[PATCH v3 06/11] IIO: ADC: add stm32 DFSDM support for PDM microphone

From: Arnaud Pouliquen <arnaud.pouliquen@st.com>
To: Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Jonathan Cameron <jic23@kernel.org>,
	Hartmut Knaack <knaack.h@gmx.de>,
	Lars-Peter Clausen <lars@metafoo.de>,
	Peter Meerwald-Stadler <pmeerw@pmeerw.net>,
	Jaroslav Kysela <perex@perex.cz>, Takashi Iwai <tiwai@suse.com>,
	Liam Girdwood <lgirdwood@gmail.com>,
	Mark Brown <broonie@kernel.org>
Cc: devicetree@vger.kernel.org, alsa-devel@alsa-project.org,
	olivier moysan <olivier.moysan@st.com>,
	kernel@stlinux.com, linux-iio@vger.kernel.org,
	arnaud.pouliquen@st.com,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	linux-arm-kernel@lists.infradead.org,
	Alexandre Torgue <alexandre.torgue@st.com>
Subject: [PATCH v3 06/11] IIO: ADC: add stm32 DFSDM support for PDM microphone
Date: Fri, 17 Mar 2017 15:08:19 +0100	[thread overview]
Message-ID: <1489759704-30217-7-git-send-email-arnaud.pouliquen@st.com> (raw)
In-Reply-To: <1489759704-30217-1-git-send-email-arnaud.pouliquen@st.com>

Add DFSDM driver to handle PDM audio microphones.

Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
---
 drivers/iio/adc/Kconfig                   |  13 +
 drivers/iio/adc/Makefile                  |   1 +
 drivers/iio/adc/stm32-dfsdm-audio.c       | 720 ++++++++++++++++++++++++++++++
 include/linux/iio/adc/stm32-dfsdm-audio.h |  41 ++
 4 files changed, 775 insertions(+)
 create mode 100644 drivers/iio/adc/stm32-dfsdm-audio.c
 create mode 100644 include/linux/iio/adc/stm32-dfsdm-audio.h

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 3e0eb11..c108933 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -478,6 +478,19 @@ config STM32_DFSDM_ADC
 	  This driver can also be built as a module.  If so, the module
 	  will be called stm32-dfsdm-adc.
 
+config STM32_DFSDM_AUDIO
+	tristate "STMicroelectronics STM32 dfsdm audio
+	depends on (ARCH_STM32 && OF) || COMPILE_TEST
+	select STM32_DFSDM_CORE
+	select REGMAP_MMIO
+	select IIO_BUFFER_DMAENGINE
+	help
+	  Select this option to support Audio PDM micophone for
+	  STMicroelectronics  STM32 digital filter for sigma delta converter.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called stm32-dfsdm-audio.
+
 config STX104
 	tristate "Apex Embedded Systems STX104 driver"
 	depends on X86 && ISA_BUS_API
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 161f271..79f975d 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -44,6 +44,7 @@ obj-$(CONFIG_STX104) += stx104.o
 obj-$(CONFIG_STM32_ADC_CORE) += stm32-adc-core.o
 obj-$(CONFIG_STM32_ADC) += stm32-adc.o
 obj-$(CONFIG_STM32_DFSDM_ADC) += stm32-dfsdm-adc.o
+obj-$(CONFIG_STM32_DFSDM_AUDIO) += stm32-dfsdm-audio.o
 obj-$(CONFIG_STM32_DFSDM_CORE) += stm32-dfsdm-core.o
 obj-$(CONFIG_TI_ADC081C) += ti-adc081c.o
 obj-$(CONFIG_TI_ADC0832) += ti-adc0832.o
diff --git a/drivers/iio/adc/stm32-dfsdm-audio.c b/drivers/iio/adc/stm32-dfsdm-audio.c
new file mode 100644
index 0000000..115ef8f
--- /dev/null
+++ b/drivers/iio/adc/stm32-dfsdm-audio.c
@@ -0,0 +1,720 @@
+/*
+ * This file is the ADC part of of the STM32 DFSDM driver
+ *
+ * Copyright (C) 2017, STMicroelectronics - All Rights Reserved
+ * Author: Arnaud Pouliquen <arnaud.pouliquen@st.com>.
