On Sun, 17 Nov 2024 18:26:50 +0000
Lothar Rubusch <l.rubusch@gmail.com> wrote:
> Pause the measurement while reading fifo values. Initially an interrupt
> is triggered if watermark of the FIFO is reached, or in case of
> OVERRUN. The sensor stays mute until FIFO is cleared and interrupts are
> read. Situations now can arise when the watermark is configured to a
> lower value. While reading the values, new values arrive such that a
> permanent OVERRUN state of the FIFO is reached, i.e. either the FIFO
> never gets emptied entirely because of permanently new arriving
> measurements. No more interrupts will be issued and the setup results
> in OVERRUN. To avoid such situation, stop measuring while solving an
> OVERRUN condition and generally reading FIFO entries.
Whilst solving overrun it makes sense. Whilst dealing with a watermark
interrupt not so much. The whole point of those is to allow capture
of data without missing samples. We should continue to acquire data
during the readback.
>
> Signed-off-by: Lothar Rubusch <l.rubusch@gmail.com>
> ---
> drivers/iio/accel/adxl345_core.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/drivers/iio/accel/adxl345_core.c b/drivers/iio/accel/adxl345_core.c
> index 07c336211f..c79f0f5e3b 100644
> --- a/drivers/iio/accel/adxl345_core.c
> +++ b/drivers/iio/accel/adxl345_core.c
> @@ -730,6 +730,11 @@ static irqreturn_t adxl345_trigger_handler(int irq, void *p)
>
> if (int_stat & (ADXL345_INT_DATA_READY | ADXL345_INT_WATERMARK)) {
> pr_debug("%s(): WATERMARK or DATA_READY event detected\n", __func__);
> +
> + /* Pause measuring, at low watermarks this would easily brick the
> + * sensor in permanent OVERRUN state
> + */
> + adxl345_set_measure_en(st, false);
> if (adxl345_get_fifo_entries(st, &fifo_entries) < 0)
> goto err;
>
> @@ -737,12 +742,15 @@ static irqreturn_t adxl345_trigger_handler(int irq, void *p)
> goto err;
>
> iio_trigger_notify_done(indio_dev->trig);
> + adxl345_set_measure_en(st, true);
> }
>
> goto done;
> err:
> iio_trigger_notify_done(indio_dev->trig);
> + adxl345_set_measure_en(st, false);
> adxl345_empty_fifo(st);
> + adxl345_set_measure_en(st, true);
> return IRQ_NONE;
>
> done: