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From:   Oleksij Rempel <o.rempel@pengutronix.de>
To:     Rob Herring <robh+dt@kernel.org>,
        Jonathan Cameron <jic23@kernel.org>
Cc:     Oleksij Rempel <o.rempel@pengutronix.de>,
        Andy Shevchenko <andy.shevchenko@gmail.com>,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        Pengutronix Kernel Team <kernel@pengutronix.de>,
        David Jander <david@protonic.nl>,
        Robin van der Gracht <robin@protonic.nl>,
        linux-iio@vger.kernel.org, Lars-Peter Clausen <lars@metafoo.de>,
        Peter Meerwald-Stadler <pmeerw@pmeerw.net>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>
Subject: [PATCH v6 3/3] iio: adc: add ADC driver for the TI TSC2046 controller
Date:   Wed, 28 Apr 2021 09:32:08 +0200
Message-Id: <20210428073208.19570-4-o.rempel@pengutronix.de>
In-Reply-To: <20210428073208.19570-1-o.rempel@pengutronix.de>
References: <20210428073208.19570-1-o.rempel@pengutronix.de>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Basically the TI TSC2046 touchscreen controller is 8 channel ADC optimized for
the touchscreen use case. By implementing it as an IIO ADC device, we can
make use of resistive-adc-touch and iio-hwmon drivers.

Polled readings are currently not implemented to keep this patch small, so
iio-hwmon will not work out of the box for now.

So far, this driver was tested with a custom version of resistive-adc-touch driver,
since it needs to be extended to make use of Z1 and Z2 channels. The X/Y
are working without additional changes.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
---
 MAINTAINERS                  |   8 +
 drivers/iio/adc/Kconfig      |  12 +
 drivers/iio/adc/Makefile     |   1 +
 drivers/iio/adc/ti-tsc2046.c | 720 +++++++++++++++++++++++++++++++++++
 4 files changed, 741 insertions(+)
 create mode 100644 drivers/iio/adc/ti-tsc2046.c

diff --git a/MAINTAINERS b/MAINTAINERS
index ccc59fd7e5c0..861904555c17 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -18009,6 +18009,14 @@ S:	Supported
 F:	Documentation/devicetree/bindings/net/nfc/trf7970a.txt
 F:	drivers/nfc/trf7970a.c
 
+TI TSC2046 ADC DRIVER
+M:	Oleksij Rempel <o.rempel@pengutronix.de>
+R:	kernel@pengutronix.de
+L:	linux-iio@vger.kernel.org
+S:	Maintained
+F:	Documentation/devicetree/bindings/iio/adc/ti,tsc2046.yaml
+F:	drivers/iio/adc/ti-tsc2046.c
+
 TI TWL4030 SERIES SOC CODEC DRIVER
 M:	Peter Ujfalusi <peter.ujfalusi@gmail.com>
 L:	alsa-devel@alsa-project.org (moderated for non-subscribers)
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index c7946c439612..db0c8fb60515 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -1190,6 +1190,18 @@ config TI_TLC4541
 	  This driver can also be built as a module. If so, the module will be
 	  called ti-tlc4541.
 
+config TI_TSC2046
+	tristate "Texas Instruments TSC2046 ADC driver"
+	depends on SPI
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
+	help
+	  Say yes here to build support for ADC functionality of Texas
+	  Instruments TSC2046 touch screen controller.
+
+	  This driver can also be built as a module. If so, the module will be
+	  called ti-tsc2046.
