[PATCH 2/4] clock: Update cs->cycle_last when switching clock

[Jules Maselbas]

If clocksource is free-running it might have been running for a while
before barebox started, we only care about the time spent in barebox.
We can discard the cycles accumulated before switching clocks by
updating cs->cycle_last with the cycles read for the new clock right
before switching.

Signed-off-by: Jules Maselbas <jmaselbas at kalray.eu>
---
 common/clock.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/common/clock.c b/common/clock.c
index 58c2964b1..e30c81a37 100644
--- a/common/clock.c
+++ b/common/clock.c
@@ -222,6 +222,12 @@ int init_clock(struct clocksource *cs)
 			return ret;
 	}
 
+	/*
+	 * If clocksource is freerunning it might have been running for a while
+	 * before barebox started, we only care about the time spent in barebox
+	 * thus we must discard the clocksource cycles up to this exact moment:
+	 */
+	cs->cycle_last = cs->read() & cs->mask;
 	current_clock = cs;
 	time_beginning = get_time_ns();
 
-- 
2.17.1