On Mon, 27 Nov 2017 12:51:48 +0100 Arnd Bergmann arnd@arndb.de wrote:
getnstimeofday() suffers from the overflow in y2038 on 32-bit architectures and requires a conversion into the nanosecond format that we want here.
This changes ssp_parse_dataframe() to use ktime_get_real_ns() directly, which does not have that problem.
An open question is what time base should be used here. Normally timestamps should use ktime_get_ns() or ktime_get_boot_ns() to read monotonic time instead of "real" time, which suffers from time jumps due to settimeofday() calls or leap seconds.
Signed-off-by: Arnd Bergmann arnd@arndb.de
+cc Karol Wrona.
Fix looks fine to me, but might be nice to address that and the question of using a monotonic clock all in one go.
This is probably a copy of an ancient piece of my stupidity where I used the wrong clock for the core IIO timestamping code. We fixed that a while back by letting the user chose the clock. If you are running slow enough you actually do want the 'real' time - probably never the case here though.
If we don't hear from Karol for a few weeks I'll pick this up and we can address the wrong timestamp sometime in the future!
Jonathan
drivers/iio/common/ssp_sensors/ssp_spi.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/drivers/iio/common/ssp_sensors/ssp_spi.c b/drivers/iio/common/ssp_sensors/ssp_spi.c index 704284a475ae..2ab106bb3e03 100644 --- a/drivers/iio/common/ssp_sensors/ssp_spi.c +++ b/drivers/iio/common/ssp_sensors/ssp_spi.c @@ -277,12 +277,9 @@ static int ssp_handle_big_data(struct ssp_data *data, char *dataframe, int *idx) static int ssp_parse_dataframe(struct ssp_data *data, char *dataframe, int len) { int idx, sd;
- struct timespec ts; struct ssp_sensor_data *spd; struct iio_dev **indio_devs = data->sensor_devs;
- getnstimeofday(&ts);
- for (idx = 0; idx < len;) { switch (dataframe[idx++]) { case SSP_MSG2AP_INST_BYPASS_DATA:
@@ -329,7 +326,7 @@ static int ssp_parse_dataframe(struct ssp_data *data, char *dataframe, int len) } if (data->time_syncing)
data->timestamp = ts.tv_sec * 1000000000ULL + ts.tv_nsec;
data->timestamp = ktime_get_real_ns();return 0; }