Re: [PATCH v8 6/7] iio: accel: adxl345: add FIFO with watermark events

Jonathan Cameron
2024-12-28T14:45:46Z

On Wed, 25 Dec 2024 18:13:37 +0000
Lothar Rubusch <l.rubusch@gmail.com> wrote:

> 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.h | 27 ++-
> drivers/iio/accel/adxl345_core.c | 305 ++++++++++++++++++++++++++++++-
> 2 files changed, 321 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/iio/accel/adxl345.h b/drivers/iio/accel/adxl345.h
> index 6f39f16d3..bf9e86cff 100644
> --- a/drivers/iio/accel/adxl345.h
> +++ b/drivers/iio/accel/adxl345.h
> @@ -15,18 +15,32 @@
> #define ADXL345_REG_OFS_AXIS(index) (ADXL345_REG_OFSX + (index))
> #define ADXL345_REG_BW_RATE 0x2C
> #define ADXL345_REG_POWER_CTL 0x2D
> +#define ADXL345_REG_INT_ENABLE 0x2E
> +#define ADXL345_REG_INT_MAP 0x2F
> +#define ADXL345_REG_INT_SOURCE 0x30
> +#define ADXL345_REG_INT_SOURCE_MSK 0xFF
> #define ADXL345_REG_DATA_FORMAT 0x31
> -#define ADXL345_REG_DATAX0 0x32
> -#define ADXL345_REG_DATAY0 0x34
> -#define ADXL345_REG_DATAZ0 0x36
> -#define ADXL345_REG_DATA_AXIS(index) \
> - (ADXL345_REG_DATAX0 + (index) * sizeof(__le16))
> +#define ADXL345_REG_XYZ_BASE 0x32
> +#define ADXL345_REG_DATA_AXIS(index) \
> + (ADXL345_REG_XYZ_BASE + (index) * sizeof(__le16))
>
> +#define ADXL345_REG_FIFO_CTL 0x38
> +#define ADXL345_REG_FIFO_STATUS 0x39
> +#define ADXL345_REG_FIFO_STATUS_MSK 0x3F
> +
> +#define ADXL345_FIFO_CTL_SAMPLES(x) FIELD_PREP(GENMASK(4, 0), x)
These need linux/bitfield.h to be included.

However, that got me looking closer at this and it should be done
differently.

Just define the masks in here and put the FIELD_PREP() inline in the
c file. Same for the various other FIELD_PREP macros in here.

It may seem convenient to wrap all this up here, but in general
I'd rather see that these are simple FIELD_PREP() calls where they
are used inline.