+ *
+ * License type: GPLv2
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/dmaengine.h>
+#include <linux/dma-mapping.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+#include <linux/iio/buffer.h>
+#include <linux/iio/hw_consumer.h>
+#include <linux/iio/sysfs.h>
+#include <linux/iio/trigger.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
+
+#include "stm32-dfsdm.h"
+
+#define DFSDM_DMA_BUFFER_SIZE (4 * PAGE_SIZE)
+
+struct stm32_dfsdm_audio {
+	struct stm32_dfsdm *dfsdm;
+	unsigned int fl_id;
+	unsigned int ch_id;
+	unsigned int spi_freq;  /* SPI bus clock frequency */
+	unsigned int sample_freq; /* Sample frequency after filter decimation */
+
+	u8 *rx_buf;
+	unsigned int bufi; /* Buffer current position */
+	unsigned int buf_sz; /* Buffer size */
+
+	struct dma_chan	*dma_chan;
+	dma_addr_t dma_buf;
+
+	int (*cb)(const void *data, size_t size, void *cb_priv);
+	void *cb_priv;
+};
+
+const char *stm32_dfsdm_spi_trigger = DFSDM_SPI_TRIGGER_NAME;
+
+static ssize_t dfsdm_audio_get_rate(struct iio_dev *indio_dev, uintptr_t priv,
+				    const struct iio_chan_spec *chan, char *buf)
+{
+	struct stm32_dfsdm_audio *pdmc = iio_priv(indio_dev);
+
+	return snprintf(buf, PAGE_SIZE, "%d\n", pdmc->sample_freq);
+}
+
+static ssize_t dfsdm_audio_set_rate(struct iio_dev *indio_dev, uintptr_t priv,
+				    const struct iio_chan_spec *chan,
+				    const char *buf, size_t len)
+{
+	struct stm32_dfsdm_audio *pdmc = iio_priv(indio_dev);
+	struct stm32_dfsdm_filter *fl = &pdmc->dfsdm->fl_list[pdmc->fl_id];
+	struct stm32_dfsdm_channel *ch = &pdmc->dfsdm->ch_list[pdmc->ch_id];
+	unsigned int spi_freq = pdmc->spi_freq;
+	unsigned int sample_freq;
+	int ret;
+
+	ret = kstrtoint(buf, 0, &sample_freq);
+	if (ret)
+		return ret;
+
+	dev_dbg(&indio_dev->dev, "Requested sample_freq :%d\n", sample_freq);
+	if (!sample_freq)
+		return -EINVAL;
+
+	if (ch->src != DFSDM_CHANNEL_SPI_CLOCK_EXTERNAL)
+		spi_freq = pdmc->dfsdm->spi_master_freq;
+
+	if (spi_freq % sample_freq)
+		dev_warn(&indio_dev->dev, "Sampling rate not accurate (%d)\n",
+			 spi_freq / (spi_freq / sample_freq));
+
+	ret = stm32_dfsdm_set_osrs(fl, 0, (spi_freq / sample_freq));
+	if (ret < 0) {
+		dev_err(&indio_dev->dev,
+			"Not able to find filter parameter that match!\n");
+		return ret;
+	}
+	pdmc->sample_freq = sample_freq;
+
+	return len;
+}
+
+static ssize_t dfsdm_audio_get_spiclk(struct iio_dev *indio_dev, uintptr_t priv,
+				      const struct iio_chan_spec *chan,
+				      char *buf)
+{
+	struct stm32_dfsdm_audio *pdmc = iio_priv(indio_dev);
+
+	return snprintf(buf, PAGE_SIZE, "%d\n", pdmc->spi_freq);
+}
+
+static ssize_t dfsdm_audio_set_spiclk(struct iio_dev *indio_dev, uintptr_t priv,
+				      const struct iio_chan_spec *chan,
+				      const char *buf, size_t len)
+{
+	struct stm32_dfsdm_audio *pdmc = iio_priv(indio_dev);
+	struct stm32_dfsdm_filter *fl = &pdmc->dfsdm->fl_list[pdmc->fl_id];
+	struct stm32_dfsdm_channel *ch = &pdmc->dfsdm->ch_list[pdmc->ch_id];
