On Sat, 2 Dec 2017 11:49:49 +0000
Jonathan Cameron <jic23@xxxxxxxxxx> wrote:
> On Mon, 27 Nov 2017 12:51:48 +0100
> Arnd Bergmann <arnd@xxxxxxxx> 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@xxxxxxxx>
>
> +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;
> > }
>
> --
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