[PATCH] commands: uptime: add note about caveats

Ahmad Fatoum a.fatoum at pengutronix.de
Wed Nov 2 01:50:17 PDT 2022

Normally timer overrun is not that much of a problem, because there
where it matters, we usually have an is_timeout() in the loop that reads
the timer often enough. This doesn't necessarily hold for the new uptime
command and basically anything can happen between subsequent calls and
if get_time_ns() is not called often enough during that time, we end up
with an inaccurate uptime. Mention this in the extended help text.

Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
Can be squashed into original commit.
 commands/uptime.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/commands/uptime.c b/commands/uptime.c
index a9a8c650b698..d67538631c8f 100644
--- a/commands/uptime.c
+++ b/commands/uptime.c
@@ -66,6 +66,9 @@ static int do_uptime(int argc, char *argv[])
 BAREBOX_CMD_HELP_TEXT("This command formats the number of elapsed nanoseconds")
 BAREBOX_CMD_HELP_TEXT("as measured with the current clocksource")
+BAREBOX_CMD_HELP_TEXT("Note: Timekeeping is co-operative. If long running code does")
+BAREBOX_CMD_HELP_TEXT("not use delay/is_timeout/get_time_ns/getchar functions")
+BAREBOX_CMD_HELP_TEXT("timer may overrun resulting in incorrect results")
 BAREBOX_CMD_HELP_OPT ("-n",     "output elapsed time in nanoseconds")

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