[PATCH v5 10/10] iio: accel: adxl345: add FIFO with watermark events

Lothar Rubusch
2024-12-05T17:14:07Z

Add a basic setup for FIFO with configurable watermark. Add a handler
for watermark interrupt events and extend the channel for the
scan_index needed for the iio channel. The sensor is configurable to use
a FIFO_BYPASSED mode or a FIFO_STREAM mode. For the FIFO_STREAM mode now
a watermark can be configured, or disabled by setting 0. Further features
require a working FIFO setup.

Signed-off-by: Lothar Rubusch <l.rubusch@gmail.com>
---
drivers/iio/accel/adxl345_core.c | 300 +++++++++++++++++++++++++++++++
1 file changed, 300 insertions(+)

diff --git a/drivers/iio/accel/adxl345_core.c b/drivers/iio/accel/adxl345_core.c
index 3067a70c54e..58ed82d66dc 100644
--- a/drivers/iio/accel/adxl345_core.c
+++ b/drivers/iio/accel/adxl345_core.c
@@ -15,15 +15,28 @@

#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/events.h>
+#include <linux/iio/kfifo_buf.h>

#include "adxl345.h"

+#define ADXL345_FIFO_BYPASS 0
+#define ADXL345_FIFO_FIFO 1
+#define ADXL345_FIFO_STREAM 2
+
+#define ADXL345_DIRS 3
+
struct adxl345_state {
int irq;
const struct adxl345_chip_info *info;
struct regmap *regmap;
+ __le16 fifo_buf[ADXL345_DIRS * ADXL345_FIFO_SIZE];
bool fifo_delay; /* delay: delay is needed for SPI */
u8 intio;
+ u8 int_map;
+ u8 watermark;
+ u8 fifo_mode;
};

#define ADXL345_CHANNEL(index, reg, axis) { \
@@ -36,6 +49,13 @@ struct adxl345_state {
.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) | \
BIT(IIO_CHAN_INFO_SAMP_FREQ), \
.scan_index = (index), \
+ .scan_type = { \
+ .sign = 's', \
+ .realbits = 13, \
+ .storagebits = 16, \
+ .shift = 0, \
+ .endianness = IIO_LE, \
+ }, \
}

enum adxl345_chans {
@@ -48,6 +68,25 @@ static const struct iio_chan_spec adxl345_channels[] = {
ADXL345_CHANNEL(2, chan_z, Z),
};

+static int adxl345_set_interrupts(struct adxl345_state *st)
+{
+ int ret;
+ unsigned int int_enable = st->int_map;
+ unsigned int int_map;
+
+ /* Any bits set to 0 in the INT map register send their respective
+ * interrupts to the INT1 pin, whereas bits set to 1 send their respective
+ * interrupts to the INT2 pin. The intio shall convert this accordingly.
+ */
+ int_map = 0xFF & (st->intio ? st->int_map : ~st->int_map);
+
+ ret = regmap_write(st->regmap, ADXL345_REG_INT_MAP, int_map);
+ if (ret)
+ return ret;
+
+ return regmap_write(st->regmap, ADXL345_REG_INT_ENABLE, int_enable);
+}
+
static int adxl345_read_raw(struct iio_dev *indio_dev,
struct iio_chan_spec const *chan,
int *val, int *val2, long mask)
@@ -133,6 +172,31 @@ static int adxl345_write_raw(struct iio_dev *indio_dev,
return -EINVAL;
}

+static int adxl345_set_watermark(struct iio_dev *indio_dev, unsigned int value)
+{
+ struct adxl345_state *st = iio_priv(indio_dev);
+ unsigned int fifo_mask = 0x1F;
+ int ret;
+
+ if (value == 0) {
+ st->int_map &= ~ADXL345_INT_WATERMARK;
+ return 0;
+ }
+
+ if (value > ADXL345_FIFO_SIZE)
+ value = ADXL345_FIFO_SIZE;
+
+ ret = regmap_update_bits(st->regmap, ADXL345_REG_FIFO_CTL,
+ fifo_mask, value);
+ if (ret)
+ return ret;
+
+ st->watermark = value;
+ st->int_map |= ADXL345_INT_WATERMARK;
+
+ return 0;
+}
+
static int adxl345_write_raw_get_fmt(struct iio_dev *indio_dev,
struct iio_chan_spec const *chan,
long mask)
@@ -188,11 +252,224 @@ static const struct attribute_group adxl345_attrs_group = {
.attrs = adxl345_attrs,
};