+
 config TWL4030_MADC
 	tristate "TWL4030 MADC (Monitoring A/D Converter)"
 	depends on TWL4030_CORE
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index a226657d19c0..f70d877c555a 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -106,6 +106,7 @@ obj-$(CONFIG_TI_ADS124S08) += ti-ads124s08.o
 obj-$(CONFIG_TI_ADS131E08) += ti-ads131e08.o
 obj-$(CONFIG_TI_AM335X_ADC) += ti_am335x_adc.o
 obj-$(CONFIG_TI_TLC4541) += ti-tlc4541.o
+obj-$(CONFIG_TI_TSC2046) += ti-tsc2046.o
 obj-$(CONFIG_TWL4030_MADC) += twl4030-madc.o
 obj-$(CONFIG_TWL6030_GPADC) += twl6030-gpadc.o
 obj-$(CONFIG_VF610_ADC) += vf610_adc.o
diff --git a/drivers/iio/adc/ti-tsc2046.c b/drivers/iio/adc/ti-tsc2046.c
new file mode 100644
index 000000000000..b86a3156f159
--- /dev/null
+++ b/drivers/iio/adc/ti-tsc2046.c
@@ -0,0 +1,720 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Texas Instruments TSC2046 SPI ADC driver
+ *
+ * Copyright (c) 2021 Oleksij Rempel <kernel@pengutronix.de>, Pengutronix
+ */
+
+#include <linux/bitfield.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/spi/spi.h>
+
+#include <asm/unaligned.h>
+
+#include <linux/iio/buffer.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
+#include <linux/iio/trigger.h>
+
+/*
+ * The PENIRQ of TSC2046 controller is implemented as level shifter attached to
+ * the X+ line. If voltage of the X+ line reaches a specific level the IRQ will
+ * be activated or deactivated.
+ * To make this kind of IRQ reusable as trigger following additions were
+ * implemented:
+ * - rate limiting:
+ *   For typical touchscreen use case, we need to trigger about each 10ms.
+ * - hrtimer:
+ *   Continue triggering at least once after the IRQ was deactivated. Then
+ *   deactivate this trigger to stop sampling in order to reduce power
+ *   consumption.
+ */
+
+#define TI_TSC2046_NAME				"tsc2046"
+
+/* This driver doesn't aim at the peak continuous sample rate */
+#define	TI_TSC2046_MAX_SAMPLE_RATE		125000
+#define	TI_TSC2046_SAMPLE_BITS \
+	BITS_PER_TYPE(struct tsc2046_adc_atom)
+#define	TI_TSC2046_MAX_CLK_FREQ \
+	(TI_TSC2046_MAX_SAMPLE_RATE * TI_TSC2046_SAMPLE_BITS)
+
+#define TI_TSC2046_SAMPLE_INTERVAL_US		10000
+
+#define TI_TSC2046_START			BIT(7)
+#define TI_TSC2046_ADDR				GENMASK(6, 4)
+#define TI_TSC2046_ADDR_TEMP1			7
+#define TI_TSC2046_ADDR_AUX			6
+#define TI_TSC2046_ADDR_X			5
+#define TI_TSC2046_ADDR_Z2			4
+#define TI_TSC2046_ADDR_Z1			3
+#define TI_TSC2046_ADDR_VBAT			2
+#define TI_TSC2046_ADDR_Y			1
+#define TI_TSC2046_ADDR_TEMP0			0
+
+/*
+ * The mode bit sets the resolution of the ADC. With this bit low, the next
+ * conversion has 12-bit resolution, whereas with this bit high, the next
+ * conversion has 8-bit resolution. This driver is optimized for 12-bit mode.
+ * So, for this driver, this bit should stay zero.
+ */
+#define TI_TSC2046_8BIT_MODE			BIT(3)
+
+/*
+ * SER/DFR - The SER/DFR bit controls the reference mode, either single-ended
+ * (high) or differential (low).
+ */
+#define TI_TSC2046_SER				BIT(2)
+
+/*
+ * If VREF_ON and ADC_ON are both zero, then the chip operates in
+ * auto-wake/suspend mode. In most case this bits should stay zero.
+ */
+#define TI_TSC2046_PD1_VREF_ON			BIT(1)
+#define TI_TSC2046_PD0_ADC_ON			BIT(0)
+
+/*
+ * All supported devices can do 8 or 12bit resolution. This driver
+ * supports only 12bit mode, here we have a 16bit data transfer, where
+ * the MSB and the 3 LSB are 0.
