Re: [PATCH v4 5/6] iio:bmi160: use iio_pollfunc_store_time

[Jonathan Cameron <jic23@kernel.org>]

On Sat,  2 Feb 2019 13:56:00 -0800
Martin Kelly <martin@martingkelly.com> wrote:

> From: Martin Kelly <martin@martingkelly.com>
> 
> Currently, we snap the timestamp after reading from the buffer and
> processing the event. When the IIO poll function is triggered by an
> interrupt,  we can get a slightly more accurate timestamp by snapping it
> prior to reading the data, since the data was already generated prior to
> entering the trigger handler. This is not going to make a huge difference,
> but we might as well improve slightly.
> 
> Do this by using iio_pollfunc_store_time as other drivers do.
> 
> Signed-off-by: Martin Kelly <martin@martingkelly.com>
There is one small quirk here I'd forgotten about, but seems unlikely to
cause too many problems.  There are triggers that only call
iio_trigger_poll_chained (which is badly named) and as a result
only end up calling the thread part.  That would result in no
timestamp.

It's a hole we really ought to figure out a reliable fix for that
effects lots of drivers.

Anyhow, I doubt anyone is using this device with that set of triggers
so should be fine whilst we think about a more general solution.

Applied to the togreg branch of iio.git and pushed out as testing
for the autobuilders to play with it.

Thanks,

Jonathan


> ---
>  drivers/iio/imu/bmi160/bmi160_core.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iio/imu/bmi160/bmi160_core.c b/drivers/iio/imu/bmi160/bmi160_core.c
> index 007f7c532ac4..f3c5b86a281e 100644
> --- a/drivers/iio/imu/bmi160/bmi160_core.c
> +++ b/drivers/iio/imu/bmi160/bmi160_core.c
> @@ -425,8 +425,7 @@ static irqreturn_t bmi160_trigger_handler(int irq, void *p)
>  		buf[j++] = sample;
>  	}
>  
> -	iio_push_to_buffers_with_timestamp(indio_dev, buf,
> -					   iio_get_time_ns(indio_dev));
> +	iio_push_to_buffers_with_timestamp(indio_dev, buf, pf->timestamp);
>  done:
>  	iio_trigger_notify_done(indio_dev->trig);
>  	return IRQ_HANDLED;
> @@ -834,7 +833,8 @@ int bmi160_core_probe(struct device *dev, struct regmap *regmap,
>  	indio_dev->modes = INDIO_DIRECT_MODE;
>  	indio_dev->info = &bmi160_info;
>  
> -	ret = devm_iio_triggered_buffer_setup(dev, indio_dev, NULL,
> +	ret = devm_iio_triggered_buffer_setup(dev, indio_dev,
> +					      iio_pollfunc_store_time,
>  					      bmi160_trigger_handler, NULL);
>  	if (ret < 0)
>  		return ret;