+	unsigned int sample_freq = pdmc->sample_freq;
+	unsigned int spi_freq;
+	int ret;
+
+	/* If DFSDM is master on SPI, SPI freq can not be updated */
+	if (ch->src != DFSDM_CHANNEL_SPI_CLOCK_EXTERNAL)
+		return -EPERM;
+
+	ret = kstrtoint(buf, 0, &spi_freq);
+	if (ret)
+		return ret;
+
+	dev_dbg(&indio_dev->dev, "Requested frequency :%d\n", spi_freq);
+	if (!spi_freq)
+		return -EINVAL;
+
+	if (sample_freq) {
+		if (spi_freq % sample_freq)
+			dev_warn(&indio_dev->dev,
+				 "Sampling rate not accurate (%d)\n",
+				 spi_freq / (spi_freq / sample_freq));
+
+		ret = stm32_dfsdm_set_osrs(fl, 0, (spi_freq / sample_freq));
+		if (ret < 0) {
+			dev_err(&indio_dev->dev,
+				"No filter parameters that match!\n");
+			return ret;
+		}
+	}
+	pdmc->spi_freq = spi_freq;
+
+	return len;
+}
+
+/*
+ * Define external info for SPI Frequency and audio sampling rate that can be
+ * configured by ASoC driver through consumer.h API
+ */
+static const struct iio_chan_spec_ext_info dfsdm_adc_ext_info[] = {
+	/* filter oversampling: Post filter oversampling ratio */
+	{
+		.name = "audio_sampling_rate",
+		.shared = IIO_SHARED_BY_TYPE,
+		.read = dfsdm_audio_get_rate,
+		.write = dfsdm_audio_set_rate,
+	},
+	/* data_right_bit_shift : Filter output data shifting */
+	{
+		.name = "spi_clk_freq",
+		.shared = IIO_SHARED_BY_TYPE,
+		.read = dfsdm_audio_get_spiclk,
+		.write = dfsdm_audio_set_spiclk,
+	},
+	{},
+};
+
+static int stm32_dfsdm_start_conv(struct stm32_dfsdm_audio *pdmc, bool single)
+{
+	struct regmap *regmap = pdmc->dfsdm->regmap;
+	int ret;
+
+	ret = stm32_dfsdm_start_dfsdm(pdmc->dfsdm);
+	if (ret < 0)
+		return ret;
+
+	ret = stm32_dfsdm_start_channel(pdmc->dfsdm, pdmc->ch_id);
+	if (ret < 0)
+		goto stop_dfsdm;
+
+	ret = stm32_dfsdm_filter_configure(pdmc->dfsdm, pdmc->fl_id,
+					   pdmc->ch_id);
+	if (ret < 0)
+		goto stop_channels;
+
+	/* Enable DMA transfer*/
+	ret = regmap_update_bits(regmap, DFSDM_CR1(pdmc->fl_id),
+				 DFSDM_CR1_RDMAEN_MASK, DFSDM_CR1_RDMAEN(1));
+	if (ret < 0)
+		return ret;
+
+	/* Enable conversion triggered by SPI clock*/
+	ret = regmap_update_bits(regmap, DFSDM_CR1(pdmc->fl_id),
+				 DFSDM_CR1_RCONT_MASK,  DFSDM_CR1_RCONT(1));
+	if (ret < 0)
+		return ret;
+
+	ret = stm32_dfsdm_start_filter(pdmc->dfsdm, pdmc->fl_id);
+	if (ret < 0)
+		goto stop_channels;
+
+	return 0;
+
+stop_channels:
+	stm32_dfsdm_stop_channel(pdmc->dfsdm, pdmc->fl_id);
+stop_dfsdm:
+	stm32_dfsdm_stop_dfsdm(pdmc->dfsdm);
+
+	return ret;
+}
+
+static void stm32_dfsdm_stop_conv(struct stm32_dfsdm_audio *pdmc)
+{
+	stm32_dfsdm_stop_filter(pdmc->dfsdm, pdmc->fl_id);
+
+	stm32_dfsdm_stop_channel(pdmc->dfsdm, pdmc->ch_id);
+
+	stm32_dfsdm_stop_dfsdm(pdmc->dfsdm);
+}
+
+static int stm32_dfsdm_set_watermark(struct iio_dev *indio_dev,
+				     unsigned int val)
+{
+	struct stm32_dfsdm_audio *pdmc = iio_priv(indio_dev);
+	unsigned int watermark = DFSDM_DMA_BUFFER_SIZE / 2;
+
+	/*
+	 * DMA cyclic transfers are used, buffer is split into two periods.
