Re: [PATCH v2] iio: accel: adxl355: Add triggered buffer support

[Jonathan Cameron]

On Thu, 19 Aug 2021 23:41:33 +0530
Puranjay Mohan <puranjay12@xxxxxxxxx> wrote:

> Provide a way for continuous data capture by setting up buffer support. The
> data ready signal exposed at the DRDY pin of the ADXL355 is exploited as
> a hardware interrupt which triggers to fill the buffer.
> 
> Signed-off-by: Puranjay Mohan <puranjay12@xxxxxxxxx>

Hi Puranjay,

A fresh read and I noticed a few additional things.
All simple stuff.

I do have a slight concern that we might be setting ourselves up for problems
once the fifo is enabled.  Hopefully not, but if you have looked at that and
verified it will drop in nicely then that's great. We might be fine.

Jonathan


> ---
> Changes since v1:
> - Fix an indentation issue.
> - Add comments on layout of data in buffer.
> - Zero the buffer before using it in trigger handler.
> - Use if(ret) in place of if(ret < 0)
> ---
> drivers/iio/accel/Kconfig        |   4 +
>  drivers/iio/accel/adxl355_core.c | 162 ++++++++++++++++++++++++++++++-
>  2 files changed, 164 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/accel/Kconfig b/drivers/iio/accel/Kconfig
> index d0c45c809..9c16c1841 100644
> --- a/drivers/iio/accel/Kconfig
> +++ b/drivers/iio/accel/Kconfig
> @@ -69,6 +69,8 @@ config ADXL355_I2C
>  	depends on I2C
>  	select ADXL355
>  	select REGMAP_I2C
> +	select IIO_BUFFER
> +	select IIO_TRIGGERED_BUFFER
>  	help
>  	  Say Y here if you want to build i2c support for the Analog Devices
>  	  ADXL355 3-axis digital accelerometer.
> @@ -82,6 +84,8 @@ config ADXL355_SPI
>  	depends on SPI
>  	select ADXL355
>  	select REGMAP_SPI
> +	select IIO_BUFFER
> +	select IIO_TRIGGERED_BUFFER
>  	help
>  	  Say Y here if you want to build spi support for the Analog Devices
>  	  ADXL355 3-axis digital accelerometer.
> diff --git a/drivers/iio/accel/adxl355_core.c b/drivers/iio/accel/adxl355_core.c
> index c91d2254c..d499403dc 100644
> --- a/drivers/iio/accel/adxl355_core.c
> +++ b/drivers/iio/accel/adxl355_core.c
> @@ -9,11 +9,16 @@
>  
>  #include <linux/bits.h>
>  #include <linux/bitfield.h>
> +#include <linux/iio/buffer.h>
>  #include <linux/iio/iio.h>
> +#include <linux/iio/trigger.h>
> +#include <linux/iio/triggered_buffer.h>
> +#include <linux/iio/trigger_consumer.h>
>  #include <linux/limits.h>
>  #include <linux/math64.h>
>  #include <linux/module.h>
>  #include <linux/mod_devicetable.h>
> +#include <linux/of_irq.h>
>  #include <linux/regmap.h>
>  #include <asm/unaligned.h>
>  
> @@ -46,6 +51,7 @@
>  #define ADXL355_RANGE_REG		0x2C
>  #define ADXL355_POWER_CTL_REG		0x2D
>  #define  ADXL355_POWER_CTL_MODE_MSK	GENMASK(1, 0)
> +#define  ADXL355_POWER_CTL_DRDY_MSK	BIT(2)
>  #define ADXL355_SELF_TEST_REG		0x2E
>  #define ADXL355_RESET_REG		0x2F
>  
> @@ -165,7 +171,15 @@ struct adxl355_data {
>  	enum adxl355_hpf_3db hpf_3db;
>  	int calibbias[3];
>  	int adxl355_hpf_3db_table[7][2];
> -	u8 transf_buf[3] ____cacheline_aligned;
> +	struct iio_trigger *dready_trig;
> +	int irq;
> +	union {
> +		u8 transf_buf[3];
> +		struct {
> +			u8 buf[14];
> +			s64 ts;
> +		} buffer;
> +	} ____cacheline_aligned;
>  };
>  
>  static int adxl355_set_op_mode(struct adxl355_data *data,
> @@ -186,6 +200,23 @@ static int adxl355_set_op_mode(struct adxl355_data *data,
>  	return ret;
>  }
>  
> +static int adxl355_data_rdy_trigger_set_state(struct iio_trigger *trig,
> +					      bool state)
> +{
> +	struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
> +	struct adxl355_data *data = iio_priv(indio_dev);
> +	int ret;
> +
> +	mutex_lock(&data->lock);

Why take the lock?  What are you protecting here?

