_UNLOCKED;
  *  basic equation:
  *             ns = cycles / (freq / ns_per_sec)
  *             ns = cycles * (ns_per_sec / freq)
- *             ns = cycles * (10^9 / (cpu_mhz * 10^6))
- *             ns = cycles * (10^3 / cpu_mhz)
+ *             ns = cycles * (10^9 / (cpu_khz * 10^3))
+ *             ns = cycles * (10^6 / cpu_khz)
  *
  *     Then we use scaling math (suggested by george@mvista.com) to get:
- *             ns = cycles * (10^3 * SC / cpu_mhz) / SC
+ *             ns = cycles * (10^6 * SC / cpu_khz) / SC
  *             ns = cycles * cyc2ns_scale / SC
  *
  *     And since SC is a constant power of two, we can convert the div
  *  into a shift.
+ *
+ *  We can use khz divisor instead of mhz to keep a better percision, since
+ *  cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
+ *  (mathieu.desnoyers@polymtl.ca)
+ *
  *                     -johnstul@us.ibm.com "math is hard, lets go shopping!"
  */
-static unsigned long cyc2ns_scale;
+static unsigned long cyc2ns_scale __read_mostly;
 #define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
 
-static inline void set_cyc2ns_scale(unsigned long cpu_mhz)
+static inline void set_cyc2ns_scale(unsigned long cpu_khz)
 {
-       cyc2ns_scale = (1000 << CYC2NS_SCALE_FACTOR)/cpu_mhz;
+       cyc2ns_scale = (1000000 << CYC2NS_SCALE_FACTOR)/cpu_khz;
 }
 
 static inline unsigned long long cycles_2_ns(unsigned long long cyc)
@@ -163,7 +168,7 @@ static int __init init_hpet(char* override)
                                printk("Detected %u.%03u MHz processor.\n",
                                        cpu_khz / 1000, cpu_khz % 1000);
                        }
-                       set_cyc2ns_scale(cpu_khz/1000);
+                       set_cyc2ns_scale(cpu_khz);
                }
                /* set this only when cpu_has_tsc */
                timer_hpet.read_timer = read_timer_tsc;