Merge tag 'iio-fixes-for-5.15a' of https://git.kernel.org/pub/scm/linux/kernel/git...

[platform/kernel/linux-rpi.git] / kernel / time / tick-internal.h

diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h
index 3548f08..649f2b4 100644 (file)
--- a/kernel/time/tick-internal.h
+++ b/kernel/time/tick-internal.h
@@ -177,3 +177,23 @@ void clock_was_set(unsigned int bases);
 void clock_was_set_delayed(void);
 
 void hrtimers_resume_local(void);
+
+/* Since jiffies uses a simple TICK_NSEC multiplier
+ * conversion, the .shift value could be zero. However
+ * this would make NTP adjustments impossible as they are
+ * in units of 1/2^.shift. Thus we use JIFFIES_SHIFT to
+ * shift both the nominator and denominator the same
+ * amount, and give ntp adjustments in units of 1/2^8
+ *
+ * The value 8 is somewhat carefully chosen, as anything
+ * larger can result in overflows. TICK_NSEC grows as HZ
+ * shrinks, so values greater than 8 overflow 32bits when
+ * HZ=100.
+ */
+#if HZ < 34
+#define JIFFIES_SHIFT  6
+#elif HZ < 67
+#define JIFFIES_SHIFT  7
+#else
+#define JIFFIES_SHIFT  8
+#endif