iio: adc: mcp3911: add support for interrupts

Make it possible to read values upon interrupts.
Configure Data Ready Signal Output Pin to either HiZ or push-pull and
use it as interrupt source.
Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20220815061625.35568-7-marcus.folkesson@gmail.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/mcp3911.c

@@ -31,6 +31,7 @@
 #define MCP3911_REG_GAIN		0x09
 
 #define MCP3911_REG_STATUSCOM		0x0a
+#define MCP3911_STATUSCOM_DRHIZ         BIT(12)
 #define MCP3911_STATUSCOM_READ		GENMASK(7, 6)
 #define MCP3911_STATUSCOM_CH1_24WIDTH	BIT(4)
 #define MCP3911_STATUSCOM_CH0_24WIDTH	BIT(3)
@@ -64,6 +65,7 @@ struct mcp3911 {
 	struct regulator *vref;
 	struct clk *clki;
 	u32 dev_addr;
+	struct iio_trigger *trig;
 	struct {
 		u32 channels[MCP3911_NUM_CHANNELS];
 		s64 ts __aligned(8);
@@ -344,6 +346,23 @@ static void mcp3911_cleanup_regulator(void *vref)
 	regulator_disable(vref);
 }
 
+static int mcp3911_set_trigger_state(struct iio_trigger *trig, bool enable)
+{
+	struct mcp3911 *adc = iio_trigger_get_drvdata(trig);
+
+	if (enable)
+		enable_irq(adc->spi->irq);
+	else
+		disable_irq(adc->spi->irq);
+
+	return 0;
+}
+
+static const struct iio_trigger_ops mcp3911_trigger_ops = {
+	.validate_device = iio_trigger_validate_own_device,
+	.set_trigger_state = mcp3911_set_trigger_state,
+};
+
 static int mcp3911_probe(struct spi_device *spi)
 {
 	struct iio_dev *indio_dev;
@@ -395,6 +414,15 @@ static int mcp3911_probe(struct spi_device *spi)
 	if (ret)
 		return ret;
 
+	if (device_property_read_bool(&adc->spi->dev, "microchip,data-ready-hiz"))
+		ret = mcp3911_update(adc, MCP3911_REG_STATUSCOM, MCP3911_STATUSCOM_DRHIZ,
+				0, 2);
+	else
+		ret = mcp3911_update(adc, MCP3911_REG_STATUSCOM, MCP3911_STATUSCOM_DRHIZ,
+				MCP3911_STATUSCOM_DRHIZ, 2);
+	if (ret)
+		return ret;
+
 	indio_dev->name = spi_get_device_id(spi)->name;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 	indio_dev->info = &mcp3911_info;
@@ -405,6 +433,31 @@ static int mcp3911_probe(struct spi_device *spi)
 
 	mutex_init(&adc->lock);
 
+	if (spi->irq > 0) {
+		adc->trig = devm_iio_trigger_alloc(&spi->dev, "%s-dev%d",
+				indio_dev->name,
+				iio_device_id(indio_dev));
+		if (!adc->trig)
+			return PTR_ERR(adc->trig);
+
+		adc->trig->ops = &mcp3911_trigger_ops;
+		iio_trigger_set_drvdata(adc->trig, adc);
+		ret = devm_iio_trigger_register(&spi->dev, adc->trig);
+		if (ret)
+			return ret;
+
+		/*
+		 * The device generates interrupts as long as it is powered up.
+		 * Some platforms might not allow the option to power it down so
+		 * don't enable the interrupt to avoid extra load on the system.
+		 */
+		ret = devm_request_irq(&spi->dev, spi->irq,
+				&iio_trigger_generic_data_rdy_poll, IRQF_NO_AUTOEN | IRQF_ONESHOT,
+				indio_dev->name, adc->trig);
+		if (ret)
+			return ret;
+	}
+
 	ret = devm_iio_triggered_buffer_setup(&spi->dev, indio_dev,
 			NULL,
 			mcp3911_trigger_handler, NULL);