iio: adc: ti-ads1015: fix incorrect data rate setting update

This change “iio: adc: ti-ads1015: fix incorrect data rate setting update” (commit 0d106b7) in Linux kernel is authored by Akinobu Mita <akinobu.mita [at] gmail.com> on Fri Jul 21 00:24:17 2017 +0900.

Description of "iio: adc: ti-ads1015: fix incorrect data rate setting update"

The change “iio: adc: ti-ads1015: fix incorrect data rate setting update” introduces changes as follows.

iio: adc: ti-ads1015: fix incorrect data rate setting update

The ti-ads1015 driver has eight iio voltage channels and each iio channel
can hold own sampling frequency information.

The ADS1015 device only have a single config register which contains an
input multiplexer selection, PGA and data rate settings.  So the driver
should load the correct settings when the input multiplexer selection is
changed.

However, regardless of which channlel is currently selected, changing any
iio channel's sampling frequency information immediately overwrites the
current data rate setting in the config register.

It breaks the current data rate setting if the different channel's sampling
frequency information is changed because the data rate setting is not
reloaded when the input multiplexer is switched.

This removes the unexpected config register update and correctly load the
data rate setting before getting adc result.

Cc: Daniel Baluta <daniel.baluta@gmail.com>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Linux kernel releases containing commit 0d106b7

The Linux kernel releases containing this commit are as follows.

Linux kernel code changes from "iio: adc: ti-ads1015: fix incorrect data rate setting update"

There are 27 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 drivers/iio/adc/ti-ads1015.c | 27 ++++++++++-----------------
 1 file changed, 10 insertions(+), 17 deletions(-)
 
diff --git a/drivers/iio/adc/ti-ads1015.c b/drivers/iio/adc/ti-ads1015.c
index 7972845b3823..897bc2f04ab6 100644
--- a/drivers/iio/adc/ti-ads1015.c
+++ b/drivers/iio/adc/ti-ads1015.c
@@ -252,9 +252,11 @@ int ads1015_get_adc_result(struct ads1015_data *data, int chan, int *val)
 
 	ret = regmap_update_bits_check(data->regmap, ADS1015_CFG_REG,
 				       ADS1015_CFG_MUX_MASK |
-				       ADS1015_CFG_PGA_MASK,
+				       ADS1015_CFG_PGA_MASK |
+				       ADS1015_CFG_DR_MASK,
 				       chan << ADS1015_CFG_MUX_SHIFT |
-				       pga << ADS1015_CFG_PGA_SHIFT,
+				       pga << ADS1015_CFG_PGA_SHIFT |
+				       dr << ADS1015_CFG_DR_SHIFT,
 				       &change);
 	if (ret < 0)
 		return ret;
@@ -325,25 +327,16 @@ static int ads1015_set_scale(struct ads1015_data *data, int chan,
 
 static int ads1015_set_data_rate(struct ads1015_data *data, int chan, int rate)
 {
-	int i, ret, rindex = -1;
+	int i;
 
-	for (i = 0; i < ARRAY_SIZE(ads1015_data_rate); i++)
+	for (i = 0; i < ARRAY_SIZE(ads1015_data_rate); i++) {
 		if (data->data_rate[i] == rate) {
-			rindex = i;
-			break;
+			data->channel_data[chan].data_rate = i;
+			return 0;
 		}
-	if (rindex < 0)
-		return -EINVAL;
-
-	ret = regmap_update_bits(data->regmap, ADS1015_CFG_REG,
-				 ADS1015_CFG_DR_MASK,
-				 rindex << ADS1015_CFG_DR_SHIFT);
-	if (ret < 0)
-		return ret;
-
-	data->channel_data[chan].data_rate = rindex;
+	}
 
-	return 0;
+	return -EINVAL;
 }
 
 static int ads1015_read_raw(struct iio_dev *indio_dev,

The commit for this change in Linux stable tree is 0d106b7 (patch).

Last modified: 2020/02/09