timekeeping: Consolidate fast timekeeper

Provide a inline function which replaces the copy & pasta.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220415091921.072296632@linutronix.de

kernel/time/timekeeping.c

@@ -429,6 +429,14 @@ static void update_fast_timekeeper(const struct tk_read_base *tkr,
 	memcpy(base + 1, base, sizeof(*base));
 }
 
+static __always_inline u64 fast_tk_get_delta_ns(struct tk_read_base *tkr)
+{
+	u64 delta, cycles = tk_clock_read(tkr);
+
+	delta = clocksource_delta(cycles, tkr->cycle_last, tkr->mask);
+	return timekeeping_delta_to_ns(tkr, delta);
+}
+
 static __always_inline u64 __ktime_get_fast_ns(struct tk_fast *tkf)
 {
 	struct tk_read_base *tkr;
@@ -439,12 +447,7 @@ static __always_inline u64 __ktime_get_fast_ns(struct tk_fast *tkf)
 		seq = raw_read_seqcount_latch(&tkf->seq);
 		tkr = tkf->base + (seq & 0x01);
 		now = ktime_to_ns(tkr->base);
-
-		now += timekeeping_delta_to_ns(tkr,
-				clocksource_delta(
-					tk_clock_read(tkr),
-					tkr->cycle_last,
-					tkr->mask));
+		now += fast_tk_get_delta_ns(tkr);
 	} while (read_seqcount_latch_retry(&tkf->seq, seq));
 
 	return now;
@@ -560,10 +563,7 @@ static __always_inline u64 __ktime_get_real_fast(struct tk_fast *tkf, u64 *mono)
 		tkr = tkf->base + (seq & 0x01);
 		basem = ktime_to_ns(tkr->base);
 		baser = ktime_to_ns(tkr->base_real);
-
-		delta = timekeeping_delta_to_ns(tkr,
-				clocksource_delta(tk_clock_read(tkr),
-				tkr->cycle_last, tkr->mask));
+		delta = fast_tk_get_delta_ns(tkr);
 	} while (read_seqcount_latch_retry(&tkf->seq, seq));
 
 	if (mono)