Date:   Sun, 19 Aug 2018 18:25:41 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Stefan Popa <stefan.popa@...log.com>
Cc:     <broonie@...nel.org>, <lars@...afoo.de>,
        <Michael.Hennerich@...log.com>, <knaack.h@....de>,
        <pmeerw@...erw.net>, <mark.rutland@....com>, <davem@...emloft.net>,
        <mchehab+samsung@...nel.org>, <gregkh@...uxfoundation.org>,
        <akpm@...ux-foundation.org>, <robh+dt@...nel.org>,
        <linux-iio@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 4/6] iio:adxl372: Add FIFO and interrupts support

On Fri, 10 Aug 2018 11:46:21 +0300
Stefan Popa <stefan.popa@...log.com> wrote:

> This patch adds support for the adxl372 FIFO. In order to accomplish this,
> triggered buffers were used.
> 
> The number of FIFO samples which trigger the watermark interrupt can be
> configured by using the buffer watermark. The FIFO format is determined by
> configuring the scan elements for each axis. The FIFO data is pushed to the
> IIO device's buffer.
> 
> Signed-off-by: Stefan Popa <stefan.popa@...log.com>

Hi Stefan,  I'm afraid I missed a few things on previous versions of this.

If we are going to expose a general purpose trigger or allow a driver
to use a general purpose trigger (this currently does both as neither validate
function is provided to limit it's usage), then the trigger 'must' correspond
to one interrupt per reading.  It's absolutely fine to have a device specific
trigger where that isn't true though normally we would only bother exposing it
as a trigger if there as an alternative.

A classic case would be that we have a fifo and use it if the trigger is the
devices only trigger, but in the event of a different trigger being selected
we are happy to use it with the fifo length set to 1 (or it just turned off).

That allows the use of say a sysfs of hrtimer trigger with us getting the expected
1 sample set per trigger, and the use of the fifo for this device alone.
To do that you have make sure you have a validate_device callback provided
for the trigger so it rejects other devices.

We can just forgo alternative triggers and have the buffer driven directly.
I don't really like that option though as it leads to abi changes if we ever
want to add alternatives in future though we can sort of get around that using
default triggers.

So the simple solution for now is to provide validate_trigger and validate_device
callbacks to fix it to use them only when they are the same device.

We can do clever stuff later if needed to enable other triggers.

Jonathan

> ---
>  drivers/iio/accel/adxl372.c | 357 +++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 356 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/accel/adxl372.c b/drivers/iio/accel/adxl372.c
> index db9ecd2..1e2519a 100644
> --- a/drivers/iio/accel/adxl372.c
> +++ b/drivers/iio/accel/adxl372.c
> @@ -6,12 +6,19 @@
>   */
>  
>  #include <linux/bitops.h>
> +#include <linux/interrupt.h>
> +#include <linux/irq.h>
>  #include <linux/module.h>
>  #include <linux/regmap.h>
>  #include <linux/spi/spi.h>
>  
>  #include <linux/iio/iio.h>
>  #include <linux/iio/sysfs.h>
> +#include <linux/iio/buffer.h>
> +#include <linux/iio/events.h>

Why events?

> +#include <linux/iio/trigger.h>
> +#include <linux/iio/trigger_consumer.h>
> +#include <linux/iio/triggered_buffer.h>
>  
>  /* ADXL372 registers definition */
>  #define ADXL372_DEVID			0x00
> @@ -123,6 +130,9 @@
>  #define ADXL372_INT1_MAP_LOW_MSK		BIT(7)
>  #define ADXL372_INT1_MAP_LOW_MODE(x)		(((x) & 0x1) << 7)
>  
> +/* The ADXL372 includes a deep, 512 sample FIFO buffer */
> +#define ADXL372_FIFO_SIZE			512
> +
>  /*
>   * At +/- 200g with 12-bit resolution, scale is computed as:
>   * (200 + 200) * 9.81 / (2^12 - 1) = 0.958241
> @@ -170,6 +180,43 @@ static const unsigned int adxl372_th_reg_high_addr[3] = {
>  	[ADXL372_INACTIVITY] = ADXL372_X_THRESH_INACT_H,
>  };
>  
> +enum adxl372_fifo_format {
> +	ADXL372_XYZ_FIFO,
> +	ADXL372_X_FIFO,
> +	ADXL372_Y_FIFO,
> +	ADXL372_XY_FIFO,
> +	ADXL372_Z_FIFO,
> +	ADXL372_XZ_FIFO,
> +	ADXL372_YZ_FIFO,
> +	ADXL372_XYZ_PEAK_FIFO,
> +};
> +
> +enum adxl372_fifo_mode {
> +	ADXL372_FIFO_BYPASSED,
> +	ADXL372_FIFO_STREAMED,
> +	ADXL372_FIFO_TRIGGERED,
> +	ADXL372_FIFO_OLD_SAVED
> +};
> +
> +static const int adxl372_samp_freq_tbl[5] = {
> +	400, 800, 1600, 3200, 6400,
> +};
> +
> +struct adxl372_axis_lookup {
> +	unsigned int bits;
> +	enum adxl372_fifo_format fifo_format;
> +};
> +
> +static const struct adxl372_axis_lookup adxl372_axis_lookup_table[] = {
> +	{ BIT(0), ADXL372_X_FIFO },
> +	{ BIT(1), ADXL372_Y_FIFO },
> +	{ BIT(2), ADXL372_Z_FIFO },
> +	{ BIT(0) | BIT(1), ADXL372_XY_FIFO },
> +	{ BIT(0) | BIT(2), ADXL372_XZ_FIFO },
> +	{ BIT(1) | BIT(2), ADXL372_YZ_FIFO },
> +	{ BIT(0) | BIT(1) | BIT(2), ADXL372_XYZ_FIFO },
> +};
> +
>  #define ADXL372_ACCEL_CHANNEL(index, reg, axis) {			\
>  	.type = IIO_ACCEL,						\
>  	.address = reg,							\
> @@ -177,6 +224,13 @@ static const unsigned int adxl372_th_reg_high_addr[3] = {
>  	.channel2 = IIO_MOD_##axis,					\
>  	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),			\
>  	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),		\
> +	.scan_index = index,						\
> +	.scan_type = {							\
> +		.sign = 's',						\
> +		.realbits = 12,						\
> +		.storagebits = 16,					\
> +		.shift = 4,						\
> +	},								\
>  }
>  
>  static const struct iio_chan_spec adxl372_channels[] = {
> @@ -188,12 +242,29 @@ static const struct iio_chan_spec adxl372_channels[] = {
>  struct adxl372_state {
>  	struct spi_device		*spi;
>  	struct regmap			*regmap;
> +	struct iio_trigger		*dready_trig;
> +	enum adxl372_fifo_mode		fifo_mode;
> +	enum adxl372_fifo_format	fifo_format;
>  	enum adxl372_op_mode		op_mode;
>  	enum adxl372_act_proc_mode	act_proc_mode;
>  	enum adxl372_odr		odr;
>  	enum adxl372_bandwidth		bw;
>  	u32				act_time_ms;
>  	u32				inact_time_ms;
> +	u8				fifo_set_size;
> +	u8				int1_bitmask;
> +	u8				int2_bitmask;
> +	u16				watermark;
> +	__be16				fifo_buf[ADXL372_FIFO_SIZE];
> +};
> +
> +static const unsigned long adxl372_channel_masks[] = {
> +	BIT(0), BIT(1), BIT(2),
> +	BIT(0) | BIT(1),
> +	BIT(0) | BIT(2),
> +	BIT(1) | BIT(2),
> +	BIT(0) | BIT(1) | BIT(2),
> +	0
>  };
>  
>  static int adxl372_read_axis(struct adxl372_state *st, u8 addr)
> @@ -359,6 +430,112 @@ static int adxl372_set_inactivity_time_ms(struct adxl372_state *st,
>  	return ret;
>  }
>  
> +static int adxl372_set_interrupts(struct adxl372_state *st,
