* [PATCH] iio: common: ssp_sensors: use ktime_get_real_ns() timestamps
@ 2017-11-27 11:51 Arnd Bergmann
2017-12-02 11:49 ` Jonathan Cameron
0 siblings, 1 reply; 3+ messages in thread
From: Arnd Bergmann @ 2017-11-27 11:51 UTC (permalink / raw)
To: Jonathan Cameron, Arnd Bergmann
Cc: y2038, Hartmut Knaack, Lars-Peter Clausen,
Peter Meerwald-Stadler, linux-iio, linux-kernel
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(-)
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;
}
--
2.9.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] iio: common: ssp_sensors: use ktime_get_real_ns() timestamps
2017-11-27 11:51 [PATCH] iio: common: ssp_sensors: use ktime_get_real_ns() timestamps Arnd Bergmann
@ 2017-12-02 11:49 ` Jonathan Cameron
2017-12-10 15:03 ` Jonathan Cameron
0 siblings, 1 reply; 3+ messages in thread
From: Jonathan Cameron @ 2017-12-02 11:49 UTC (permalink / raw)
To: Arnd Bergmann
Cc: y2038, Hartmut Knaack, Lars-Peter Clausen,
Peter Meerwald-Stadler, linux-iio, linux-kernel, k.wrona
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;
> }
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] iio: common: ssp_sensors: use ktime_get_real_ns() timestamps
2017-12-02 11:49 ` Jonathan Cameron
@ 2017-12-10 15:03 ` Jonathan Cameron
0 siblings, 0 replies; 3+ messages in thread
From: Jonathan Cameron @ 2017-12-10 15:03 UTC (permalink / raw)
To: Arnd Bergmann
Cc: y2038, Hartmut Knaack, Lars-Peter Clausen,
Peter Meerwald-Stadler, linux-iio, linux-kernel, k.wrona
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;
> > }
>
> --
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^ permalink raw reply [flat|nested] 3+ messages in thread
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2017-11-27 11:51 [PATCH] iio: common: ssp_sensors: use ktime_get_real_ns() timestamps Arnd Bergmann
2017-12-02 11:49 ` Jonathan Cameron
2017-12-10 15:03 ` Jonathan Cameron
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