+	 * There should be :
+	 * - always one buffer (period) DMA is working on
+	 * - one buffer (period) driver pushed to ASoC side ().
+	 */
+	watermark = min(watermark, val * (unsigned int)(sizeof(u32)));
+	pdmc->buf_sz = watermark * 2;
+
+	return 0;
+}
+
+int stm32_dfsdm_validate_trigger(struct iio_dev *indio_dev,
+				 struct iio_trigger *trig)
+{
+	if (!strcmp(stm32_dfsdm_spi_trigger, trig->name))
+		return 0;
+
+	return -EINVAL;
+}
+
+static const struct iio_info stm32_dfsdm_info_pdmc = {
+	.hwfifo_set_watermark = stm32_dfsdm_set_watermark,
+	.driver_module = THIS_MODULE,
+	.validate_trigger = stm32_dfsdm_validate_trigger,
+};
+
+static irqreturn_t stm32_dfsdm_irq(int irq, void *arg)
+{
+	struct stm32_dfsdm_audio *pdmc = arg;
+	struct iio_dev *indio_dev = iio_priv_to_dev(pdmc);
+	struct regmap *regmap = pdmc->dfsdm->regmap;
+	unsigned int status;
+
+	regmap_read(regmap, DFSDM_ISR(pdmc->fl_id), &status);
+
+	if (status & DFSDM_ISR_ROVRF_MASK) {
+		dev_err(&indio_dev->dev, "Unexpected Conversion overflow\n");
+		regmap_update_bits(regmap, DFSDM_ICR(pdmc->fl_id),
+				   DFSDM_ICR_CLRROVRF_MASK,
+				   DFSDM_ICR_CLRROVRF_MASK);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static unsigned int stm32_dfsdm_audio_avail_data(struct stm32_dfsdm_audio *pdmc)
+{
+	struct dma_tx_state state;
+	enum dma_status status;
+
+	status = dmaengine_tx_status(pdmc->dma_chan,
+				     pdmc->dma_chan->cookie,
+				     &state);
+	if (status == DMA_IN_PROGRESS) {
+		/* Residue is size in bytes from end of buffer */
+		unsigned int i = pdmc->buf_sz - state.residue;
+		unsigned int size;
+
+		/* Return available bytes */
+		if (i >= pdmc->bufi)
+			size = i - pdmc->bufi;
+		else
+			size = pdmc->buf_sz + i - pdmc->bufi;
+
+		return size;
+	}
+
+	return 0;
+}
+
+static void stm32_dfsdm_audio_dma_buffer_done(void *data)
+{
+	struct iio_dev *indio_dev = data;
+
+	iio_trigger_poll_chained(indio_dev->trig);
+}
+
+static int stm32_dfsdm_audio_dma_start(struct iio_dev *indio_dev)
+{
+	struct stm32_dfsdm_audio *pdmc = iio_priv(indio_dev);
+	struct dma_async_tx_descriptor *desc;
+	dma_cookie_t cookie;
+	int ret;
+
+	if (!pdmc->dma_chan)
+		return -EINVAL;
+
+	dev_dbg(&indio_dev->dev, "%s size=%d watermark=%d\n", __func__,
+		pdmc->buf_sz, pdmc->buf_sz / 2);
+
+	/* Prepare a DMA cyclic transaction */
+	desc = dmaengine_prep_dma_cyclic(pdmc->dma_chan,
+					 pdmc->dma_buf,
+					 pdmc->buf_sz, pdmc->buf_sz / 2,
+					 DMA_DEV_TO_MEM,
+					 DMA_PREP_INTERRUPT);
+	if (!desc)
+		return -EBUSY;
+
+	desc->callback = stm32_dfsdm_audio_dma_buffer_done;
+	desc->callback_param = indio_dev;
+
+	cookie = dmaengine_submit(desc);
+	ret = dma_submit_error(cookie);
+	if (ret) {
+		dmaengine_terminate_all(pdmc->dma_chan);
+		return ret;
+	}
+
+	/* Issue pending DMA requests */
+	dma_async_issue_pending(pdmc->dma_chan);
+
+	return 0;
+}
+
+static int stm32_dfsdm_postenable(struct iio_dev *indio_dev)
+{
+	struct stm32_dfsdm_audio *pdmc = iio_priv(indio_dev);
+	int ret;
+
+	dev_dbg(&indio_dev->dev, "%s\n", __func__);
+	/* Reset pdmc buffer index */
+	pdmc->bufi = 0;
+
+	ret = stm32_dfsdm_start_conv(pdmc, false);
+	if (ret) {
+		dev_err(&indio_dev->dev, "Can't start conversion\n");
+		return ret;
+	}
+
+	ret = stm32_dfsdm_audio_dma_start(indio_dev);
+	if (ret) {
+		dev_err(&indio_dev->dev, "Can't start DMA\n");
+		goto err_stop_conv;
+	}
+
+	ret = iio_triggered_buffer_postenable(indio_dev);
+	if (ret < 0) {
+		dev_err(&indio_dev->dev, "%s :%d\n", __func__, __LINE__);
+		goto err_stop_dma;
+	}
+
+	return 0;
+
+err_stop_dma:
+	if (pdmc->dma_chan)
+		dmaengine_terminate_all(pdmc->dma_chan);
+err_stop_conv:
+	stm32_dfsdm_stop_conv(pdmc);
+
+	return ret;
+}
+
+static int stm32_dfsdm_predisable(struct iio_dev *indio_dev)
+{
+	struct stm32_dfsdm_audio *pdmc = iio_priv(indio_dev);
+	int ret;
+
+	dev_dbg(&indio_dev->dev, "%s\n", __func__);
+	ret = iio_triggered_buffer_predisable(indio_dev);
+	if (ret < 0)
+		dev_err(&indio_dev->dev, "Predisable failed\n");
+
+	if (pdmc->dma_chan)
+		dmaengine_terminate_all(pdmc->dma_chan);
+
+	stm32_dfsdm_stop_conv(pdmc);
+
+	return 0;
+}
+
+static const struct iio_buffer_setup_ops stm32_dfsdm_buffer_setup_ops = {
+	.postenable = &stm32_dfsdm_postenable,
+	.predisable = &stm32_dfsdm_predisable,
+};
+
+static irqreturn_t stm32_dfsdm_audio_trigger_handler(int irq, void *p)
+{
+	struct iio_poll_func *pf = p;
+	struct iio_dev *indio_dev = pf->indio_dev;
+	struct stm32_dfsdm_audio *pdmc = iio_priv(indio_dev);
+	size_t old_pos;
+	int available = stm32_dfsdm_audio_avail_data(pdmc);
+
+	/*
+	 * Buffer interface is not support cyclic DMA buffer,and offer only
+	 * an interface to push data samples per samples.
+	 * For this reason iio_push_to_buffers_with_timestamp in not used
+	 * and interface is hacked using a private callback registered by ASoC.
+	 * This should be a temporary solution waiting a cyclic DMA engine
+	 * support in IIO.