+ */
+#define TI_TSC2046_DATA_12BIT			GENMASK(14, 3)
+
+#define TI_TSC2046_MAX_CHAN			8
+
+/* Represents a HW sample */
+struct tsc2046_adc_atom {
+	/*
+	 * Command transmitted to the controller. This field is empty on the RX
+	 * buffer.
+	 */
+	u8 cmd;
+	/*
+	 * Data received from the controller. This field is empty for the TX
+	 * buffer
+	 */
+	__be16 data;
+} __packed;
+
+/* Layout of atomic buffers within big buffer */
+struct tsc2046_adc_group_layout {
+	/* Group offset within the SPI RX buffer */
+	unsigned int offset;
+	/*
+	 * Amount of tsc2046_adc_atom structs within the same command gathered
+	 * within same group.
+	 */
+	unsigned int count;
+	/*
+	 * Settling samples (tsc2046_adc_atom structs) which should be skipped
+	 * before good samples will start.
+	 */
+	unsigned int skip;
+};
+
+struct tsc2046_adc_dcfg {
+	const struct iio_chan_spec *channels;
+	unsigned int num_channels;
+};
+
+struct tsc2046_adc_ch_cfg {
+	unsigned int settling_time_us;
+	unsigned int oversampling_ratio;
+};
+
+struct tsc2046_adc_priv {
+	struct spi_device *spi;
+	const struct tsc2046_adc_dcfg *dcfg;
+
+	struct iio_trigger *trig;
+	struct hrtimer trig_timer;
+	spinlock_t trig_lock;
+	unsigned int trig_more_count;
+
+	struct spi_transfer xfer;
+	struct spi_message msg;
+
+	struct {
+		/* Scan data for each channel */
+		u16 data[TI_TSC2046_MAX_CHAN];
+		/* Timestamp */
+		s64 ts __aligned(8);
+	} scan_buf;
+
+	/*
+	 * Lock to protect the layout and the SPI transfer buffer.
+	 * tsc2046_adc_group_layout can be changed within update_scan_mode(),
+	 * in this case the l[] and tx/rx buffer will be out of sync to each
+	 * other.
+	 */
+	struct mutex slock;
+	struct tsc2046_adc_group_layout l[TI_TSC2046_MAX_CHAN];
+	struct tsc2046_adc_atom *rx;
+	struct tsc2046_adc_atom *tx;
+
+	struct tsc2046_adc_atom *rx_one;
+	struct tsc2046_adc_atom *tx_one;
+
+	unsigned int count;
+	unsigned int groups;
+	u32 effective_speed_hz;
+	u32 scan_interval_us;
+	u32 time_per_scan_us;
+	u32 time_per_bit_ns;
+
+	struct tsc2046_adc_ch_cfg ch_cfg[TI_TSC2046_MAX_CHAN];
+};
+
+#define TI_TSC2046_V_CHAN(index, bits, name)			\
+{								\
+	.type = IIO_VOLTAGE,					\
+	.indexed = 1,						\
+	.channel = index,					\
+	.datasheet_name = "#name",				\
+	.scan_index = index,					\
+	.scan_type = {						\
+		.sign = 'u',					\
+		.realbits = bits,				\
+		.storagebits = 16,				\
+		.endianness = IIO_CPU,				\
+	},							\
+}
+
+#define DECLARE_TI_TSC2046_8_CHANNELS(name, bits) \
+const struct iio_chan_spec name ## _channels[] = { \
+	TI_TSC2046_V_CHAN(0, bits, TEMP0), \
+	TI_TSC2046_V_CHAN(1, bits, Y), \
+	TI_TSC2046_V_CHAN(2, bits, VBAT), \
+	TI_TSC2046_V_CHAN(3, bits, Z1), \
+	TI_TSC2046_V_CHAN(4, bits, Z2), \
+	TI_TSC2046_V_CHAN(5, bits, X), \
+	TI_TSC2046_V_CHAN(6, bits, AUX), \
+	TI_TSC2046_V_CHAN(7, bits, TEMP1), \
+	IIO_CHAN_SOFT_TIMESTAMP(8), \
+}
+
+static DECLARE_TI_TSC2046_8_CHANNELS(tsc2046_adc, 12);
+
+static const struct tsc2046_adc_dcfg tsc2046_adc_dcfg_tsc2046e = {
+	.channels = tsc2046_adc_channels,
+	.num_channels = ARRAY_SIZE(tsc2046_adc_channels),
+};
+
+/*
+ * Convert time to a number of samples which can be transferred within this
+ * time.
