Merge tag 'staging-4.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging

Pull staging and IIO updates from Greg KH:
 "Here is the big staging and IIO driver pull request for 4.9-rc1.

  There are a lot of patches in here, the majority due to the
  drivers/staging/greybus/ subsystem being merged in with full
  development history that went back a few years, in order to preserve
  the work that those developers did over time.

  Lots and lots of tiny cleanups happened in the tree as well, due to
  the Outreachy application process and lots of other developers showing
  up for the first time to clean code up.  Along with those changes, we
  deleted a wireless driver, and added a raspberrypi driver (currently
  marked broken), and lots of new iio drivers.

  Overall the tree still shrunk with more lines removed than added,
  about 10 thousand lines removed in total. Full details are in the very
  long shortlog below.

  All of this has been in the linux-next tree with no issues. There will
  be some merge problems with other subsystem trees, but those are all
  minor problems and shouldn't be hard to work out when they happen
  (MAINTAINERS and some lustre build problems with the IB tree)"

And furter from me asking for clarification about greybus:
 "Right now there is a phone from Motorola shipping with this code (a
  slightly older version, but the same tree), so even though Ara is not
  alive in the same form, the functionality is happening. We are working
  with the developers of that phone to merge the newer stuff in with
  their fork so they can use the upstream version in future versions of
  their phone product line.

  Toshiba has at least one chip shipping in their catalog that
  needs/uses this protocol over a Unipro link, and rumor has it that
  there might be more in the future.

  There are also other users of the greybus protocols, there is a talk
  next week at ELC that shows how it is being used across a network
  connection to control a device, and previous ELC talks have showed the
  protocol stack being used over USB to drive embedded Linux boards.
  I've also talked to some people who are starting to work to add a host
  controller driver to control arduinos as the greybus PHY protocols are
  very useful to control a serial/i2c/spio/whatever device across a
  random physical link, as it is a way to have a self-describing device
  be attached to a host without needing manual configuration.

  So yes, people are using it, and there is still the chance that it
  will show up in a phone/laptop/tablet/whatever from Google in the
  future as well, the tech isn't dead, even if the original large phone
  project happens to be"

* tag 'staging-4.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging: (3703 commits)
  Staging: fbtft: Fix bug in fbtft-core
  staging: rtl8188eu: fix double unlock error in rtw_resume_process()
  staging:r8188eu: remove GEN_MLME_EXT_HANDLER macro
  staging:r8188eu: remove GEN_DRV_CMD_HANDLER macro
  staging:r8188eu: remove GEN_EVT_CODE macro
  staging:r8188eu: remove GEN_CMD_CODE macro
  staging:r8188eu: remove pkt_newalloc member of the recv_buf structure
  staging:r8188eu: remove rtw_handle_dualmac declaration
  staging:r8188eu: remove (RGTRY|BSSID)_(OFT|SZ) macros
  staging:r8188eu: change rtl8188e_process_phy_info function argument type
  Staging: fsl-mc: Remove blank lines
  Staging: fsl-mc: Fix unaligned * in block comments
  Staging: comedi: Align the * in block comments
  Staging : ks7010 : Fix block comments warninig
  Staging: vt6655: Remove explicit NULL comparison using Coccinelle
  staging: rtl8188eu: core: rtw_xmit: Use macros instead of constants
  staging: rtl8188eu: core: rtw_xmit: Move constant of the right side
  staging: dgnc: Fix lines longer than 80 characters
  Staging: dgnc: constify attribute_group structures
  Staging: most: hdm-dim2: constify attribute_group structures
  ...

7 files changed, 2053 insertions, 4 deletions

diff --git a/drivers/iio/pressure/Kconfig b/drivers/iio/pressure/Kconfig
index 7fa65ab664fb..15cd416365c1 100644
--- a/drivers/iio/pressure/Kconfig
+++ b/drivers/iio/pressure/Kconfig
@@ -185,4 +185,26 @@ config HP206C
 	  This driver can also be built as a module. If so, the module will
 	  be called hp206c.
 