+	 */
+
+	dev_dbg(&indio_dev->dev, "%s: pos = %d, available = %d\n", __func__,
+		pdmc->bufi, available);
+	old_pos = pdmc->bufi;
+	while (available >= indio_dev->scan_bytes) {
+		u32 *buffer = (u32 *)&pdmc->rx_buf[pdmc->bufi];
+
+		/* Mask 8 LSB that contains the channel ID */
+		*buffer &= 0xFFFFFF00;
+		available -= indio_dev->scan_bytes;
+		pdmc->bufi += indio_dev->scan_bytes;
+		if (pdmc->bufi >= pdmc->buf_sz) {
+			if (pdmc->cb)
+				pdmc->cb(&pdmc->rx_buf[old_pos],
+					 pdmc->buf_sz - old_pos, pdmc->cb_priv);
+			pdmc->bufi = 0;
+			old_pos = 0;
+		}
+	}
+	if (pdmc->cb)
+		pdmc->cb(&pdmc->rx_buf[old_pos], pdmc->bufi - old_pos,
+				pdmc->cb_priv);
+
+	iio_trigger_notify_done(indio_dev->trig);
+
+	return IRQ_HANDLED;
+}
+
+/**
+ * stm32_dfsdm_get_buff_cb - register a callback
+ *	that will be called when DMA transfer period is achieved.
+ *
+ * @iio_dev: Handle to IIO device.
+ * @cb: pointer to callback function.
+ *	@data: pointer to data buffer
+ *	@size: size in byte of the data buffer
+ *	@private: pointer to consumer private structure
+ * @private: pointer to consumer private structure
+ */
+int stm32_dfsdm_get_buff_cb(struct iio_dev *iio_dev,
+			    int (*cb)(const void *data, size_t size,
+				      void *private),
+			    void *private)
+{
+	struct stm32_dfsdm_audio *pdmc;
+
+	if (!iio_dev)
+		return -EINVAL;
+	pdmc = iio_priv(iio_dev);
+
+	if (iio_dev !=  iio_priv_to_dev(pdmc))
+		return -EINVAL;
+
+	pdmc->cb = cb;
+	pdmc->cb_priv = private;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(stm32_dfsdm_get_buff_cb);
+
+/**
+ * stm32_dfsdm_release_buff_cb - unregister buffer callback
+ *
+ * @iio_dev: Handle to IIO device.
+ */
+int stm32_dfsdm_release_buff_cb(struct iio_dev *iio_dev)
+{
+	struct stm32_dfsdm_audio *pdmc;
+
+	if (!iio_dev)
+		return -EINVAL;
+	pdmc = iio_priv(iio_dev);
+
+	if (iio_dev !=  iio_priv_to_dev(pdmc))
+		return -EINVAL;
+	pdmc->cb = NULL;
+	pdmc->cb_priv = NULL;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(stm32_dfsdm_release_buff_cb);
+
+static int stm32_dfsdm_audio_chan_init(struct iio_dev *indio_dev)
+{
+	struct iio_chan_spec *ch;
+	struct stm32_dfsdm_audio *pdmc = iio_priv(indio_dev);
+	int ret;
+
+	ch = devm_kzalloc(&indio_dev->dev, sizeof(*ch), GFP_KERNEL);
+	if (!ch)
+		return -ENOMEM;
+
+	ret = stm32_dfsdm_channel_parse_of(pdmc->dfsdm, indio_dev, ch, 0);
+	if (ret < 0)
+		return ret;
+
+	ch->type = IIO_VOLTAGE;
+	ch->indexed = 1;
+	ch->scan_index = 0;
+	ch->ext_info = dfsdm_adc_ext_info;
+
+	ch->scan_type.sign = 's';
+	ch->scan_type.realbits = 24;
+	ch->scan_type.storagebits = 32;