+ */
+static unsigned int tsc2046_adc_time_to_count(struct tsc2046_adc_priv *priv,
+					      unsigned long time)
+{
+	unsigned int bit_count, sample_count;
+
+	bit_count = DIV_ROUND_UP(time * NSEC_PER_USEC, priv->time_per_bit_ns);
+	sample_count = DIV_ROUND_UP(bit_count, TI_TSC2046_SAMPLE_BITS);
+
+	dev_dbg(&priv->spi->dev, "Effective speed %u, time per bit: %u, count bits: %u, count samples: %u\n",
+		priv->effective_speed_hz, priv->time_per_bit_ns,
+		bit_count, sample_count);
+
+	return sample_count;
+}
+
+static u8 tsc2046_adc_get_cmd(struct tsc2046_adc_priv *priv, int ch_idx,
+			      bool keep_power)
+{
+	u32 pd;
+
+	/*
+	 * if PD bits are 0, controller will automatically disable ADC, VREF and
+	 * enable IRQ.
+	 */
+	if (keep_power)
+		pd = TI_TSC2046_PD0_ADC_ON;
+	else
+		pd = 0;
+
+	return TI_TSC2046_START | FIELD_PREP(TI_TSC2046_ADDR, ch_idx) | pd;
+}
+
+static u16 tsc2046_adc_get_value(struct tsc2046_adc_atom *buf)
+{
+	return FIELD_GET(TI_TSC2046_DATA_12BIT, get_unaligned_be16(&buf->data));
+}
+
+static int tsc2046_adc_read_one(struct tsc2046_adc_priv *priv, int ch_idx,
+				u32 *effective_speed_hz)
+{
+	struct spi_transfer xfer;
+	struct spi_message msg;
+	int ret;
+
+	memset(&xfer, 0, sizeof(xfer));
+	priv->tx_one->cmd = tsc2046_adc_get_cmd(priv, ch_idx, false);
+	priv->tx_one->data = 0;
+	xfer.tx_buf = priv->tx_one;
+	xfer.rx_buf = priv->rx_one;
+	xfer.len = sizeof(*priv->tx_one);
+	spi_message_init(&msg);
+	spi_message_add_tail(&xfer, &msg);
+
+	/*
+	 * We aren't using spi_write_then_read() because we need to be able
+	 * to get hold of the effective_speed_hz from the xfer
+	 */
+	ret = spi_sync(priv->spi, &msg);
+	if (ret) {
+		dev_err_ratelimited(&priv->spi->dev, "SPI transfer failed %pe\n",
+				    ERR_PTR(ret));
+		return ret;
+	}
+
+	if (effective_speed_hz)
+		*effective_speed_hz = xfer.effective_speed_hz;
+
+	return tsc2046_adc_get_value(priv->rx_one);
+}
+
+static size_t tsc2046_adc_group_set_layout(struct tsc2046_adc_priv *priv,
+					   unsigned int group,
+					   unsigned int ch_idx)
+{
+	struct tsc2046_adc_ch_cfg *ch = &priv->ch_cfg[ch_idx];
+	struct tsc2046_adc_group_layout *cur;
+	unsigned int max_count, count_skip;
+	unsigned int offset = 0;
+
+	if (group)
+		offset = priv->l[group - 1].offset + priv->l[group - 1].count;
+
+	count_skip = tsc2046_adc_time_to_count(priv, ch->settling_time_us);
+	max_count = count_skip + ch->oversampling_ratio;
+
+	cur = &priv->l[group];
+	cur->offset = offset;
+	cur->count = max_count;
+	cur->skip = count_skip;
+
+	return sizeof(*priv->tx) * max_count;
+}
+
+static void tsc2046_adc_group_set_cmd(struct tsc2046_adc_priv *priv,
+				      unsigned int group, int ch_idx)
+{
+	struct tsc2046_adc_group_layout *l = &priv->l[group];
+	unsigned int i;
+	u8 cmd;
+
+	/*
+	 * Do not enable automatic power down on working samples. Otherwise the
+	 * plates will never be completely charged.