+static int adxl345_set_fifo(struct adxl345_state *st)
+{
+ u8 fifo_ctl;
+ int ret;
+
+ /* FIFO should only be configured while in standby mode */
+ ret = adxl345_set_measure_en(st, false);
+ if (ret < 0)
+ return ret;
+
+ fifo_ctl = ADXL345_FIFO_CTL_SAMLPES(st->watermark) |
+ ADXL345_FIFO_CTL_TRIGGER(st->intio) |
+ ADXL345_FIFO_CTL_MODE(st->fifo_mode);
+
+ ret = regmap_write(st->regmap, ADXL345_REG_FIFO_CTL, fifo_ctl);
+ if (ret < 0)
+ return ret;
+
+ return adxl345_set_measure_en(st, true);
+}
+
+/**
+ * adxl345_get_samples() - Read number of FIFO entries.
+ * @st: The initialized state instance of this driver.
+ *
+ * The sensor does not support treating any axis individually, or exclude them
+ * from measuring.
+ *
+ * Return: negative error, or value.
+ */
+static int adxl345_get_samples(struct adxl345_state *st)
+{
+ unsigned int regval = 0;
+ int ret;
+
+ ret = regmap_read(st->regmap, ADXL345_REG_FIFO_STATUS, &regval);
+ if (ret < 0)
+ return ret;
+
+ return 0x3f & regval;
+}
+
+/**
+ * adxl345_fifo_transfer() - Read samples number of elements.
+ * @st: The instance of the state object of this sensor.
+ * @samples: The number of lines in the FIFO referred to as fifo_entry,
+ * a fifo_entry has 3 elements for X, Y and Z direction of 2 bytes each.
+ *
+ * It is recommended that a multiple-byte read of all registers be performed to
+ * prevent a change in data between reads of sequential registers. That is to
+ * read out the data registers X0, X1, Y0, Y1, Z0, Z1 at once.
+ *
+ * Return: 0 or error value.
+ */
+static int adxl345_fifo_transfer(struct adxl345_state *st, int samples)
+{
+ size_t count;
+ int i, ret;
+
+ count = sizeof(st->fifo_buf[0]) * ADXL345_DIRS;
+ for (i = 0; i < samples; i++) {
+ ret = regmap_noinc_read(st->regmap, ADXL345_REG_XYZ_BASE,
+ st->fifo_buf + (i * count / 2), count);
+ if (ret < 0)
+ return ret;
+ }
+ return ret;
+}
+
+/**
+ * adxl345_fifo_reset() - Empty the FIFO in error condition.
+ * @st: The instance to the state object of the sensor.
+ *
+ * Read all elements of the FIFO. Reading the interrupt source register
+ * resets the sensor.
+ */
+static void adxl345_fifo_reset(struct adxl345_state *st)
+{
+ int regval;
+ int samples;
+
+ adxl345_set_measure_en(st, false);
+
+ samples = adxl345_get_samples(st);
+ if (samples > 0)
+ adxl345_fifo_transfer(st, samples);
+
+ regmap_read(st->regmap, ADXL345_REG_INT_SOURCE, &regval);
+
+ adxl345_set_measure_en(st, true);
+}
+
+static int adxl345_buffer_postenable(struct iio_dev *indio_dev)
+{
+ struct adxl345_state *st = iio_priv(indio_dev);
+ int ret;
+
+ ret = adxl345_set_interrupts(st);
+ if (ret < 0)
+ return ret;
+
+ st->fifo_mode = ADXL345_FIFO_STREAM;
+ return adxl345_set_fifo(st);
+}
+
+static int adxl345_buffer_predisable(struct iio_dev *indio_dev)
+{
+ struct adxl345_state *st = iio_priv(indio_dev);
+ int ret;
+
+ st->int_map = 0x00;
+
+ ret = adxl345_set_interrupts(st);
+ if (ret < 0)
+ return ret;
+
+ st->fifo_mode = ADXL345_FIFO_BYPASS;
+ return adxl345_set_fifo(st);
+}
+
+static const struct iio_buffer_setup_ops adxl345_buffer_ops = {
+ .postenable = adxl345_buffer_postenable,
+ .predisable = adxl345_buffer_predisable,
+};
+
+static int adxl345_get_status(struct adxl345_state *st)
+{
+ int ret;
+ unsigned int regval;
+
+ ret = regmap_read(st->regmap, ADXL345_REG_INT_SOURCE, &regval);
+ if (ret < 0)
+ return ret;
+
+ return (0xff & regval);
+}
+
+static int adxl345_fifo_push(struct iio_dev *indio_dev,
+ int samples)
+{
+ struct adxl345_state *st = iio_priv(indio_dev);
+ int i, ret;
+
+ if (samples <= 0)
+ return -EINVAL;
+
+ ret = adxl345_fifo_transfer(st, samples);
+ if (ret)
+ return ret;
+
+ for (i = 0; i < ADXL345_DIRS * samples; i += ADXL345_DIRS) {
+ /*
+ * To ensure that the FIFO has completely popped, there must be at least 5
+ * us between the end of reading the data registers, signified by the
+ * transition to register 0x38 from 0x37 or the CS pin going high, and the
+ * start of new reads of the FIFO or reading the FIFO_STATUS register. For
+ * SPI operation at 1.5 MHz or lower, the register addressing portion of the
+ * transmission is sufficient delay to ensure the FIFO has completely
+ * popped. It is necessary for SPI operation greater than 1.5 MHz to
+ * de-assert the CS pin to ensure a total of 5 us, which is at most 3.4 us
+ * at 5 MHz operation.
+ */
+ if (st->fifo_delay && (samples > 1))
+ udelay(3);
+
+ iio_push_to_buffers(indio_dev, &st->fifo_buf[i]);
+ }
+
+ return 0;
+}
+
+/**
+ * adxl345_event_handler() - Handle events of the ADXL345.
+ * @irq: The irq being handled.
+ * @p: The struct iio_device pointer for the device.
+ *
+ * Return: The interrupt was handled.
+ */
+static irqreturn_t adxl345_event_handler(int irq, void *p)
+{
+ struct iio_dev *indio_dev = p;
+ struct adxl345_state *st = iio_priv(indio_dev);
+ u8 int_stat;
+ int samples;
+
+ int_stat = adxl345_get_status(st);
+ if (int_stat < 0)
+ return IRQ_NONE;
+
+ if (int_stat == 0x0)
+ goto err;
+
+ if (int_stat & ADXL345_INT_OVERRUN)
+ goto err;
+
+ if (int_stat & (ADXL345_INT_DATA_READY | ADXL345_INT_WATERMARK)) {
+ samples = adxl345_get_samples(st);
+ if (samples < 0)
+ goto err;
+
+ if (adxl345_fifo_push(indio_dev, samples) < 0)
+ goto err;
+
+ }
+ return IRQ_HANDLED;
+
+err:
+ adxl345_fifo_reset(st);
+
+ return IRQ_HANDLED;
+}
+
static const struct iio_info adxl345_info = {
.attrs = &adxl345_attrs_group,
.read_raw = adxl345_read_raw,
.write_raw = adxl345_write_raw,
.write_raw_get_fmt = adxl345_write_raw_get_fmt,
+ .hwfifo_set_watermark = adxl345_set_watermark,
};