> +	ret = regmap_update_bits(data->regmap, ADXL355_POWER_CTL_REG,
> +				 ADXL355_POWER_CTL_DRDY_MSK,
> +				 FIELD_PREP(ADXL355_POWER_CTL_DRDY_MSK,
> +					    !state));
> +	mutex_unlock(&data->lock);
> +
> +	return ret;
> +}
> +
>  static void adxl355_fill_3db_frequency_table(struct adxl355_data *data)
>  {
>  	u32 multiplier;
> @@ -246,6 +277,12 @@ static int adxl355_setup(struct adxl355_data *data)
>  	if (ret)
>  		return ret;
>  
> +	ret = regmap_update_bits(data->regmap, ADXL355_POWER_CTL_REG,
> +				 ADXL355_POWER_CTL_DRDY_MSK,
> +				 FIELD_PREP(ADXL355_POWER_CTL_DRDY_MSK, 1));
> +	if (ret)
> +		return ret;
> +
>  	adxl355_fill_3db_frequency_table(data);
>  
>  	return adxl355_set_op_mode(data, ADXL355_MEASUREMENT);
> @@ -499,12 +536,74 @@ static int adxl355_read_avail(struct iio_dev *indio_dev,
>  	}
>  }
>  
> +static const unsigned long adxl355_avail_scan_masks[] = {
> +	GENMASK(3, 0),
> +	0
> +};
> +
>  static const struct iio_info adxl355_info = {
>  	.read_raw	= adxl355_read_raw,
>  	.write_raw	= adxl355_write_raw,
>  	.read_avail	= &adxl355_read_avail,
>  };
>  
> +static const struct iio_trigger_ops adxl355_trigger_ops = {
> +	.set_trigger_state = &adxl355_data_rdy_trigger_set_state,
> +	.validate_device = &iio_trigger_validate_own_device,

This is fine for now, but I'd like you to think about whether you can ultimately
drop this validation and allow other devices to be triggered from this signal.
It can be very helpful when doing sensor fusion to grab data at (approximately)
the same time from a set of different sensors.

IIRC this device has a fifo though which can complicate that option.

> +};
> +
> +static irqreturn_t adxl355_trigger_handler(int irq, void *p)
> +{
> +	struct iio_poll_func *pf = p;
> +	struct iio_dev *indio_dev = pf->indio_dev;
> +	struct adxl355_data *data = iio_priv(indio_dev);
> +	int ret;
> +
> +	mutex_lock(&data->lock);
> +
> +	/*
> +	 * data->buffer is used both for triggered buffer support
> +	 * and read/write_raw(), hence, it has to be zeroed here before usage.
> +	 */
> +	data->buffer.buf[0] = 0;
> +
> +	/*
> +	 * The accelaration data is 24 bits and big endian. It has to be saved

Spell check.  acceleration

> +	 * in 32 bits, hence, it is saved in the 2nd byte of the 4 byte buffer.
> +	 * The buf array is 14 bytes as it includes 3x4=12 bytes for
> +	 * accelaration data of x, y, and z axis. It also includes 2 bytes for
> +	 * temperature data.
> +	 */
> +	ret = regmap_bulk_read(data->regmap, ADXL355_XDATA3_REG,
> +			       &data->buffer.buf[1], 3);
> +	if (ret)
> +		goto out_unlock_notify;
> +
> +	ret = regmap_bulk_read(data->regmap, ADXL355_YDATA3_REG,
> +			       &data->buffer.buf[5], 3);
> +	if (ret)
> +		goto out_unlock_notify;
> +
> +	ret = regmap_bulk_read(data->regmap, ADXL355_ZDATA3_REG,
> +			       &data->buffer.buf[9], 3);
> +	if (ret)
> +		goto out_unlock_notify;
> +
> +	ret = regmap_bulk_read(data->regmap, ADXL355_TEMP2_REG,
> +			       &data->buffer.buf[12], 2);
> +	if (ret)
> +		goto out_unlock_notify;
> +
> +	iio_push_to_buffers_with_timestamp(indio_dev, &data->buffer,
> +					   pf->timestamp);
> +
> +out_unlock_notify:
> +	mutex_unlock(&data->lock);
> +	iio_trigger_notify_done(indio_dev->trig);
> +
> +	return IRQ_HANDLED;
> +}
> +
>  #define ADXL355_ACCEL_CHANNEL(index, reg, axis) {			\
>  	.type = IIO_ACCEL,						\
>  	.address = reg,							\
> @@ -518,6 +617,7 @@ static const struct iio_info adxl355_info = {
>  	.info_mask_shared_by_type_available =				\
>  		BIT(IIO_CHAN_INFO_SAMP_FREQ) |				\
>  		BIT(IIO_CHAN_INFO_HIGH_PASS_FILTER_3DB_FREQUENCY),	\
> +	.scan_index = index,						\
>  	.scan_type = {							\
>  		.sign = 's',						\
>  		.realbits = 20,						\
> @@ -537,6 +637,7 @@ static const struct iio_chan_spec adxl355_channels[] = {
>  		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
>  				      BIT(IIO_CHAN_INFO_SCALE) |
>  				      BIT(IIO_CHAN_INFO_OFFSET),
> +		.scan_index = 3,
>  		.scan_type = {
>  			.sign = 's',
>  			.realbits = 12,
> @@ -544,8 +645,46 @@ static const struct iio_chan_spec adxl355_channels[] = {
>  			.endianness = IIO_BE,
>  		},
>  	},
> +	IIO_CHAN_SOFT_TIMESTAMP(4),
>  };
>  
> +static int adxl355_probe_trigger(struct iio_dev *indio_dev)
> +{
> +	struct adxl355_data *data = iio_priv(indio_dev);
> +	int ret;
> +
> +	if (!data->irq) {
> +		dev_info(data->dev, "no irq, using polling\n");