+	 */
+	cmd = tsc2046_adc_get_cmd(priv, ch_idx, true);
+
+	for (i = 0; i < l->count - 1; i++)
+		priv->tx[l->offset + i].cmd = cmd;
+
+	/* automatically power down on last sample */
+	priv->tx[l->offset + i].cmd = tsc2046_adc_get_cmd(priv, ch_idx, false);
+}
+
+static u16 tsc2046_adc_get_val(struct tsc2046_adc_priv *priv, int group)
+{
+	struct tsc2046_adc_group_layout *l;
+	unsigned int val, val_normalized = 0;
+	int valid_count, i;
+
+	l = &priv->l[group];
+	valid_count = l->count - l->skip;
+
+	for (i = 0; i < valid_count; i++) {
+		val = tsc2046_adc_get_value(&priv->rx[l->offset + l->skip + i]);
+		val_normalized += val;
+	}
+
+	return DIV_ROUND_UP(val_normalized, valid_count);
+}
+
+static int tsc2046_adc_scan(struct iio_dev *indio_dev)
+{
+	struct tsc2046_adc_priv *priv = iio_priv(indio_dev);
+	struct device *dev = &priv->spi->dev;
+	int group;
+	int ret;
+
+	ret = spi_sync(priv->spi, &priv->msg);
+	if (ret < 0) {
+		dev_err_ratelimited(dev, "SPI transfer failed: %pe\n", ERR_PTR(ret));
+		return ret;
+	}
+
+	for (group = 0; group < priv->groups; group++)
+		priv->scan_buf.data[group] = tsc2046_adc_get_val(priv, group);
+
+	ret = iio_push_to_buffers_with_timestamp(indio_dev, &priv->scan_buf,
+						 iio_get_time_ns(indio_dev));
+	/* If the consumer is kfifo, we may get a EBUSY here - ignore it. */
+	if (ret < 0 && ret != -EBUSY) {
+		dev_err_ratelimited(dev, "Failed to push scan buffer %pe\n",
+				    ERR_PTR(ret));
+
+		return ret;
+	}
+
+	return 0;
+}
+
+static irqreturn_t tsc2046_adc_trigger_handler(int irq, void *p)
+{
+	struct iio_poll_func *pf = p;
+	struct iio_dev *indio_dev = pf->indio_dev;
+	struct tsc2046_adc_priv *priv = iio_priv(indio_dev);
+
+	mutex_lock(&priv->slock);
+	tsc2046_adc_scan(indio_dev);
+	mutex_unlock(&priv->slock);
+
+	iio_trigger_notify_done(indio_dev->trig);
+
+	return IRQ_HANDLED;
+}
+
+static int tsc2046_adc_update_scan_mode(struct iio_dev *indio_dev,
+					const unsigned long *active_scan_mask)
+{
+	struct tsc2046_adc_priv *priv = iio_priv(indio_dev);
+	unsigned int ch_idx, group = 0;
+	size_t size;
+
+	mutex_lock(&priv->slock);
+
+	size = 0;
+	for_each_set_bit(ch_idx, active_scan_mask, indio_dev->num_channels) {
+		size += tsc2046_adc_group_set_layout(priv, group, ch_idx);
+		tsc2046_adc_group_set_cmd(priv, group, ch_idx);
+		group++;
+	}
+
+	priv->groups = group;
+	priv->xfer.len = size;
+	priv->time_per_scan_us = size * 8 * priv->time_per_bit_ns / NSEC_PER_USEC;
+
+	if ((priv->scan_interval_us - priv->time_per_scan_us) < 0)
+		dev_warn(&priv->spi->dev, "The scan interval (%d) is less then calculated scan time (%d)\n",
+			 priv->scan_interval_us, priv->time_per_scan_us);
+
+	mutex_unlock(&priv->slock);
+
+	return 0;
+}
+
+static const struct iio_info tsc2046_adc_info = {
+	.update_scan_mode = tsc2046_adc_update_scan_mode,
+};
+
+static enum hrtimer_restart tsc2046_adc_trig_more(struct hrtimer *hrtimer)
+{