+
+	pdmc->ch_id = ch->channel;
+	ret = stm32_dfsdm_chan_configure(pdmc->dfsdm,
+					 &pdmc->dfsdm->ch_list[ch->channel]);
+
+	indio_dev->num_channels = 1;
+	indio_dev->channels = ch;
+
+	return ret;
+}
+
+static const struct of_device_id stm32_dfsdm_audio_match[] = {
+	{ .compatible = "st,stm32-dfsdm-audio"},
+	{}
+};
+
+static int stm32_dfsdm_audio_dma_request(struct iio_dev *indio_dev)
+{
+	struct stm32_dfsdm_audio *pdmc = iio_priv(indio_dev);
+	struct dma_slave_config config;
+	int ret;
+
+	pdmc->dma_chan = dma_request_slave_channel(&indio_dev->dev, "rx");
+	if (!pdmc->dma_chan)
+		return -EINVAL;
+
+	pdmc->rx_buf = dma_alloc_coherent(pdmc->dma_chan->device->dev,
+					 DFSDM_DMA_BUFFER_SIZE,
+					 &pdmc->dma_buf, GFP_KERNEL);
+	if (!pdmc->rx_buf) {
+		ret = -ENOMEM;
+		goto err_release;
+	}
+
+	/* Configure DMA channel to read data register */
+	memset(&config, 0, sizeof(config));
+	config.src_addr = (dma_addr_t)pdmc->dfsdm->phys_base;
+	config.src_addr += DFSDM_RDATAR(pdmc->fl_id);
+	config.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
+
+	ret = dmaengine_slave_config(pdmc->dma_chan, &config);
+	if (ret)
+		goto err_free;
+
+	return 0;
+
+err_free:
+	dma_free_coherent(pdmc->dma_chan->device->dev, DFSDM_DMA_BUFFER_SIZE,
+			  pdmc->rx_buf, pdmc->dma_buf);
+err_release:
+	dma_release_channel(pdmc->dma_chan);
+
+	return ret;
+}
+
+static int stm32_dfsdm_audio_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct stm32_dfsdm_audio *pdmc;
+	struct device_node *np = dev->of_node;
+	struct iio_dev *iio;
+	char *name;
+	int ret, irq, val;
+
+	iio = devm_iio_device_alloc(dev, sizeof(*pdmc));
+	if (IS_ERR(iio)) {
+		dev_err(dev, "%s: Failed to allocate IIO\n", __func__);
+		return PTR_ERR(iio);
+	}
+
+	pdmc = iio_priv(iio);
+	if (IS_ERR(pdmc)) {
+		dev_err(dev, "%s: Failed to allocate ADC\n", __func__);
+		return PTR_ERR(pdmc);
+	}
+	pdmc->dfsdm = dev_get_drvdata(dev->parent);
+
+	iio->name = np->name;
+	iio->dev.parent = dev;
+	iio->dev.of_node = np;
+	iio->info = &stm32_dfsdm_info_pdmc;
+	iio->modes = INDIO_DIRECT_MODE;
+
+	platform_set_drvdata(pdev, pdmc);
+
+	ret = of_property_read_u32(dev->of_node, "reg", &pdmc->fl_id);
+	if (ret != 0) {
+		dev_err(dev, "Missing reg property\n");
+		return -EINVAL;
+	}
+
+	name = kzalloc(sizeof("dfsdm-pdm0"), GFP_KERNEL);
+	if (!name)
+		return -ENOMEM;
+	snprintf(name, sizeof("dfsdm-pdm0"), "dfsdm-pdm%d", pdmc->fl_id);
+	iio->name = name;
+
+	/*
+	 * In a first step IRQs generated for channels are not treated.
+	 * So IRQ associated to filter instance 0 is dedicated to the Filter 0.