/**
@@ -222,6 +499,7 @@ int adxl345_core_probe(struct device *dev, struct regmap *regmap,
unsigned int data_format_mask = (ADXL345_DATA_FORMAT_RANGE |
ADXL345_DATA_FORMAT_FULL_RES |
ADXL345_DATA_FORMAT_SELF_TEST);
+ u8 fifo_ctl;
int ret;

indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
@@ -293,6 +571,28 @@ int adxl345_core_probe(struct device *dev, struct regmap *regmap,
if (ret < 0)
return dev_err_probe(dev, ret, "Failed to add action or reset\n");

+ if (st->irq > 0) {
+ dev_dbg(dev, "initialize for FIFO_STREAM mode\n");
+
+ ret = devm_iio_kfifo_buffer_setup(dev, indio_dev, &adxl345_buffer_ops);
+ if (ret)
+ return ret;
+
+ ret = devm_request_threaded_irq(dev, st->irq, NULL, &adxl345_event_handler,
+ IRQF_SHARED | IRQF_ONESHOT,
+ indio_dev->name, indio_dev);
+ if (ret)
+ return dev_err_probe(dev, ret, "Failed to setup triggered buffer\n");
+
+ } else {
+ dev_dbg(dev, "initialize for FIFO_BYPASS mode (fallback)\n");
+
+ fifo_ctl = ADXL345_FIFO_CTL_MODE(ADXL345_FIFO_BYPASS);
+
+ ret = regmap_write(st->regmap, ADXL345_REG_FIFO_CTL, fifo_ctl);
+ if (ret < 0)
+ return ret;
+ }
return devm_iio_device_register(dev, indio_dev);
}
EXPORT_SYMBOL_NS_GPL(adxl345_core_probe, IIO_ADXL345);
--
2.39.2