+config ZPA2326
+	tristate "Murata ZPA2326 pressure sensor driver"
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
+	select REGMAP
+	select ZPA2326_I2C if I2C
+	select ZPA2326_SPI if SPI_MASTER
+	help
+	  Say Y here to build support for the Murata ZPA2326 pressure and
+	  temperature sensor.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called zpa2326.
+
+config ZPA2326_I2C
+	tristate
+	select REGMAP_I2C
+
+config ZPA2326_SPI
+	tristate
+	select REGMAP_SPI
+
 endmenu
diff --git a/drivers/iio/pressure/Makefile b/drivers/iio/pressure/Makefile
index 7f395bed5e88..fff77185a5cc 100644
--- a/drivers/iio/pressure/Makefile
+++ b/drivers/iio/pressure/Makefile
@@ -22,6 +22,9 @@ st_pressure-y := st_pressure_core.o
 st_pressure-$(CONFIG_IIO_BUFFER) += st_pressure_buffer.o
 obj-$(CONFIG_T5403) += t5403.o
 obj-$(CONFIG_HP206C) += hp206c.o
+obj-$(CONFIG_ZPA2326) += zpa2326.o
+obj-$(CONFIG_ZPA2326_I2C) += zpa2326_i2c.o
+obj-$(CONFIG_ZPA2326_SPI) += zpa2326_spi.o
 
 obj-$(CONFIG_IIO_ST_PRESS_I2C) += st_pressure_i2c.o
 obj-$(CONFIG_IIO_ST_PRESS_SPI) += st_pressure_spi.o
diff --git a/drivers/iio/pressure/ms5611_core.c b/drivers/iio/pressure/ms5611_core.c
index feb41f82c64a..a74ed1f0c880 100644
--- a/drivers/iio/pressure/ms5611_core.c
+++ b/drivers/iio/pressure/ms5611_core.c
@@ -416,8 +416,7 @@ static int ms5611_init(struct iio_dev *indio_dev)
 	return 0;
 
 err_regulator_disable:
-	if (!IS_ERR_OR_NULL(st->vdd))
-		regulator_disable(st->vdd);
+	regulator_disable(st->vdd);
 	return ret;
 }
 
@@ -425,8 +424,7 @@ static void ms5611_fini(const struct iio_dev *indio_dev)
 {
 	const struct ms5611_state *st = iio_priv(indio_dev);
 
-	if (!IS_ERR_OR_NULL(st->vdd))
-		regulator_disable(st->vdd);
+	regulator_disable(st->vdd);
 }
 
 int ms5611_probe(struct iio_dev *indio_dev, struct device *dev,
diff --git a/drivers/iio/pressure/zpa2326.c b/drivers/iio/pressure/zpa2326.c
new file mode 100644
index 000000000000..19d2eb46fda6
--- /dev/null
+++ b/drivers/iio/pressure/zpa2326.c
@@ -0,0 +1,1735 @@
+/*
+ * Murata ZPA2326 pressure and temperature sensor IIO driver
+ *
+ * Copyright (c) 2016 Parrot S.A.
+ *
+ * Author: Gregor Boirie <gregor.boirie@parrot.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ */
+
+/**
+ * DOC: ZPA2326 theory of operations
+ *
+ * This driver supports %INDIO_DIRECT_MODE and %INDIO_BUFFER_TRIGGERED IIO
+ * modes.
+ * A internal hardware trigger is also implemented to dispatch registered IIO
+ * trigger consumers upon "sample ready" interrupts.
+ *
+ * ZPA2326 hardware supports 2 sampling mode: one shot and continuous.
+ *
+ * A complete one shot sampling cycle gets device out of low power mode,
+ * performs pressure and temperature measurements, then automatically switches
+ * back to low power mode. It is meant for on demand sampling with optimal power
+ * saving at the cost of lower sampling rate and higher software overhead.
+ * This is a natural candidate for IIO read_raw hook implementation
+ * (%INDIO_DIRECT_MODE). It is also used for triggered buffering support to
+ * ensure explicit synchronization with external trigger events
+ * (%INDIO_BUFFER_TRIGGERED).
+ *
+ * The continuous mode works according to a periodic hardware measurement
+ * process continuously pushing samples into an internal hardware FIFO (for
+ * pressure samples only). Measurement cycle completion may be signaled by a
+ * "sample ready" interrupt.
+ * Typical software sequence of operations :
+ * - get device out of low power mode,
+ * - setup hardware sampling period,
+ * - at end of period, upon data ready interrupt: pop pressure samples out of
+ *   hardware FIFO and fetch temperature sample
+ * - when no longer needed, stop sampling process by putting device into
+ *   low power mode.
+ * This mode is used to implement %INDIO_BUFFER_TRIGGERED mode if device tree
+ * declares a valid interrupt line. In this case, the internal hardware trigger
+ * drives acquisition.
+ *
+ * Note that hardware sampling frequency is taken into account only when
+ * internal hardware trigger is attached as the highest sampling rate seems to
+ * be the most energy efficient.
+ *
+ * TODO:
+ *   preset pressure threshold crossing / IIO events ;
+ *   differential pressure sampling ;
+ *   hardware samples averaging.
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/regulator/consumer.h>
+#include <linux/pm_runtime.h>
+#include <linux/regmap.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/trigger.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
+#include "zpa2326.h"
+
+/* 200 ms should be enough for the longest conversion time in one-shot mode. */
+#define ZPA2326_CONVERSION_JIFFIES (HZ / 5)
+
+/* There should be a 1 ms delay (Tpup) after getting out of reset. */
+#define ZPA2326_TPUP_USEC_MIN      (1000)
+#define ZPA2326_TPUP_USEC_MAX      (2000)
+
+/**
+ * struct zpa2326_frequency - Hardware sampling frequency descriptor
+ * @hz : Frequency in Hertz.
+ * @odr: Output Data Rate word as expected by %ZPA2326_CTRL_REG3_REG.
+ */
+struct zpa2326_frequency {
+	int hz;
+	u16 odr;
+};
+
+/*
+ * Keep these in strict ascending order: last array entry is expected to
+ * correspond to the highest sampling frequency.
+ */
+static const struct zpa2326_frequency zpa2326_sampling_frequencies[] = {
+	{ .hz = 1,  .odr = 1 << ZPA2326_CTRL_REG3_ODR_SHIFT },
+	{ .hz = 5,  .odr = 5 << ZPA2326_CTRL_REG3_ODR_SHIFT },
+	{ .hz = 11, .odr = 6 << ZPA2326_CTRL_REG3_ODR_SHIFT },
+	{ .hz = 23, .odr = 7 << ZPA2326_CTRL_REG3_ODR_SHIFT },
+};
+
+/* Return the highest hardware sampling frequency available. */
+static const struct zpa2326_frequency *zpa2326_highest_frequency(void)
+{
+	return &zpa2326_sampling_frequencies[
+		ARRAY_SIZE(zpa2326_sampling_frequencies) - 1];
+}
+
+/**
+ * struct zpa_private - Per-device internal private state
+ * @timestamp:  Buffered samples ready datum.
+ * @regmap:     Underlying I2C / SPI bus adapter used to abstract slave register
+ *              accesses.
+ * @result:     Allows sampling logic to get completion status of operations
+ *              that interrupt handlers perform asynchronously.
+ * @data_ready: Interrupt handler uses this to wake user context up at sampling
+ *              operation completion.
+ * @trigger:    Optional hardware / interrupt driven trigger used to notify
+ *              external devices a new sample is ready.
+ * @waken:      Flag indicating whether or not device has just been powered on.
+ * @irq:        Optional interrupt line: negative or zero if not declared into
+ *              DT, in which case sampling logic keeps polling status register
+ *              to detect completion.
+ * @frequency:  Current hardware sampling frequency.
+ * @vref:       Power / voltage reference.
+ * @vdd:        Power supply.
+ */
+struct zpa2326_private {
+	s64                             timestamp;
+	struct regmap                  *regmap;
+	int                             result;
+	struct completion               data_ready;
+	struct iio_trigger             *trigger;
+	bool                            waken;
+	int                             irq;
+	const struct zpa2326_frequency *frequency;
+	struct regulator               *vref;
+	struct regulator               *vdd;
+};
+
+#define zpa2326_err(_idev, _format, _arg...) \
+	dev_err(_idev->dev.parent, _format, ##_arg)
+
+#define zpa2326_warn(_idev, _format, _arg...) \
+	dev_warn(_idev->dev.parent, _format, ##_arg)
+
+#ifdef DEBUG
+#define zpa2326_dbg(_idev, _format, _arg...) \
+	dev_dbg(_idev->dev.parent, _format, ##_arg)
+#else
+#define zpa2326_dbg(_idev, _format, _arg...)
+#endif
+
+bool zpa2326_isreg_writeable(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case ZPA2326_REF_P_XL_REG:
+	case ZPA2326_REF_P_L_REG:
+	case ZPA2326_REF_P_H_REG:
+	case ZPA2326_RES_CONF_REG:
+	case ZPA2326_CTRL_REG0_REG:
+	case ZPA2326_CTRL_REG1_REG:
+	case ZPA2326_CTRL_REG2_REG:
+	case ZPA2326_CTRL_REG3_REG:
+	case ZPA2326_THS_P_LOW_REG:
+	case ZPA2326_THS_P_HIGH_REG:
+		return true;
+
+	default:
+		return false;
+	}
+}
+EXPORT_SYMBOL_GPL(zpa2326_isreg_writeable);
+
+bool zpa2326_isreg_readable(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case ZPA2326_REF_P_XL_REG:
+	case ZPA2326_REF_P_L_REG:
+	case ZPA2326_REF_P_H_REG:
+	case ZPA2326_DEVICE_ID_REG:
+	case ZPA2326_RES_CONF_REG:
+	case ZPA2326_CTRL_REG0_REG:
+	case ZPA2326_CTRL_REG1_REG:
+	case ZPA2326_CTRL_REG2_REG:
+	case ZPA2326_CTRL_REG3_REG:
+	case ZPA2326_INT_SOURCE_REG:
+	case ZPA2326_THS_P_LOW_REG:
+	case ZPA2326_THS_P_HIGH_REG:
+	case ZPA2326_STATUS_REG:
+	case ZPA2326_PRESS_OUT_XL_REG:
+	case ZPA2326_PRESS_OUT_L_REG:
+	case ZPA2326_PRESS_OUT_H_REG:
+	case ZPA2326_TEMP_OUT_L_REG:
+	case ZPA2326_TEMP_OUT_H_REG:
+		return true;
+
+	default:
+		return false;
+	}
+}
+EXPORT_SYMBOL_GPL(zpa2326_isreg_readable);
+
+bool zpa2326_isreg_precious(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case ZPA2326_INT_SOURCE_REG:
+	case ZPA2326_PRESS_OUT_H_REG:
+		return true;
+
+	default:
+		return false;
+	}
+}
+EXPORT_SYMBOL_GPL(zpa2326_isreg_precious);
+
+/**
+ * zpa2326_enable_device() - Enable device, i.e. get out of low power mode.
+ * @indio_dev: The IIO device associated with the hardware to enable.
+ *
+ * Required to access complete register space and to perform any sampling
+ * or control operations.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_enable_device(const struct iio_dev *indio_dev)
+{
+	int err;
+
+	err = regmap_write(((struct zpa2326_private *)
+			    iio_priv(indio_dev))->regmap,
+			    ZPA2326_CTRL_REG0_REG, ZPA2326_CTRL_REG0_ENABLE);
+	if (err) {
+		zpa2326_err(indio_dev, "failed to enable device (%d)", err);
+		return err;
+	}
+
+	zpa2326_dbg(indio_dev, "enabled");
+
+	return 0;
+}
+
+/**
+ * zpa2326_sleep() - Disable device, i.e. switch to low power mode.
+ * @indio_dev: The IIO device associated with the hardware to disable.
+ *
+ * Only %ZPA2326_DEVICE_ID_REG and %ZPA2326_CTRL_REG0_REG registers may be
+ * accessed once device is in the disabled state.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_sleep(const struct iio_dev *indio_dev)
+{
+	int err;
+
+	err = regmap_write(((struct zpa2326_private *)
+			    iio_priv(indio_dev))->regmap,
+			    ZPA2326_CTRL_REG0_REG, 0);
+	if (err) {
+		zpa2326_err(indio_dev, "failed to sleep (%d)", err);
+		return err;
+	}
+
+	zpa2326_dbg(indio_dev, "sleeping");
+
+	return 0;
+}
+
+/**
+ * zpa2326_reset_device() - Reset device to default hardware state.
+ * @indio_dev: The IIO device associated with the hardware to reset.
+ *
+ * Disable sampling and empty hardware FIFO.
+ * Device must be enabled before reset, i.e. not in low power mode.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_reset_device(const struct iio_dev *indio_dev)
+{
+	int err;
+
+	err = regmap_write(((struct zpa2326_private *)
+			    iio_priv(indio_dev))->regmap,
+			    ZPA2326_CTRL_REG2_REG, ZPA2326_CTRL_REG2_SWRESET);
+	if (err) {
+		zpa2326_err(indio_dev, "failed to reset device (%d)", err);
+		return err;
+	}
+
+	usleep_range(ZPA2326_TPUP_USEC_MIN, ZPA2326_TPUP_USEC_MAX);
+
+	zpa2326_dbg(indio_dev, "reset");
+
+	return 0;
+}
+
+/**
+ * zpa2326_start_oneshot() - Start a single sampling cycle, i.e. in one shot
+ *                           mode.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ *
+ * Device must have been previously enabled and configured for one shot mode.
+ * Device will be switched back to low power mode at end of cycle.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_start_oneshot(const struct iio_dev *indio_dev)
+{
+	int err;
+
+	err = regmap_write(((struct zpa2326_private *)
+			    iio_priv(indio_dev))->regmap,
+			    ZPA2326_CTRL_REG0_REG,
+			    ZPA2326_CTRL_REG0_ENABLE |
+			    ZPA2326_CTRL_REG0_ONE_SHOT);
+	if (err) {
+		zpa2326_err(indio_dev, "failed to start one shot cycle (%d)",
+			    err);
+		return err;
+	}
+
+	zpa2326_dbg(indio_dev, "one shot cycle started");
+
+	return 0;
+}
+
+/**
+ * zpa2326_power_on() - Power on device to allow subsequent configuration.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ * @private:   Internal private state related to @indio_dev.
+ *
+ * Sampling will be disabled, preventing strange things from happening in our
+ * back. Hardware FIFO content will be cleared.
+ * When successful, device will be left in the enabled state to allow further
+ * configuration.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_power_on(const struct iio_dev         *indio_dev,
+			    const struct zpa2326_private *private)
+{
+	int err;
+
+	err = regulator_enable(private->vref);
+	if (err)
+		return err;
+
+	err = regulator_enable(private->vdd);
+	if (err)
+		goto vref;
+
+	zpa2326_dbg(indio_dev, "powered on");
+
+	err = zpa2326_enable_device(indio_dev);
+	if (err)
+		goto vdd;
+
+	err = zpa2326_reset_device(indio_dev);
+	if (err)
+		goto sleep;
+
+	return 0;
+
+sleep:
+	zpa2326_sleep(indio_dev);
+vdd:
+	regulator_disable(private->vdd);
+vref:
+	regulator_disable(private->vref);
+
+	zpa2326_dbg(indio_dev, "powered off");
+
+	return err;
+}
+
+/**
+ * zpa2326_power_off() - Power off device, i.e. disable attached power
+ *                       regulators.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ * @private:   Internal private state related to @indio_dev.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static void zpa2326_power_off(const struct iio_dev         *indio_dev,
+			      const struct zpa2326_private *private)
+{
+	regulator_disable(private->vdd);
+	regulator_disable(private->vref);
+
+	zpa2326_dbg(indio_dev, "powered off");
+}
+
+/**
+ * zpa2326_config_oneshot() - Setup device for one shot / on demand mode.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ * @irq:       Optional interrupt line the hardware uses to notify new data
+ *             samples are ready. Negative or zero values indicate no interrupts
+ *             are available, meaning polling is required.
+ *
+ * Output Data Rate is configured for the highest possible rate so that
+ * conversion time and power consumption are reduced to a minimum.
+ * Note that hardware internal averaging machinery (not implemented in this
+ * driver) is not applicable in this mode.
+ *
+ * Device must have been previously enabled before calling
+ * zpa2326_config_oneshot().
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_config_oneshot(const struct iio_dev *indio_dev,
+				  int                   irq)
+{
+	struct regmap                  *regs = ((struct zpa2326_private *)
+						iio_priv(indio_dev))->regmap;
+	const struct zpa2326_frequency *freq = zpa2326_highest_frequency();
+	int                             err;
+
+	/* Setup highest available Output Data Rate for one shot mode. */
+	err = regmap_write(regs, ZPA2326_CTRL_REG3_REG, freq->odr);
+	if (err)
+		return err;
+
+	if (irq > 0) {
+		/* Request interrupt when new sample is available. */
+		err = regmap_write(regs, ZPA2326_CTRL_REG1_REG,
+				   (u8)~ZPA2326_CTRL_REG1_MASK_DATA_READY);
+
+		if (err) {
+			dev_err(indio_dev->dev.parent,
+				"failed to setup one shot mode (%d)", err);
+			return err;
+		}
+	}
+
+	zpa2326_dbg(indio_dev, "one shot mode setup @%dHz", freq->hz);
+
+	return 0;
+}
+
+/**
+ * zpa2326_clear_fifo() - Clear remaining entries in hardware FIFO.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ * @min_count: Number of samples present within hardware FIFO.
+ *
+ * @min_count argument is a hint corresponding to the known minimum number of
+ * samples currently living in the FIFO. This allows to reduce the number of bus
+ * accesses by skipping status register read operation as long as we know for
+ * sure there are still entries left.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_clear_fifo(const struct iio_dev *indio_dev,
+			      unsigned int          min_count)
+{
+	struct regmap *regs = ((struct zpa2326_private *)
+			       iio_priv(indio_dev))->regmap;
+	int            err;
+	unsigned int   val;
+
+	if (!min_count) {
+		/*
+		 * No hint: read status register to determine whether FIFO is
+		 * empty or not.
+		 */
+		err = regmap_read(regs, ZPA2326_STATUS_REG, &val);
+
+		if (err < 0)
+			goto err;
+
+		if (val & ZPA2326_STATUS_FIFO_E)
+			/* Fifo is empty: nothing to trash. */
+			return 0;
+	}
+
+	/* Clear FIFO. */
+	do {
+		/*
+		 * A single fetch from pressure MSB register is enough to pop
+		 * values out of FIFO.
+		 */
+		err = regmap_read(regs, ZPA2326_PRESS_OUT_H_REG, &val);
+		if (err < 0)
+			goto err;
+
+		if (min_count) {
+			/*
+			 * We know for sure there are at least min_count entries
+			 * left in FIFO. Skip status register read.
+			 */
+			min_count--;
+			continue;
+		}
+
+		err = regmap_read(regs, ZPA2326_STATUS_REG, &val);
+		if (err < 0)
+			goto err;
+
+	} while (!(val & ZPA2326_STATUS_FIFO_E));
+
+	zpa2326_dbg(indio_dev, "FIFO cleared");
+
+	return 0;
+
+err:
+	zpa2326_err(indio_dev, "failed to clear FIFO (%d)", err);
+
+	return err;
+}
+
+/**
+ * zpa2326_dequeue_pressure() - Retrieve the most recent pressure sample from
+ *                              hardware FIFO.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ * @pressure:  Sampled pressure output.
+ *
+ * Note that ZPA2326 hardware FIFO stores pressure samples only.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_dequeue_pressure(const struct iio_dev *indio_dev,
+				    u32                  *pressure)
+{
+	struct regmap *regs = ((struct zpa2326_private *)
+			       iio_priv(indio_dev))->regmap;
+	unsigned int   val;
+	int            err;
+	int            cleared = -1;
+
+	err = regmap_read(regs, ZPA2326_STATUS_REG, &val);
+	if (err < 0)
+		return err;
+
+	*pressure = 0;
+
+	if (val & ZPA2326_STATUS_P_OR) {
+		/*
+		 * Fifo overrun : first sample dequeued from FIFO is the
+		 * newest.
+		 */
+		zpa2326_warn(indio_dev, "FIFO overflow");
+
+		err = regmap_bulk_read(regs, ZPA2326_PRESS_OUT_XL_REG, pressure,
+				       3);
+		if (err)
+			return err;
+
+#define ZPA2326_FIFO_DEPTH (16U)
+		/* Hardware FIFO may hold no more than 16 pressure samples. */
+		return zpa2326_clear_fifo(indio_dev, ZPA2326_FIFO_DEPTH - 1);
+	}
+
+	/*
+	 * Fifo has not overflown : retrieve newest sample. We need to pop
+	 * values out until FIFO is empty : last fetched pressure is the newest.
+	 * In nominal cases, we should find a single queued sample only.
+	 */
+	do {
+		err = regmap_bulk_read(regs, ZPA2326_PRESS_OUT_XL_REG, pressure,
+				       3);
+		if (err)
+			return err;
+
+		err = regmap_read(regs, ZPA2326_STATUS_REG, &val);
+		if (err < 0)
+			return err;
+
+		cleared++;
+	} while (!(val & ZPA2326_STATUS_FIFO_E));
+
+	if (cleared)
+		/*
+		 * Samples were pushed by hardware during previous rounds but we
+		 * didn't consume them fast enough: inform user.
+		 */
+		zpa2326_dbg(indio_dev, "cleared %d FIFO entries", cleared);
+
+	return 0;
+}
+
+/**
+ * zpa2326_fill_sample_buffer() - Enqueue new channel samples to IIO buffer.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ * @private:   Internal private state related to @indio_dev.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_fill_sample_buffer(struct iio_dev               *indio_dev,
+				      const struct zpa2326_private *private)
+{
+	struct {
+		u32 pressure;
+		u16 temperature;
+		u64 timestamp;
+	}   sample;
+	int err;
+
+	if (test_bit(0, indio_dev->active_scan_mask)) {
+		/* Get current pressure from hardware FIFO. */
+		err = zpa2326_dequeue_pressure(indio_dev, &sample.pressure);
+		if (err) {
+			zpa2326_warn(indio_dev, "failed to fetch pressure (%d)",
+				     err);
+			return err;
+		}
+	}
+
+	if (test_bit(1, indio_dev->active_scan_mask)) {
+		/* Get current temperature. */
+		err = regmap_bulk_read(private->regmap, ZPA2326_TEMP_OUT_L_REG,
+				       &sample.temperature, 2);
+		if (err) {
+			zpa2326_warn(indio_dev,
+				     "failed to fetch temperature (%d)", err);
+			return err;
+		}
+	}
+
+	/*
+	 * Now push samples using timestamp stored either :
+	 *   - by hardware interrupt handler if interrupt is available: see
+	 *     zpa2326_handle_irq(),
+	 *   - or oneshot completion polling machinery : see
+	 *     zpa2326_trigger_handler().
+	 */
+	zpa2326_dbg(indio_dev, "filling raw samples buffer");
+
+	iio_push_to_buffers_with_timestamp(indio_dev, &sample,
+					   private->timestamp);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM
+static int zpa2326_runtime_suspend(struct device *parent)
+{
+	const struct iio_dev *indio_dev = dev_get_drvdata(parent);
+
+	if (pm_runtime_autosuspend_expiration(parent))
+		/* Userspace changed autosuspend delay. */
+		return -EAGAIN;
+
+	zpa2326_power_off(indio_dev, iio_priv(indio_dev));
+
+	return 0;
+}
+
+static int zpa2326_runtime_resume(struct device *parent)
+{
+	const struct iio_dev *indio_dev = dev_get_drvdata(parent);
+
+	return zpa2326_power_on(indio_dev, iio_priv(indio_dev));
+}
+
+const struct dev_pm_ops zpa2326_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
+				pm_runtime_force_resume)
+	SET_RUNTIME_PM_OPS(zpa2326_runtime_suspend, zpa2326_runtime_resume,
+			   NULL)
+};
+EXPORT_SYMBOL_GPL(zpa2326_pm_ops);
+
+/**
+ * zpa2326_resume() - Request the PM layer to power supply the device.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ *
+ * Return:
+ *  < 0 - a negative error code meaning failure ;
+ *    0 - success, device has just been powered up ;
+ *    1 - success, device was already powered.
+ */
+static int zpa2326_resume(const struct iio_dev *indio_dev)
+{
+	int err;
+
+	err = pm_runtime_get_sync(indio_dev->dev.parent);
+	if (err < 0)
+		return err;
+
+	if (err > 0) {
+		/*
+		 * Device was already power supplied: get it out of low power
+		 * mode and inform caller.
+		 */
+		zpa2326_enable_device(indio_dev);
+		return 1;
+	}
+
+	/* Inform caller device has just been brought back to life. */
+	return 0;
+}
+
+/**
+ * zpa2326_suspend() - Schedule a power down using autosuspend feature of PM
+ *                     layer.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ *
+ * Device is switched to low power mode at first to save power even when
+ * attached regulator is a "dummy" one.
+ */
+static void zpa2326_suspend(struct iio_dev *indio_dev)
+{
+	struct device *parent = indio_dev->dev.parent;
+
+	zpa2326_sleep(indio_dev);
+
+	pm_runtime_mark_last_busy(parent);
+	pm_runtime_put_autosuspend(parent);
+}
+
+static void zpa2326_init_runtime(struct device *parent)
+{
+	pm_runtime_get_noresume(parent);
+	pm_runtime_set_active(parent);
+	pm_runtime_enable(parent);
+	pm_runtime_set_autosuspend_delay(parent, 1000);
+	pm_runtime_use_autosuspend(parent);
+	pm_runtime_mark_last_busy(parent);
+	pm_runtime_put_autosuspend(parent);
+}
+
+static void zpa2326_fini_runtime(struct device *parent)
+{
+	pm_runtime_disable(parent);
+	pm_runtime_set_suspended(parent);
+}
+#else /* !CONFIG_PM */
+static int zpa2326_resume(const struct iio_dev *indio_dev)