> +				  unsigned char int1_bitmask,
> +				  unsigned char int2_bitmask)
> +{
> +	int ret;
> +
> +	ret = regmap_write(st->regmap, ADXL372_INT1_MAP, int1_bitmask);
> +	if (ret < 0)
> +		return ret;
> +
> +	return regmap_write(st->regmap, ADXL372_INT2_MAP, int2_bitmask);
> +}
> +
> +static int adxl372_configure_fifo(struct adxl372_state *st)
> +{
> +	unsigned int fifo_samples, fifo_ctl;
> +	int ret;
> +
> +	/* FIFO must be configured while in standby mode */
> +	ret = adxl372_set_op_mode(st, ADXL372_STANDBY);
> +	if (ret < 0)
> +		return ret;
> +
> +	fifo_samples = st->watermark & 0xFF;
> +	fifo_ctl = ADXL372_FIFO_CTL_FORMAT_MODE(st->fifo_format) |
> +		   ADXL372_FIFO_CTL_MODE_MODE(st->fifo_mode) |
> +		   ADXL372_FIFO_CTL_SAMPLES_MODE(st->watermark);
> +
> +	ret = regmap_write(st->regmap, ADXL372_FIFO_SAMPLES, fifo_samples);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = regmap_write(st->regmap, ADXL372_FIFO_CTL, fifo_ctl);
> +	if (ret < 0)
> +		return ret;
> +
> +	return adxl372_set_op_mode(st, ADXL372_FULL_BW_MEASUREMENT);
> +}
> +
> +static int adxl372_get_status(struct adxl372_state *st,
> +			      u8 *status1, u8 *status2,
> +			      u16 *fifo_entries)
> +{
> +	__be32 buf;
> +	u32 val;
> +	int ret;
> +
> +	/* STATUS1, STATUS2, FIFO_ENTRIES2 and FIFO_ENTRIES are adjacent regs */
> +	ret = regmap_bulk_read(st->regmap, ADXL372_STATUS_1,
> +			       &buf, sizeof(buf));
> +	if (ret < 0)
> +		return ret;
> +
> +	val = be32_to_cpu(buf);
> +
> +	*status1 = (val >> 24) & 0x0F;
> +	*status2 = (val >> 16) & 0x0F;
> +	/*
> +	 * FIFO_ENTRIES contains the least significant byte, and FIFO_ENTRIES2
> +	 * contains the two most significant bits
> +	 */
> +	*fifo_entries = val & 0x3FF;
> +
> +	return ret;
> +}
> +
> +static irqreturn_t adxl372_trigger_handler(int irq, void  *p)
> +{
> +	struct iio_poll_func *pf = p;
> +	struct iio_dev *indio_dev = pf->indio_dev;
> +	struct adxl372_state *st = iio_priv(indio_dev);
> +	u8 status1, status2;
> +	u16 fifo_entries;
> +	int i, ret;
> +
> +	ret = adxl372_get_status(st, &status1, &status2, &fifo_entries);
> +	if (ret < 0)
> +		goto err;
> +
> +	if (st->fifo_mode != ADXL372_FIFO_BYPASSED &&
> +	    ADXL372_STATUS_1_FIFO_FULL(status1)) {
> +		/*
> +		 * When reading data from multiple axes from the FIFO,
> +		 * to ensure that data is not overwritten and stored out
> +		 * of order at least one sample set must be left in the
> +		 * FIFO after every read.
> +		 */
> +		fifo_entries -= st->fifo_set_size;
> +
> +		/* Read data from the FIFO */
> +		ret = regmap_noinc_read(st->regmap, ADXL372_FIFO_DATA,
> +					st->fifo_buf,
> +					fifo_entries * sizeof(u16));
> +		if (ret < 0)
> +			goto err;
> +
> +		/* Each sample is 2 bytes */
> +		for (i = 0; i < fifo_entries * sizeof(u16);
> +		     i += st->fifo_set_size * sizeof(u16))
> +			iio_push_to_buffers(indio_dev, &st->fifo_buf[i]);
> +	}
> +err:
> +	iio_trigger_notify_done(indio_dev->trig);
> +	return IRQ_HANDLED;
> +}
> +
>  static int adxl372_setup(struct adxl372_state *st)
>  {
>  	unsigned int regval;
> @@ -438,7 +615,12 @@ static int adxl372_read_raw(struct iio_dev *indio_dev,
>  
>  	switch (info) {
>  	case IIO_CHAN_INFO_RAW:
> +		ret = iio_device_claim_direct_mode(indio_dev);
> +		if (ret)
> +			return ret;
> +