I would move this check externally so that we never probe if it's
not wired up.  It's also easy to tell (no trigger available) so
the dev_info is probably unnecessary noise in the log.


> +		return 0;
> +	}
> +
> +	data->dready_trig = devm_iio_trigger_alloc(data->dev, "%s-dev%d",
> +						   indio_dev->name,
> +						   indio_dev->id);
> +	if (!data->dready_trig)
> +		return -ENOMEM;
> +
> +	data->dready_trig->ops = &adxl355_trigger_ops;
> +	iio_trigger_set_drvdata(data->dready_trig, indio_dev);
> +
> +	ret = devm_request_irq(data->dev, data->irq,
> +			       &iio_trigger_generic_data_rdy_poll,
> +			       IRQF_ONESHOT, "adxl355_irq", data->dready_trig);
> +	if (ret)
> +		return dev_err_probe(data->dev, ret, "request irq %d failed\n",
> +				     data->irq);
> +
> +	ret = devm_iio_trigger_register(data->dev, data->dready_trig);
> +	if (ret) {
> +		dev_err(data->dev, "iio trigger register failed\n");
> +		return ret;
> +	}
> +
> +	indio_dev->trig = iio_trigger_get(data->dready_trig);
> +
> +	return 0;
> +}
> +
>  int adxl355_core_probe(struct device *dev, struct regmap *regmap,
>  		       const char *name)
>  {
> @@ -563,18 +702,37 @@ int adxl355_core_probe(struct device *dev, struct regmap *regmap,
>  	data->op_mode = ADXL355_STANDBY;
>  	mutex_init(&data->lock);
>  
> +	/*
> +	 * TODO: Would be good to move it to the generic version.
> +	 */
> +	ret = of_irq_get_byname(dev->of_node, "DRDY");
> +	if (ret > 0)
> +		data->irq = ret;

If you do this get down near the probe_trigger() call then you should be able to
avoid keeping a copy of irq in data.  Just pass it into that function as
a parameter.

> +
>  	indio_dev->name = name;
>  	indio_dev->info = &adxl355_info;
>  	indio_dev->modes = INDIO_DIRECT_MODE;
>  	indio_dev->channels = adxl355_channels;
>  	indio_dev->num_channels = ARRAY_SIZE(adxl355_channels);
> +	indio_dev->available_scan_masks = adxl355_avail_scan_masks;
>  
>  	ret = adxl355_setup(data);
> -	if (ret < 0) {
> +	if (ret) {

This looks to be an unrelated cleanup.  Please move to a precursor patch as
it adds noise in this one which is fiddly enough without it ;)

>  		dev_err(dev, "ADXL355 setup failed\n");
>  		return ret;
>  	}
>  
> +	ret = devm_iio_triggered_buffer_setup(dev, indio_dev,
> +					      &iio_pollfunc_store_time,
> +					      &adxl355_trigger_handler, NULL);
> +	if (ret)
> +		return dev_err_probe(dev, ret,
> +				     "iio triggered buffer setup failed\n");
> +
> +	ret = adxl355_probe_trigger(indio_dev);
> +	if (ret)
> +		return ret;
> +
>  	return devm_iio_device_register(dev, indio_dev);
>  }
>  EXPORT_SYMBOL_GPL(adxl355_core_probe);