+	struct tsc2046_adc_priv *priv = container_of(hrtimer,
+						     struct tsc2046_adc_priv,
+						     trig_timer);
+	unsigned long flags;
+
+	spin_lock_irqsave(&priv->trig_lock, flags);
+
+	disable_irq_nosync(priv->spi->irq);
+
+	priv->trig_more_count++;
+	iio_trigger_poll(priv->trig);
+
+	spin_unlock_irqrestore(&priv->trig_lock, flags);
+
+	return HRTIMER_NORESTART;
+}
+
+static irqreturn_t tsc2046_adc_irq(int irq, void *dev_id)
+{
+	struct iio_dev *indio_dev = dev_id;
+	struct tsc2046_adc_priv *priv = iio_priv(indio_dev);
+
+	spin_lock(&priv->trig_lock);
+
+	hrtimer_try_to_cancel(&priv->trig_timer);
+
+	priv->trig_more_count = 0;
+	disable_irq_nosync(priv->spi->irq);
+	iio_trigger_poll(priv->trig);
+
+	spin_unlock(&priv->trig_lock);
+
+	return IRQ_HANDLED;
+}
+
+static void tsc2046_adc_reenable_trigger(struct iio_trigger *trig)
+{
+	struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
+	struct tsc2046_adc_priv *priv = iio_priv(indio_dev);
+	unsigned long flags;
+	int delta;
+
+	/*
+	 * We can sample it as fast as we can, but usually we do not need so
+	 * many samples. Reduce the sample rate for default (touchscreen) use
+	 * case.
+	 * Currently we do not need a highly precise sample rate. It is enough
+	 * to have calculated numbers.
+	 */
+	delta = priv->scan_interval_us - priv->time_per_scan_us;
+	if (delta > 0)
+		fsleep(delta);
+
+	spin_lock_irqsave(&priv->trig_lock, flags);
+
+	/*
+	 * We need to trigger at least one extra sample to detect state
+	 * difference on ADC side.
+	 */
+	if (!priv->trig_more_count) {
+		int timeout_ms = DIV_ROUND_UP(priv->scan_interval_us,
+					      USEC_PER_MSEC);
+
+		hrtimer_start(&priv->trig_timer, ms_to_ktime(timeout_ms),
+			      HRTIMER_MODE_REL_SOFT);
+	}
+
+	enable_irq(priv->spi->irq);
+
+	spin_unlock_irqrestore(&priv->trig_lock, flags);
+}
+
+static int tsc2046_adc_set_trigger_state(struct iio_trigger *trig, bool enable)
+{
+	struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
+	struct tsc2046_adc_priv *priv = iio_priv(indio_dev);
+
+	if (enable) {
+		enable_irq(priv->spi->irq);
+	} else {
+		disable_irq(priv->spi->irq);
+		hrtimer_try_to_cancel(&priv->trig_timer);
+	}
+
+	return 0;
+}
+
+static const struct iio_trigger_ops tsc2046_adc_trigger_ops = {
+	.set_trigger_state = tsc2046_adc_set_trigger_state,
+	.reenable = tsc2046_adc_reenable_trigger,
+};
+
+static int tsc2046_adc_setup_spi_msg(struct tsc2046_adc_priv *priv)
+{
+	unsigned int ch_idx;
+	size_t size;
+	int ret;
+
+	priv->tx_one = devm_kzalloc(&priv->spi->dev, sizeof(*priv->tx_one),
+				    GFP_KERNEL);
+	if (!priv->tx_one)
+		return -ENOMEM;
+
+	priv->rx_one = devm_kzalloc(&priv->spi->dev, sizeof(*priv->rx_one),
+				    GFP_KERNEL);
+	if (!priv->rx_one)
+		return -ENOMEM;
+
+	/*
+	 * Make dummy read to set initial power state and get real SPI clock
+	 * freq. It seems to be not important which channel is used for this
+	 * case.
