Re: [PATCH v3 1/4] iio: accel: adxl372: Add support for FIFO peak mode

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On 3/18/20 12:09 PM, Alexandru Tachici wrote:
From: Stefan Popa <stefan.popa@xxxxxxxxxx>

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@xxxxxxxxxx>
---
  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.

- Lars




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