+{
+	zpa2326_enable_device(indio_dev);
+
+	return 0;
+}
+
+static void zpa2326_suspend(struct iio_dev *indio_dev)
+{
+	zpa2326_sleep(indio_dev);
+}
+
+#define zpa2326_init_runtime(_parent)
+#define zpa2326_fini_runtime(_parent)
+#endif /* !CONFIG_PM */
+
+/**
+ * zpa2326_handle_irq() - Process hardware interrupts.
+ * @irq:  Interrupt line the hardware uses to notify new data has arrived.
+ * @data: The IIO device associated with the sampling hardware.
+ *
+ * Timestamp buffered samples as soon as possible then schedule threaded bottom
+ * half.
+ *
+ * Return: Always successful.
+ */
+static irqreturn_t zpa2326_handle_irq(int irq, void *data)
+{
+	struct iio_dev *indio_dev = (struct iio_dev *)data;
+
+	if (iio_buffer_enabled(indio_dev)) {
+		/* Timestamping needed for buffered sampling only. */
+		((struct zpa2326_private *)
+		 iio_priv(indio_dev))->timestamp = iio_get_time_ns(indio_dev);
+	}
+
+	return IRQ_WAKE_THREAD;
+}
+
+/**
+ * zpa2326_handle_threaded_irq() - Interrupt bottom-half handler.
+ * @irq:  Interrupt line the hardware uses to notify new data has arrived.
+ * @data: The IIO device associated with the sampling hardware.
+ *
+ * Mainly ensures interrupt is caused by a real "new sample available"
+ * condition. This relies upon the ability to perform blocking / sleeping bus
+ * accesses to slave's registers. This is why zpa2326_handle_threaded_irq() is
+ * called from within a thread, i.e. not called from hard interrupt context.
+ *
+ * When device is using its own internal hardware trigger in continuous sampling
+ * mode, data are available into hardware FIFO once interrupt has occurred. All
+ * we have to do is to dispatch the trigger, which in turn will fetch data and
+ * fill IIO buffer.
+ *
+ * When not using its own internal hardware trigger, the device has been
+ * configured in one-shot mode either by an external trigger or the IIO read_raw
+ * hook. This means one of the latter is currently waiting for sampling
+ * completion, in which case we must simply wake it up.
+ *
+ * See zpa2326_trigger_handler().
+ *
+ * Return:
+ *   %IRQ_NONE - no consistent interrupt happened ;
+ *   %IRQ_HANDLED - there was new samples available.
+ */
+static irqreturn_t zpa2326_handle_threaded_irq(int irq, void *data)
+{
+	struct iio_dev         *indio_dev = (struct iio_dev *)data;
+	struct zpa2326_private *priv = iio_priv(indio_dev);
+	unsigned int            val;
+	bool                    cont;
+	irqreturn_t             ret = IRQ_NONE;
+
+	/*
+	 * Are we using our own internal trigger in triggered buffer mode, i.e.,
+	 * currently working in continuous sampling mode ?
+	 */
+	cont = (iio_buffer_enabled(indio_dev) &&
+		iio_trigger_using_own(indio_dev));
+
+	/*
+	 * Device works according to a level interrupt scheme: reading interrupt
+	 * status de-asserts interrupt line.
+	 */
+	priv->result = regmap_read(priv->regmap, ZPA2326_INT_SOURCE_REG, &val);
+	if (priv->result < 0) {
+		if (cont)
+			return IRQ_NONE;
+
+		goto complete;
+	}
+
+	/* Data ready is the only interrupt source we requested. */
+	if (!(val & ZPA2326_INT_SOURCE_DATA_READY)) {
+		/*
+		 * Interrupt happened but no new sample available: likely caused
+		 * by spurious interrupts, in which case, returning IRQ_NONE
+		 * allows to benefit from the generic spurious interrupts
+		 * handling.
+		 */
+		zpa2326_warn(indio_dev, "unexpected interrupt status %02x",
+			     val);
+
+		if (cont)
+			return IRQ_NONE;
+
+		priv->result = -ENODATA;
+		goto complete;
+	}
+
+	/* New sample available: dispatch internal trigger consumers. */
+	iio_trigger_poll_chained(priv->trigger);
+
+	if (cont)
+		/*
+		 * Internal hardware trigger has been scheduled above : it will
+		 * fetch data on its own.
+		 */
+		return IRQ_HANDLED;
+
+	ret = IRQ_HANDLED;
+
+complete:
+	/*
+	 * Wake up direct or externaly triggered buffer mode waiters: see
+	 * zpa2326_sample_oneshot() and zpa2326_trigger_handler().
+	 */
+	complete(&priv->data_ready);
+
+	return ret;
+}
+
+/**
+ * zpa2326_wait_oneshot_completion() - Wait for oneshot data ready interrupt.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ * @private:   Internal private state related to @indio_dev.