On Mon, 27 Nov 2017 12:51:48 +0100
Arnd Bergmann <a...@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 <a...@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;
> }
