iio: hx711: add triggered buffer support

Add buffer to device data struct and add trigger function

Data format is quite simple:
      voltage - channel 0   32 Bit
      voltage - channel 1   32 Bit
      timestamp             64 Bit

Using both channels at the same time is working quite slow because of
changing the channel which needs a dummy read.

Signed-off-by: Andreas Klinger <ak@it-klinger.de>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/iio/adc/Kconfig

@@ -319,6 +319,8 @@ config HI8435
 config HX711
 	tristate "AVIA HX711 ADC for weight cells"
 	depends on GPIOLIB
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
 	help
 	  If you say yes here you get support for AVIA HX711 ADC which is used
 	  for weigh cells

drivers/iio/adc/hx711.c

@@ -24,6 +24,9 @@
 #include <linux/delay.h>
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
 #include <linux/gpio/consumer.h>
 #include <linux/regulator/consumer.h>
 
@@ -89,6 +92,11 @@ struct hx711_data {
 	int			gain_set;	/* gain set on device */
 	int			gain_chan_a;	/* gain for channel A */
 	struct mutex		lock;
+	/*
+	 * triggered buffer
+	 * 2x32-bit channel + 64-bit timestamp
+	 */
+	u32			buffer[4];
 };
 
 static int hx711_cycle(struct hx711_data *hx711_data)
@@ -236,34 +244,40 @@ static int hx711_set_gain_for_channel(struct hx711_data *hx711_data, int chan)
 	return 0;
 }
 
+static int hx711_reset_read(struct hx711_data *hx711_data, int chan)
+{
+	int ret;
+	int val;
+
+	/*
+	 * hx711_reset() must be called from here
+	 * because it could be calling hx711_read() by itself
+	 */
+	if (hx711_reset(hx711_data)) {
+		dev_err(hx711_data->dev, "reset failed!");
+		return -EIO;
+	}
+
+	ret = hx711_set_gain_for_channel(hx711_data, chan);
+	if (ret < 0)
+		return ret;
+
+	val = hx711_read(hx711_data);
+
+	return val;
+}
+
 static int hx711_read_raw(struct iio_dev *indio_dev,
 				const struct iio_chan_spec *chan,
 				int *val, int *val2, long mask)
 {
 	struct hx711_data *hx711_data = iio_priv(indio_dev);
-	int ret;
 
 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
 		mutex_lock(&hx711_data->lock);
 
-		/*
-		 * hx711_reset() must be called from here
-		 * because it could be calling hx711_read() by itself
-		 */
-		if (hx711_reset(hx711_data)) {
-			mutex_unlock(&hx711_data->lock);
-			dev_err(hx711_data->dev, "reset failed!");
-			return -EIO;
-		}
-
-		ret = hx711_set_gain_for_channel(hx711_data, chan->channel);
-		if (ret < 0) {
-			mutex_unlock(&hx711_data->lock);
-			return ret;
-		}
-
-		*val = hx711_read(hx711_data);
+		*val = hx711_reset_read(hx711_data, chan->channel);
 
 		mutex_unlock(&hx711_data->lock);
 
@@ -339,6 +353,36 @@ static int hx711_write_raw_get_fmt(struct iio_dev *indio_dev,
 	return IIO_VAL_INT_PLUS_NANO;
 }
 
+static irqreturn_t hx711_trigger(int irq, void *p)
+{
+	struct iio_poll_func *pf = p;
+	struct iio_dev *indio_dev = pf->indio_dev;
+	struct hx711_data *hx711_data = iio_priv(indio_dev);
+	int i, j = 0;
+
+	mutex_lock(&hx711_data->lock);
+
+	memset(hx711_data->buffer, 0, sizeof(hx711_data->buffer));
+
+	for (i = 0; i < indio_dev->masklength; i++) {
+		if (!test_bit(i, indio_dev->active_scan_mask))
+			continue;
+
+		hx711_data->buffer[j] = hx711_reset_read(hx711_data,
+					indio_dev->channels[i].channel);
+		j++;
+	}
+
+	iio_push_to_buffers_with_timestamp(indio_dev, hx711_data->buffer,
+							pf->timestamp);
+
+	mutex_unlock(&hx711_data->lock);
+
+	iio_trigger_notify_done(indio_dev->trig);
+
+	return IRQ_HANDLED;
+}
+
 static ssize_t hx711_scale_available_show(struct device *dev,
 				struct device_attribute *attr,
 				char *buf)
@@ -387,6 +431,13 @@ static const struct iio_chan_spec hx711_chan_spec[] = {
 		.indexed = 1,
 		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
 		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
+		.scan_index = 0,
+		.scan_type = {
+			.sign = 'u',
+			.realbits = 24,
+			.storagebits = 32,
+			.endianness = IIO_CPU,
+		},
 	},
 	{
 		.type = IIO_VOLTAGE,
@@ -394,7 +445,15 @@ static const struct iio_chan_spec hx711_chan_spec[] = {
 		.indexed = 1,
 		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
 		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
+		.scan_index = 1,
+		.scan_type = {
+			.sign = 'u',
+			.realbits = 24,
+			.storagebits = 32,
+			.endianness = IIO_CPU,
+		},
 	},
+	IIO_CHAN_SOFT_TIMESTAMP(2),
 };
 
 static int hx711_probe(struct platform_device *pdev)
@@ -459,10 +518,9 @@ static int hx711_probe(struct platform_device *pdev)
 	 * 1 LSB = (AVDD * 100) / GAIN / 1678 [10^-9 mV]
 	 */
 	ret = regulator_get_voltage(hx711_data->reg_avdd);
-	if (ret < 0) {
-		regulator_disable(hx711_data->reg_avdd);
-		return ret;
-	}
+	if (ret < 0)
+		goto error_regulator;
+
 	/* we need 10^-9 mV */
 	ret *= 100;
 
@@ -482,12 +540,27 @@ static int hx711_probe(struct platform_device *pdev)
 	indio_dev->channels = hx711_chan_spec;
 	indio_dev->num_channels = ARRAY_SIZE(hx711_chan_spec);
 
+	ret = iio_triggered_buffer_setup(indio_dev, iio_pollfunc_store_time,
+							hx711_trigger, NULL);
+	if (ret < 0) {
+		dev_err(dev, "setup of iio triggered buffer failed\n");
+		goto error_regulator;
+	}
+
 	ret = iio_device_register(indio_dev);
 	if (ret < 0) {
 		dev_err(dev, "Couldn't register the device\n");
-		regulator_disable(hx711_data->reg_avdd);
+		goto error_buffer;
 	}
 
+	return 0;
+
+error_buffer:
+	iio_triggered_buffer_cleanup(indio_dev);
+
+error_regulator:
+	regulator_disable(hx711_data->reg_avdd);
+
 	return ret;
 }
 
@@ -501,6 +574,8 @@ static int hx711_remove(struct platform_device *pdev)
 
 	iio_device_unregister(indio_dev);
 
+	iio_triggered_buffer_cleanup(indio_dev);
+
 	regulator_disable(hx711_data->reg_avdd);
 
 	return 0;