| Message ID | 20171127115158.2884398-1-arnd@arndb.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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; > } -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Sat, 2 Dec 2017 11:49:49 +0000 Jonathan Cameron <jic23@kernel.org> wrote: > 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! > Applied to the togreg branch of iio.git and pushed out as testing for the autobuilders to play with it. Thanks, Jonathan > 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; > > } > > -- > To unsubscribe from this list: send the line "unsubscribe linux-iio" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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; }
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> --- drivers/iio/common/ssp_sensors/ssp_spi.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-)