>  		ret = adxl372_read_axis(st, chan->address);
> +		iio_device_release_direct_mode(indio_dev);
>  		if (ret < 0)
>  			return ret;
>  
> @@ -454,16 +636,153 @@ static int adxl372_read_raw(struct iio_dev *indio_dev,
>  	}
>  }
>  
> +static ssize_t adxl372_get_fifo_enabled(struct device *dev,
> +					  struct device_attribute *attr,
> +					  char *buf)
> +{
> +	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> +	struct adxl372_state *st = iio_priv(indio_dev);
> +
> +	return sprintf(buf, "%d\n", st->fifo_mode);
> +}
> +
> +static ssize_t adxl372_get_fifo_watermark(struct device *dev,
> +					  struct device_attribute *attr,
> +					  char *buf)
> +{
> +	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> +	struct adxl372_state *st = iio_priv(indio_dev);
> +
> +	return sprintf(buf, "%d\n", st->watermark);
> +}
> +
> +static IIO_CONST_ATTR(hwfifo_watermark_min, "1");
> +static IIO_CONST_ATTR(hwfifo_watermark_max,
> +		      __stringify(ADXL372_FIFO_SIZE));
> +static IIO_DEVICE_ATTR(hwfifo_watermark, 0444,
> +		       adxl372_get_fifo_watermark, NULL, 0);
> +static IIO_DEVICE_ATTR(hwfifo_enabled, 0444,
> +		       adxl372_get_fifo_enabled, NULL, 0);
> +
> +static const struct attribute *adxl372_fifo_attributes[] = {
> +	&iio_const_attr_hwfifo_watermark_min.dev_attr.attr,
> +	&iio_const_attr_hwfifo_watermark_max.dev_attr.attr,
> +	&iio_dev_attr_hwfifo_watermark.dev_attr.attr,
> +	&iio_dev_attr_hwfifo_enabled.dev_attr.attr,
> +	NULL,
> +};
> +
> +static int adxl372_set_watermark(struct iio_dev *indio_dev, unsigned int val)
> +{
> +	struct adxl372_state *st  = iio_priv(indio_dev);
> +
> +	if (val > ADXL372_FIFO_SIZE)
> +		val = ADXL372_FIFO_SIZE;
> +
> +	st->watermark = val;
> +
> +	return 0;
> +}
> +
> +static int adxl372_buffer_postenable(struct iio_dev *indio_dev)
> +{
> +	struct adxl372_state *st = iio_priv(indio_dev);
> +	unsigned int mask;
> +	int i, ret;
> +
> +	ret = adxl372_set_interrupts(st, ADXL372_INT1_MAP_FIFO_FULL_MSK, 0);
> +	if (ret < 0)
> +		return ret;
> +
> +	mask = *indio_dev->active_scan_mask;
> +
> +	for (i = 0; i < ARRAY_SIZE(adxl372_axis_lookup_table); i++) {
> +		if (mask == adxl372_axis_lookup_table[i].bits)
> +			break;
> +	}
> +
> +	if (i == ARRAY_SIZE(adxl372_axis_lookup_table))
> +		return -EINVAL;
> +
> +	st->fifo_format = adxl372_axis_lookup_table[i].fifo_format;
> +	st->fifo_set_size = bitmap_weight(indio_dev->active_scan_mask,
> +					  indio_dev->masklength);
> +	/*
> +	 * The 512 FIFO samples can be allotted in several ways, such as:
> +	 * 170 sample sets of concurrent 3-axis data
> +	 * 256 sample sets of concurrent 2-axis data (user selectable)
> +	 * 512 sample sets of single-axis data
> +	 */
> +	if ((st->watermark * st->fifo_set_size) > ADXL372_FIFO_SIZE)
> +		st->watermark = (ADXL372_FIFO_SIZE  / st->fifo_set_size);
> +
> +	st->fifo_mode = ADXL372_FIFO_STREAMED;
> +
> +	ret = adxl372_configure_fifo(st);
> +	if (ret < 0) {
> +		st->fifo_mode = ADXL372_FIFO_BYPASSED;
> +		adxl372_set_interrupts(st, 0, 0);
> +		return ret;
> +	}
> +
> +	return iio_triggered_buffer_postenable(indio_dev);
> +}
> +
> +static int adxl372_buffer_predisable(struct iio_dev *indio_dev)
> +{
> +	struct adxl372_state *st = iio_priv(indio_dev);
> +	int ret;
> +
> +	ret = iio_triggered_buffer_predisable(indio_dev);
