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Date: Sun, 22 Mar 2020 15:54:55 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Lars-Peter Clausen <lars@...afoo.de>
Cc: Alexandru Tachici <tachicialex@...il.com>,
linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/4] iio: accel: adxl372: Add support for FIFO peak
mode
On Wed, 18 Mar 2020 11:10:10 +0100
Lars-Peter Clausen <lars@...afoo.de> wrote:
> On 3/18/20 12:09 PM, Alexandru Tachici wrote:
> > From: Stefan Popa <stefan.popa@...log.com>
> >
> > By default, if all three channels (x, y, z) are enabled, sample sets of
> > concurrent 3-axis data is stored in the FIFO. This patch adds the option
> > to configure the FIFO to store peak acceleration (x, y and z) of every
> > over-threshold event. When pushing to iio buffer we push only enabled
> > axis data.
> >
> > Signed-off-by: Stefan Popa <stefan.popa@...log.com>
> > ---
> > drivers/iio/accel/adxl372.c | 74 ++++++++++++++++++++++++++++++++++++-
> > 1 file changed, 73 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/iio/accel/adxl372.c b/drivers/iio/accel/adxl372.c
> > index 67b8817995c0..90c37d6f10d3 100644
> > --- a/drivers/iio/accel/adxl372.c
> > +++ b/drivers/iio/accel/adxl372.c
> > @@ -133,6 +133,9 @@
> >
> > /* The ADXL372 includes a deep, 512 sample FIFO buffer */
> > #define ADXL372_FIFO_SIZE 512
> > +#define ADXL372_X_AXIS_EN(x) (((x) >> 0) & 0x1)
> > +#define ADXL372_Y_AXIS_EN(x) (((x) >> 1) & 0x1)
> > +#define ADXL372_Z_AXIS_EN(x) (((x) >> 2) & 0x1)
> >
> > /*
> > * At +/- 200g with 12-bit resolution, scale is computed as:
> > @@ -253,6 +256,7 @@ struct adxl372_state {
> > struct iio_trigger *dready_trig;
> > enum adxl372_fifo_mode fifo_mode;
> > enum adxl372_fifo_format fifo_format;
> > + unsigned int fifo_axis_mask;
> > enum adxl372_op_mode op_mode;
> > enum adxl372_act_proc_mode act_proc_mode;
> > enum adxl372_odr odr;
> > @@ -264,6 +268,7 @@ struct adxl372_state {
> > u8 int2_bitmask;
> > u16 watermark;
> > __be16 fifo_buf[ADXL372_FIFO_SIZE];
> > + bool peak_fifo_mode_en;
> > };
> >
> > static const unsigned long adxl372_channel_masks[] = {
> > @@ -522,6 +527,22 @@ static int adxl372_get_status(struct adxl372_state *st,
> > return ret;
> > }
> >
> > +static void adxl372_arrange_axis_data(struct adxl372_state *st, __be16 *sample)
> > +{
> > + __be16 axis_sample[3];
> > + int i = 0;
> > +
> > + memset(axis_sample, 0, 3 * sizeof(__be16));
> > + if (ADXL372_X_AXIS_EN(st->fifo_axis_mask))
> > + axis_sample[i++] = sample[0];
> > + if (ADXL372_Y_AXIS_EN(st->fifo_axis_mask))
> > + axis_sample[i++] = sample[1];
> > + if (ADXL372_Z_AXIS_EN(st->fifo_axis_mask))
> > + axis_sample[i++] = sample[2];
> > +
> > + memcpy(sample, axis_sample, 3 * sizeof(__be16));
> > +}
> > +
> > static irqreturn_t adxl372_trigger_handler(int irq, void *p)
> > {
> > struct iio_poll_func *pf = p;
> > @@ -553,8 +574,12 @@ static irqreturn_t adxl372_trigger_handler(int irq, void *p)
> > goto err;
> >
> > /* Each sample is 2 bytes */
> > - for (i = 0; i < fifo_entries; i += st->fifo_set_size)
> > + for (i = 0; i < fifo_entries; i += st->fifo_set_size) {
> > + /* filter peak detection data */
> > + if (st->peak_fifo_mode_en)
> > + adxl372_arrange_axis_data(st, &st->fifo_buf[i]);
> > iio_push_to_buffers(indio_dev, &st->fifo_buf[i]);
> > + }
> > }
> > err:
> > iio_trigger_notify_done(indio_dev->trig);
> > @@ -722,6 +747,43 @@ static int adxl372_write_raw(struct iio_dev *indio_dev,
> > }
> > }
> >
> > +static ssize_t adxl372_peak_fifo_en_get(struct device *dev,
> > + struct device_attribute *attr,
> > + char *buf)
> > +{
> > + struct adxl372_state *st = iio_priv(dev_to_iio_dev(dev));
> > +
> > + return sprintf(buf, "%d\n", st->peak_fifo_mode_en);
> > +}
> > +
> > +static ssize_t adxl372_peak_fifo_en_set(struct device *dev,
> > + struct device_attribute *attr,
> > + const char *buf, size_t len)
> > +{
> > + struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> > + struct adxl372_state *st = iio_priv(indio_dev);
> > + bool val;
> > + int ret;
> > +
> > + ret = iio_device_claim_direct_mode(indio_dev);
> > + if (ret < 0)
> > + return ret;
> > +
> > + ret = kstrtobool(buf, &val);
> > + if (ret)
> > + return ret;
> > +
> > + st->peak_fifo_mode_en = val;
> > +
> > + iio_device_release_direct_mode(indio_dev);
> > +
> > + return len;
> > +}
> > +
> > +static IIO_DEVICE_ATTR(hwfifo_peak_mode_enable, 0644,
> > + adxl372_peak_fifo_en_get,
> > + adxl372_peak_fifo_en_set, 0);
> > +
>
> Rather than going with a non-standard attribute, I'd register a IIO
> trigger for the peak mode and switch between peak and normal mode by
> assigning the corresponding trigger.
>
> At least that's how I understand how this mode works. Data capture is
> triggered by exceeding a threshold.
I wondered about that, but my reading of the datasheet suggests this isn't
simply a trigger that runs when data is above a threshold but rather
specifically the highest value that occurs between crossing the threshold
on the way up and crossing it again on the way down.
We could still consider it a trigger though, be it a very strange one.
There is another mode where it moves out of lower power mode into
high power mode at the first crossing of a threshold. That one I can't
see how to implement as a trigger type really as it wouldn't jump back
into low power mode without some form of user intervention.
Confusing device...
Jonathan
>
> - Lars
>
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