+	 */
+	ret = tsc2046_adc_read_one(priv, TI_TSC2046_ADDR_TEMP0,
+				   &priv->effective_speed_hz);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * In case SPI controller do not report effective_speed_hz, use
+	 * configure value and hope it will match.
+	 */
+	if (!priv->effective_speed_hz)
+		priv->effective_speed_hz = priv->spi->max_speed_hz;
+
+
+	priv->scan_interval_us = TI_TSC2046_SAMPLE_INTERVAL_US;
+	priv->time_per_bit_ns = DIV_ROUND_UP(NSEC_PER_SEC,
+					     priv->effective_speed_hz);
+
+	/*
+	 * Calculate and allocate maximal size buffer if all channels are
+	 * enabled.
+	 */
+	size = 0;
+	for (ch_idx = 0; ch_idx < priv->dcfg->num_channels; ch_idx++)
+		size += tsc2046_adc_group_set_layout(priv, ch_idx, ch_idx);
+
+	priv->tx = devm_kzalloc(&priv->spi->dev, size, GFP_KERNEL);
+	if (!priv->tx)
+		return -ENOMEM;
+
+	priv->rx = devm_kzalloc(&priv->spi->dev, size, GFP_KERNEL);
+	if (!priv->rx)
+		return -ENOMEM;
+
+	spi_message_init(&priv->msg);
+	priv->msg.context = priv;
+
+	priv->xfer.tx_buf = priv->tx;
+	priv->xfer.rx_buf = priv->rx;
+	priv->xfer.len = size;
+	spi_message_add_tail(&priv->xfer, &priv->msg);
+
+	return 0;
+}
+
+static void tsc2046_adc_parse_fwnode(struct tsc2046_adc_priv *priv)
+{
+	struct fwnode_handle *child;
+	struct device *dev = &priv->spi->dev;
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(priv->ch_cfg); i++) {
+		priv->ch_cfg[i].settling_time_us = 1;
+		priv->ch_cfg[i].oversampling_ratio = 1;
+	}
+
+	device_for_each_child_node(dev, child) {
+		u32 stl, overs, reg;
+		int ret;
+
+		ret = fwnode_property_read_u32(child, "reg", &reg);
+		if (ret) {
+			dev_err(dev, "invalid reg on %pfw, err: %pe\n", child,
+				ERR_PTR(ret));
+			continue;
+		}
+
+		if (reg >= ARRAY_SIZE(priv->ch_cfg)) {
+			dev_err(dev, "%pfw: Unsupported reg value: %i, max supported is: %zu.\n",
+				child, reg, ARRAY_SIZE(priv->ch_cfg));
+			continue;
+		}
+
+		ret = fwnode_property_read_u32(child, "settling-time-us", &stl);
+		if (!ret)
+			priv->ch_cfg[reg].settling_time_us = stl;
+
+		ret = fwnode_property_read_u32(child, "oversampling-ratio",
+					       &overs);
+		if (!ret)
+			priv->ch_cfg[reg].oversampling_ratio = overs;
+	}
+}
+
+static int tsc2046_adc_probe(struct spi_device *spi)
+{
+	const struct tsc2046_adc_dcfg *dcfg;
+	struct device *dev = &spi->dev;
+	struct tsc2046_adc_priv *priv;
+	struct iio_dev *indio_dev;
+	struct iio_trigger *trig;
+	int ret;
+
+	if (spi->max_speed_hz > TI_TSC2046_MAX_CLK_FREQ) {
+		dev_err(dev, "SPI max_speed_hz is too high: %d Hz. Max supported freq is %zu Hz\n",
