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greybus: loopback: handle timestamp roll-over

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This patch ensures we account for roll-over in the loopback driver.
do_gettimeofday() is used to grab a timestamp. Two timestamps are derived
one before and one after a gb_operation_sync(), however since
do_gettimeofday() returns the number of seconds and mircoseconds that have
elapsed today - we need to account for a situation where the timestamp
starts at say 23:59:999us rolls over and the end time is now earlier than
the start time.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
This commit is contained in:
Bryan O'Donoghue 2015-08-11 13:50:54 +01:00 committed by Greg Kroah-Hartman
parent 4c192665f0
commit fd489e1ac6
1 changed files with 6 additions and 1 deletions
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7
drivers/staging/greybus/loopback.c
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@ -22,6 +22,8 @@
#include "greybus.h"
#define NSEC_PER_DAY 86400000000000ULL
struct gb_loopback_stats {
u32 min;
u32 max;
@ -226,7 +228,10 @@ static void gb_loopback_calc_latency(struct gb_loopback *gb,
t1 = timeval_to_ns(ts);
t2 = timeval_to_ns(te);
gb->elapsed_nsecs = t2 - t1;
if (t2 > t1)
gb->elapsed_nsecs = t2 - t1;
else
gb->elapsed_nsecs = NSEC_PER_DAY - t2 + t1;
}
static int gb_loopback_sink(struct gb_loopback *gb, u32 len)