clocksource: keep track of original clocksource frequency

[mv-sheeva.git] / include / linux / clocksource.h

diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 55e434feec993d9656ccf6bcd31964005daa9667..f0a7fb9844138132f8a22a4e5cc27e31b64ed3a4 100644 (file)
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -45,7 +45,8 @@ struct clocksource;
  * @read:              returns a cycle value
  * @mask:              bitmask for two's complement
  *                     subtraction of non 64 bit counters
- * @mult:              cycle to nanosecond multiplier
+ * @mult:              cycle to nanosecond multiplier (adjusted by NTP)
+ * @mult_orig:         cycle to nanosecond multiplier (unadjusted by NTP)
  * @shift:             cycle to nanosecond divisor (power of two)
  * @flags:             flags describing special properties
  * @vread:             vsyscall based read
@@ -63,6 +64,7 @@ struct clocksource {
        cycle_t (*read)(void);
        cycle_t mask;
        u32 mult;
+       u32 mult_orig;
        u32 shift;
        unsigned long flags;
        cycle_t (*vread)(void);
@@ -201,16 +203,17 @@ static inline void clocksource_calculate_interval(struct clocksource *c,
 {
        u64 tmp;
 
-       /* XXX - All of this could use a whole lot of optimization */
+       /* Do the ns -> cycle conversion first, using original mult */
        tmp = length_nsec;
        tmp <<= c->shift;
-       tmp += c->mult/2;
-       do_div(tmp, c->mult);
+       tmp += c->mult_orig/2;
+       do_div(tmp, c->mult_orig);
 
        c->cycle_interval = (cycle_t)tmp;
        if (c->cycle_interval == 0)
                c->cycle_interval = 1;
 
+       /* Go back from cycles -> shifted ns, this time use ntp adjused mult */
        c->xtime_interval = (u64)c->cycle_interval * c->mult;
 }