> +	if (ret < 0)
> +		return ret;
> +
> +	adxl372_set_interrupts(st, 0, 0);
> +	st->fifo_mode = ADXL372_FIFO_BYPASSED;
> +	adxl372_configure_fifo(st);
> +
> +	return 0;
> +}
> +
> +static const struct iio_buffer_setup_ops adxl372_buffer_ops = {
> +	.postenable = adxl372_buffer_postenable,
> +	.predisable = adxl372_buffer_predisable,
> +};
> +
> +static int adxl372_dready_trig_set_state(struct iio_trigger *trig,
> +					 bool state)
> +{
> +	struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
> +	struct adxl372_state *st = iio_priv(indio_dev);
> +	unsigned long int mask = 0;
> +
> +	if (state)
> +		mask = ADXL372_INT1_MAP_FIFO_FULL_MSK;
> +
> +	return adxl372_set_interrupts(st, mask, 0);
> +}
> +
> +static const struct iio_trigger_ops adxl372_trigger_ops = {
> +	.set_trigger_state = adxl372_dready_trig_set_state,
> +};
> +
>  static const struct iio_info adxl372_info = {
>  	.read_raw = adxl372_read_raw,
>  	.debugfs_reg_access = &adxl372_reg_access,
> +	.hwfifo_set_watermark = adxl372_set_watermark,
>  };
>  
> +static bool adxl372_readable_noinc_reg(struct device *dev, unsigned int reg)
> +{
> +	return (reg == ADXL372_FIFO_DATA);
> +}
> +
>  static const struct regmap_config adxl372_spi_regmap_config = {
>  	.reg_bits = 7,
>  	.pad_bits = 1,
>  	.val_bits = 8,
>  	.read_flag_mask = BIT(0),
> +	.readable_noinc_reg = adxl372_readable_noinc_reg,
>  };
>  
>  static int adxl372_probe(struct spi_device *spi)
> @@ -490,10 +809,11 @@ static int adxl372_probe(struct spi_device *spi)
>  
>  	indio_dev->channels = adxl372_channels;
>  	indio_dev->num_channels = ARRAY_SIZE(adxl372_channels);
> +	indio_dev->available_scan_masks = adxl372_channel_masks;
>  	indio_dev->dev.parent = &spi->dev;
>  	indio_dev->name = spi_get_device_id(spi)->name;
>  	indio_dev->info = &adxl372_info;
> -	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->modes = INDIO_DIRECT_MODE | INDIO_BUFFER_SOFTWARE;
>  
>  	ret = adxl372_setup(st);
>  	if (ret < 0) {
> @@ -501,6 +821,41 @@ static int adxl372_probe(struct spi_device *spi)
>  		return ret;
>  	}
>  
> +	ret = devm_iio_triggered_buffer_setup(&st->spi->dev,
> +					      indio_dev, NULL,
> +					      adxl372_trigger_handler,
> +					      &adxl372_buffer_ops);
> +	if (ret < 0)
> +		return ret;
> +
> +	iio_buffer_set_attrs(indio_dev->buffer, adxl372_fifo_attributes);
> +
> +	if (st->spi->irq) {
> +		st->dready_trig = devm_iio_trigger_alloc(&st->spi->dev,
> +							 "%s-dev%d",
> +							 indio_dev->name,
> +							 indio_dev->id);
> +		if (st->dready_trig == NULL)
> +			return -ENOMEM;
> +
> +		st->dready_trig->ops = &adxl372_trigger_ops;
> +		st->dready_trig->dev.parent = &st->spi->dev;
> +		iio_trigger_set_drvdata(st->dready_trig, indio_dev);
> +		ret = devm_iio_trigger_register(&st->spi->dev, st->dready_trig);
> +		if (ret < 0)
> +			return ret;
> +
> +		indio_dev->trig = iio_trigger_get(st->dready_trig);
> +
> +		ret = devm_request_threaded_irq(&st->spi->dev, st->spi->irq,
> +					iio_trigger_generic_data_rdy_poll,
> +					NULL,
> +					IRQF_TRIGGER_RISING | IRQF_ONESHOT,
> +					indio_dev->name, st->dready_trig);
> +		if (ret < 0)
> +			return ret;
> +	}
> +
>  	return devm_iio_device_register(&st->spi->dev, indio_dev);
>  }
>  

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