+			spi->max_speed_hz, TI_TSC2046_MAX_CLK_FREQ);
+		return -EINVAL;
+	}
+
+	dcfg = device_get_match_data(dev);
+	if (!dcfg)
+		return -EINVAL;
+
+	spi->bits_per_word = 8;
+	spi->mode &= ~SPI_MODE_X_MASK;
+	spi->mode |= SPI_MODE_0;
+	ret = spi_setup(spi);
+	if (ret < 0)
+		return dev_err_probe(dev, ret, "Error in SPI setup\n");
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*priv));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	priv = iio_priv(indio_dev);
+	priv->dcfg = dcfg;
+
+	spi_set_drvdata(spi, indio_dev);
+
+	priv->spi = spi;
+
+	indio_dev->name = TI_TSC2046_NAME;
+	indio_dev->modes = INDIO_DIRECT_MODE | INDIO_BUFFER_TRIGGERED;
+	indio_dev->channels = dcfg->channels;
+	indio_dev->num_channels = dcfg->num_channels;
+	indio_dev->info = &tsc2046_adc_info;
+
+	tsc2046_adc_parse_fwnode(priv);
+
+	ret = tsc2046_adc_setup_spi_msg(priv);
+	if (ret)
+		return ret;
+
+	mutex_init(&priv->slock);
+
+	/* TODO: remove IRQ_NOAUTOEN after needed patches are mainline */
+	irq_set_status_flags(spi->irq, IRQ_NOAUTOEN);
+	ret = devm_request_irq(dev, spi->irq, &tsc2046_adc_irq,
+			       0, indio_dev->name, indio_dev);
+	if (ret)
+		return ret;
+
+	trig = devm_iio_trigger_alloc(dev, "touchscreen-%s", indio_dev->name);
+	if (!trig)
+		return -ENOMEM;
+
+	priv->trig = trig;
+	iio_trigger_set_drvdata(trig, indio_dev);
+	trig->ops = &tsc2046_adc_trigger_ops;
+
+	spin_lock_init(&priv->trig_lock);
+	hrtimer_init(&priv->trig_timer, CLOCK_MONOTONIC,
+		     HRTIMER_MODE_REL_SOFT);
+	priv->trig_timer.function = tsc2046_adc_trig_more;
+
+	ret = devm_iio_trigger_register(dev, trig);
+	if (ret) {
+		dev_err(dev, "failed to register trigger\n");
+		return ret;
+	}
+
+	ret = devm_iio_triggered_buffer_setup(dev, indio_dev, NULL,
+					      &tsc2046_adc_trigger_handler, NULL);
+	if (ret) {
+		dev_err(dev, "Failed to setup triggered buffer\n");
+		return ret;
+	}
+
+	/* set default trigger */
+	indio_dev->trig = iio_trigger_get(priv->trig);
+
+	return devm_iio_device_register(dev, indio_dev);
+}
+
+static const struct of_device_id ads7950_of_table[] = {
+	{ .compatible = "ti,tsc2046e-adc", .data = &tsc2046_adc_dcfg_tsc2046e },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ads7950_of_table);
+
+static struct spi_driver tsc2046_adc_driver = {
+	.driver = {
+		.name = "tsc2046",
+		.of_match_table = ads7950_of_table,
+	},
+	.probe = tsc2046_adc_probe,
+};
+module_spi_driver(tsc2046_adc_driver);
+
+MODULE_AUTHOR("Oleksij Rempel <kernel@pengutronix.de>");
+MODULE_DESCRIPTION("TI TSC2046 ADC");
+MODULE_LICENSE("GPL v2");
-- 
2.29.2