[PATCH v3 07/13] iio: adc: ad4134: Support buffered data read

[Marcelo Schmitt <marcelo.schmitt@analog.com>]

Enable users to run buffered data captures triggered by IIO trigger device.
Add an IIO timestamp channel so each data scan is provided with measurement
time information. Require single-read operations to be in IIO device direct
access mode to prevent buffered and single-shot data captures to disrupt
each other.

Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
---
Change log v2 -> v3:
- Now using IIO_DECLARE_BUFFER_WITH_TS macro to set properly sized triggered
  buffer storage that includes room for timestamp.

 drivers/iio/adc/Kconfig  |  2 ++
 drivers/iio/adc/ad4134.c | 61 +++++++++++++++++++++++++++++++++++++++-
 2 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index a802d8ee4dd9..fc7de0bb400a 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -125,6 +125,8 @@ config AD4134
 	depends on SPI
 	select REGMAP_SPI
 	select CRC8
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
 	help
 	  Say yes here to build support for Analog Devices AD4134 SPI analog to
 	  digital converters (ADC).
diff --git a/drivers/iio/adc/ad4134.c b/drivers/iio/adc/ad4134.c
index 14996a0d1fe8..f0196126515e 100644
--- a/drivers/iio/adc/ad4134.c
+++ b/drivers/iio/adc/ad4134.c
@@ -26,7 +26,10 @@
 #include <linux/unaligned.h>
 #include <linux/units.h>
 
+#include <linux/iio/buffer.h>
 #include <linux/iio/iio.h>
+#include <linux/iio/triggered_buffer.h>
+#include <linux/iio/trigger_consumer.h>
 
 #define AD4134_RESET_TIME_US			(10 * USEC_PER_SEC)
 
@@ -124,6 +127,13 @@ static const struct iio_chan_spec_ext_info ad4134_filter_type_ext_info[] = {
 	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),				\
 	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),			\
 	.ext_info = ad4134_filter_type_ext_info,				\
+	.scan_index = (_index),							\
+	.scan_type = {								\
+		.format = IIO_SCAN_FORMAT_SIGNED_INT,				\
+		.realbits = AD4134_CHAN_PRECISION_BITS,				\
+		.storagebits = 32,						\
+		.endianness = IIO_CPU,						\
+	},									\
 }
 
 static const struct iio_chan_spec ad4134_chan_set[] = {
@@ -131,6 +141,7 @@ static const struct iio_chan_spec ad4134_chan_set[] = {
 	AD4134_CHANNEL(1),
 	AD4134_CHANNEL(2),
 	AD4134_CHANNEL(3),
+	IIO_CHAN_SOFT_TIMESTAMP(4),
 };
 
 struct ad4134_state {
@@ -269,7 +280,7 @@ static int ad4134_data_read(struct ad4134_state *st, unsigned int reg,
 	 * interface. Now we read data from all channels but keep only the bits
 	 * from the requested one.
 	 */
-	for (i = 0; i < ARRAY_SIZE(ad4134_chan_set); i++) {
+	for (i = 0; i < AD4134_NUM_CHANNELS; i++) {
 		ret = spi_write_then_read(st->spi, NULL, 0, st->rx_buf,
 					  BITS_TO_BYTES(AD4134_CHAN_PRECISION_BITS));
 		if (ret)
@@ -333,6 +344,43 @@ static const struct regmap_config ad4134_regmap_config = {
 	.max_register = AD4134_CH_VREG(ARRAY_SIZE(ad4134_chan_set) - 1),
 };
 
+static irqreturn_t ad4134_trigger_handler(int irq, void *p)
+{
+	IIO_DECLARE_BUFFER_WITH_TS(u32, channels, AD4134_NUM_CHANNELS) = { };
+	struct iio_poll_func *pf = p;
+	struct iio_dev *indio_dev = pf->indio_dev;
+	struct ad4134_state *st = iio_priv(indio_dev);
+	struct spi_transfer xfer = {
+		.rx_buf = st->rx_buf,
+		.cs_off = true,
+		.len = BITS_TO_BYTES(AD4134_CHAN_PRECISION_BITS),
+	};
+	int ret;
+
+	gpiod_set_value_cansleep(st->odr_gpio, 1);
+	fsleep(1);
+	gpiod_set_value_cansleep(st->odr_gpio, 0);
+
+	/* Execute transfers for all channels so the entire data frame is read. */
+	for (int ch = 0, i = 0; ch < AD4134_NUM_CHANNELS; ch++) {
+		ret = spi_sync_transfer(st->spi, &xfer, 1);
+		if (ret)
+			goto out;
+
+		if (!test_bit(ch, indio_dev->active_scan_mask))
+			continue;
+
+		channels[i++] = get_unaligned_be24(st->rx_buf);
+	}
+
+	iio_push_to_buffers_with_ts(indio_dev, channels, sizeof(channels),
+				    pf->timestamp);
+
+out:
+	iio_trigger_notify_done(indio_dev->trig);
+	return IRQ_HANDLED;
+}
+
 static int ad4134_read_raw(struct iio_dev *indio_dev,
 			   struct iio_chan_spec const *chan,
 			   int *val, int *val2, long info)
@@ -342,6 +390,10 @@ static int ad4134_read_raw(struct iio_dev *indio_dev,
 
 	switch (info) {
 	case IIO_CHAN_INFO_RAW: {
+		IIO_DEV_ACQUIRE_DIRECT_MODE(indio_dev, claim);
+		if (IIO_DEV_ACQUIRE_FAILED(claim))
+			return -EBUSY;
+
 		guard(mutex)(&st->sync_lock);
 
 		gpiod_set_value_cansleep(st->odr_gpio, 1);
@@ -546,6 +598,13 @@ static int ad4134_probe(struct spi_device *spi)
 		return dev_err_probe(dev, ret,
 				     "failed to setup minimum I/O mode\n");
 
+	ret = devm_iio_triggered_buffer_setup(dev, indio_dev,
+					      iio_pollfunc_store_time,
+					      ad4134_trigger_handler,
+					      NULL);
+	if (ret)
+		return ret;
+
 	/* Bump precision to 24-bit */
 	ret = regmap_update_bits(st->regmap, AD4134_DATA_PACKET_CONFIG_REG,
 				 AD4134_DATA_PACKET_CONFIG_FRAME_MASK,
-- 
2.53.0