linux-kernel - [PATCH v2 2/2] iio: adc: ti-ads8344: optimize consumption

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Date:   Thu, 16 Apr 2020 22:54:28 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Gregory CLEMENT <gregory.clement@...tlin.com>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Alexandre Belloni <alexandre.belloni@...tlin.com>
Subject: [PATCH v2 2/2] iio: adc: ti-ads8344: optimize consumption

Set the clock mode only once, at probe time and then keep the ADC powered
down between conversions.

Signed-off-by: Alexandre Belloni <alexandre.belloni@...tlin.com>
---
 drivers/iio/adc/ti-ads8344.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/adc/ti-ads8344.c b/drivers/iio/adc/ti-ads8344.c
index abe4b56c847c..40e7a9eee189 100644
--- a/drivers/iio/adc/ti-ads8344.c
+++ b/drivers/iio/adc/ti-ads8344.c
@@ -72,7 +72,7 @@ static const struct iio_chan_spec ads8344_channels[] = {
 };
 
 static int ads8344_adc_conversion(struct ads8344 *adc, int channel,
-				  bool differential)
+				  bool differential, u8 clock)
 {
 	struct spi_device *spi = adc->spi;
 	int ret;
@@ -81,7 +81,7 @@ static int ads8344_adc_conversion(struct ads8344 *adc, int channel,
 	if (!differential)
 		adc->tx_buf |= ADS8344_SINGLE_END;
 	adc->tx_buf |= ADS8344_CHANNEL(channel);
-	adc->tx_buf |= ADS8344_CLOCK_INTERNAL;
+	adc->tx_buf |= clock;
 
 	ret = spi_write(spi, &adc->tx_buf, 1);
 	if (ret)
@@ -106,7 +106,7 @@ static int ads8344_read_raw(struct iio_dev *iio,
 	case IIO_CHAN_INFO_RAW:
 		mutex_lock(&adc->lock);
 		*value = ads8344_adc_conversion(adc, channel->scan_index,
-						channel->differential);
+						channel->differential, 0);
 		mutex_unlock(&adc->lock);
 		if (*value < 0)
 			return *value;
@@ -161,6 +161,11 @@ static int ads8344_probe(struct spi_device *spi)
 	if (ret)
 		return ret;
 
+	/* Do a dummy read and set external clock mode */
+	ret = ads8344_adc_conversion(adc, 0, 0, ADS8344_CLOCK_INTERNAL);
+	if (ret < 0)
+		return ret;
+
 	spi_set_drvdata(spi, indio_dev);
 
 	ret = iio_device_register(indio_dev);
-- 
2.25.2