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

Lothar Rubusch
2024-12-28T16:12:35Z

On Sat, Dec 28, 2024 at 3:45 PM Jonathan Cameron <jic23@kernel.org> wrote:
>
> 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.
>

Sure, I can do this.

> 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.
>

Ok, I understand, the masks stay in the adxl345.h and the FIELD_RPEP()
macros better go to where they are used, i.e. the adxl345_core.c.

Thank you for reviewing this. I was a bit unsure about using the
FIELD_PREP() / GENMASK() combinations correctly. The code seems to
work for me, though. For future usage of those macros: Generally my
usage of those macros is correct?

Do I understand correctly, on the long run it would generally be
cleaner, also to migrate the defines to the adxl345_core.c? IMHO,
probably most of the constants in the adxl345.h can be private to
adxl345_core.c, and probably better should.

Best regards,
L

> 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);
>