Thanks,

Jonathan

> +/* 0: INT1, 1: INT2 */
> +#define ADXL345_FIFO_CTL_TRIGGER(x) FIELD_PREP(BIT(5), x)
> +#define ADXL345_FIFO_CTL_MODE(x) FIELD_PREP(GENMASK(7, 6), x)
> +
> +#define ADXL345_INT_DATA_READY BIT(7)
> +#define ADXL345_INT_WATERMARK BIT(1)
> +#define ADXL345_INT_OVERRUN BIT(0)
> #define ADXL345_BW_RATE GENMASK(3, 0)
> #define ADXL345_BASE_RATE_NANO_HZ 97656250LL
>
> -#define ADXL345_POWER_CTL_MEASURE BIT(3)
> #define ADXL345_POWER_CTL_STANDBY 0x00
> +#define ADXL345_POWER_CTL_MEASURE BIT(3)
>
> #define ADXL345_DATA_FORMAT_RANGE GENMASK(1, 0) /* Set the g range */
> #define ADXL345_DATA_FORMAT_JUSTIFY BIT(2) /* Left-justified (MSB) mode */
> @@ -40,6 +54,7 @@
> #define ADXL345_DATA_FORMAT_16G 3
>
> #define ADXL345_DEVID 0xE5
> +#define ADXL345_FIFO_SIZE 32
>
> /*
> * In full-resolution mode, scale factor is maintained at ~4 mg/LSB
> diff --git a/drivers/iio/accel/adxl345_core.c b/drivers/iio/accel/adxl345_core.c
> index 987a0fe03..738960298 100644
> --- a/drivers/iio/accel/adxl345_core.c
> +++ b/drivers/iio/accel/adxl345_core.c
> @@ -15,9 +15,17 @@
>
> #include <linux/iio/iio.h>
> #include <linux/iio/sysfs.h>
> +#include <linux/iio/buffer.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
> +
> #define ADXL345_INT_NONE 0xff
> #define ADXL345_INT1 0
> #define ADXL345_INT2 1
> @@ -28,25 +36,66 @@ struct adxl345_state {
> bool fifo_delay; /* delay: delay is needed for SPI */
> int irq;
> u8 intio;
> + u8 int_map;
> + u8 watermark;
> + u8 fifo_mode;
> + __le16 fifo_buf[ADXL345_DIRS * ADXL345_FIFO_SIZE + 1] __aligned(IIO_DMA_MINALIGN);
> };
>
> -#define ADXL345_CHANNEL(index, axis) { \
> +#define ADXL345_CHANNEL(index, reg, axis) { \
> .type = IIO_ACCEL, \
> .modified = 1, \
> .channel2 = IIO_MOD_##axis, \
> - .address = index, \
> + .address = (reg), \
> .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | \
> BIT(IIO_CHAN_INFO_CALIBBIAS), \
> .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, \
> + .endianness = IIO_LE, \
> + }, \
> }
>
> +enum adxl345_chans {
> + chan_x, chan_y, chan_z,
> +};
> +
> static const struct iio_chan_spec adxl345_channels[] = {
> - ADXL345_CHANNEL(0, X),
> - ADXL345_CHANNEL(1, Y),
> - ADXL345_CHANNEL(2, Z),
> + ADXL345_CHANNEL(0, chan_x, X),
> + ADXL345_CHANNEL(1, chan_y, Y),
> + ADXL345_CHANNEL(2, chan_z, Z),
> };
>
> +static const unsigned long adxl345_scan_masks[] = {
> + BIT(chan_x) | BIT(chan_y) | BIT(chan_z),
> + 0
> +};
> +
> +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 = FIELD_GET(ADXL345_REG_INT_SOURCE_MSK,
> + 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)
> @@ -132,6 +181,24 @@ 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;
> +
> + value = min(value, ADXL345_FIFO_SIZE - 1);
> +
> + 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)
> @@ -186,11 +253,217 @@ static const struct attribute_group adxl345_attrs_group = {
> .attrs = adxl345_attrs,
> };
>
> +static int adxl345_set_fifo(struct adxl345_state *st)
> +{
> + int ret;
> +
> + /* FIFO should only be configured while in standby mode */
> + ret = adxl345_set_measure_en(st, false);
> + if (ret < 0)
> + return ret;
> +
> + ret = regmap_write(st->regmap, ADXL345_REG_FIFO_CTL,
> + ADXL345_FIFO_CTL_SAMPLES(st->watermark) |
> + ADXL345_FIFO_CTL_TRIGGER(st->intio) |
> + ADXL345_FIFO_CTL_MODE(st->fifo_mode));
> + 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 FIELD_GET(ADXL345_REG_FIFO_STATUS_MSK, 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.
> + *
> + * 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, i.e. 6 bytes at once.
> + *
> + * Return: 0 or error value.
> + */
> +static int adxl345_fifo_transfer(struct adxl345_state *st, int samples)
> +{
> + size_t count;
> + int i, ret = 0;
> +
> + /* count is the 3x the fifo_buf element size, hence 6B */
> + count = sizeof(st->fifo_buf[0]) * ADXL345_DIRS;
> + for (i = 0; i < samples; i++) {
> + /* read 3x 2 byte elements from base address into next fifo_buf position */
> + ret = regmap_bulk_read(st->regmap, ADXL345_REG_XYZ_BASE,
> + st->fifo_buf + (i * count / 2), count);
> + if (ret < 0)
> + return ret;
> +
> + /*
> + * 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);
> + }
> + 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->fifo_mode = ADXL345_FIFO_BYPASS;
> + ret = adxl345_set_fifo(st);
> + if (ret < 0)
> + return ret;
> +
> + st->int_map = 0x00;
> + return adxl345_set_interrupts(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 FIELD_GET(ADXL345_REG_INT_SOURCE_MSK, 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)
> + iio_push_to_buffers(indio_dev, &st->fifo_buf[i]);
> +
> + return 0;
> +}
> +
> +/**
> + * adxl345_irq_handler() - Handle irqs 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_irq_handler(int irq, void *p)
> +{
> + struct iio_dev *indio_dev = p;
> + struct adxl345_state *st = iio_priv(indio_dev);
> + int int_stat;
> + int samples;
> +
> + int_stat = adxl345_get_status(st);
> + if (int_stat <= 0)
> + return IRQ_NONE;
> +
> + if (int_stat & ADXL345_INT_OVERRUN)
> + goto err;
> +
> + if (int_stat & 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,
> };
>
> /**
> @@ -221,6 +494,7 @@ int adxl345_core_probe(struct device *dev, struct regmap *regmap,
> ADXL345_DATA_FORMAT_JUSTIFY |
> ADXL345_DATA_FORMAT_FULL_RES |
> ADXL345_DATA_FORMAT_SELF_TEST);
> + u8 fifo_ctl;
> int ret;
>
> indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
> @@ -239,6 +513,7 @@ int adxl345_core_probe(struct device *dev, struct regmap *regmap,
> indio_dev->modes = INDIO_DIRECT_MODE;
> indio_dev->channels = adxl345_channels;
> indio_dev->num_channels = ARRAY_SIZE(adxl345_channels);
> + indio_dev->available_scan_masks = adxl345_scan_masks;
>
> if (setup) {
> /* Perform optional initial bus specific configuration */
> @@ -289,6 +564,26 @@ int adxl345_core_probe(struct device *dev, struct regmap *regmap,
> st->intio = ADXL345_INT_NONE;
> }
>
> + if (st->intio != ADXL345_INT_NONE) {
> + /* FIFO_STREAM mode is going to be activated later */
> + 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_irq_handler,
> + IRQF_SHARED | IRQF_ONESHOT,
> + indio_dev->name, indio_dev);
> + if (ret)
> + return ret;
> + } else {
> + /* FIFO_BYPASS mode */
> + 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);