+	 */
+	irq = platform_get_irq(pdev, 0);
+	ret = devm_request_irq(dev, irq, stm32_dfsdm_irq,
+			       0, pdev->name, pdmc);
+	if (ret < 0) {
+		dev_err(dev, "Failed to request IRQ\n");
+		return ret;
+	}
+
+	ret = of_property_read_u32(dev->of_node, "st,filter-order", &val);
+	if (ret < 0) {
+		dev_err(dev, "Failed to set filter order\n");
+		return ret;
+	}
+	pdmc->dfsdm->fl_list[pdmc->fl_id].ford = val;
+
+	ret = of_property_read_u32(dev->of_node, "st,filter0-sync", &val);
+	if (!ret)
+		pdmc->dfsdm->fl_list[pdmc->fl_id].sync_mode = val;
+
+	ret = stm32_dfsdm_audio_chan_init(iio);
+	if (ret < 0)
+		return ret;
+
+	ret = stm32_dfsdm_audio_dma_request(iio);
+	if (ret) {
+		dev_err(&pdev->dev, "DMA request failed\n");
+		return ret;
+	}
+
+	iio->modes |= INDIO_BUFFER_SOFTWARE;
+
+	ret = iio_triggered_buffer_setup(iio,
+					 &iio_pollfunc_store_time,
+					 &stm32_dfsdm_audio_trigger_handler,
+					 &stm32_dfsdm_buffer_setup_ops);
+	if (ret) {
+		dev_err(&pdev->dev, "Buffer setup failed\n");
+		goto err_dma_disable;
+	}
+
+	ret = iio_device_register(iio);
+	if (ret) {
+		dev_err(&pdev->dev, "IIO dev register failed\n");
+		goto err_buffer_cleanup;
+	}
+
+	return 0;
+
+err_buffer_cleanup:
+	iio_triggered_buffer_cleanup(iio);
+
+err_dma_disable:
+	if (pdmc->dma_chan) {
+		dma_free_coherent(pdmc->dma_chan->device->dev,
+				  DFSDM_DMA_BUFFER_SIZE,
+				  pdmc->rx_buf, pdmc->dma_buf);
+		dma_release_channel(pdmc->dma_chan);
+	}
+
+	return ret;
+}
+
+static int stm32_dfsdm_audio_remove(struct platform_device *pdev)
+{
+	struct stm32_dfsdm_audio *pdmc = platform_get_drvdata(pdev);
+	struct iio_dev *iio = iio_priv_to_dev(pdmc);
+
+	iio_device_unregister(iio);
+
+	return 0;
+}
+
+static struct platform_driver stm32_dfsdm_audio_driver = {
+	.driver = {
+		.name = "stm32-dfsdm-audio",
+		.of_match_table = stm32_dfsdm_audio_match,
+	},
+	.probe = stm32_dfsdm_audio_probe,
+	.remove = stm32_dfsdm_audio_remove,
+};
+module_platform_driver(stm32_dfsdm_audio_driver);
+
+MODULE_DESCRIPTION("STM32 sigma delta converter for PDM microphone");
+MODULE_AUTHOR("Arnaud Pouliquen <arnaud.pouliquen@st.com>");
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/iio/adc/stm32-dfsdm-audio.h b/include/linux/iio/adc/stm32-dfsdm-audio.h
new file mode 100644
index 0000000..9b41b28
--- /dev/null
+++ b/include/linux/iio/adc/stm32-dfsdm-audio.h
@@ -0,0 +1,41 @@
+/*
+ * This file discribe the STM32 DFSDM IIO driver API for audio part
+ *
+ * Copyright (C) 2017, STMicroelectronics - All Rights Reserved
+ * Author(s): Arnaud Pouliquen <arnaud.pouliquen@st.com>.
+ *
+ * License terms: GPL V2.0.
+ *
+ * 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.
+ */
+#ifndef STM32_DFSDM_AUDIO_H
+#define STM32_DFSDM_AUDIO_H
+
+/**
+ * stm32_dfsdm_get_buff_cb() - register callback for capture buffer period.
+ * @dev:	Pointer to client device.
+ * @indio_dev:	Device on which the channel exists.
+ * @cb:		Callback function.
+ *		@data:  pointer to data buffer
+ *		@size: size of the data buffer in bytes
+ * @private:	Private data passed to callback.
+ *
+ */
+int stm32_dfsdm_get_buff_cb(struct iio_dev *iio_dev,
+			    int (*cb)(const void *data, size_t size,
+				      void *private),
+			    void *private);
+/**
+ * stm32_dfsdm_get_buff_cb() - release callback for capture buffer period.
+ * @indio_dev:	Device on which the channel exists.
+ */
+int stm32_dfsdm_release_buff_cb(struct iio_dev *iio_dev);
+
+#endif
-- 
1.9.1
