patch "iio: adc: ti-ads1015: add adequate wait time to get correct" added to staging-next

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    iio: adc: ti-ads1015: add adequate wait time to get correct

to my staging git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
in the staging-next branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will also be merged in the next major kernel release
during the merge window.

If you have any questions about this process, please let me know.


>From 4744d4e2afebf9644a439da9ca73d822fdd67bd9 Mon Sep 17 00:00:00 2001
From: Akinobu Mita <akinobu.mita@gmail.com>
Date: Fri, 21 Jul 2017 00:24:22 +0900
Subject: iio: adc: ti-ads1015: add adequate wait time to get correct
 conversion

This driver assumes that the device is operating in the continuous
conversion mode which performs the conversion continuously.  So this driver
inserts a wait time before reading the conversion register if the
configuration is changed from a previous request.

Currently, the wait time is only the period required for a single
conversion that is calculated as the reciprocal of the sampling frequency.
However we also need to wait for the the previous conversion to complete.
Otherwise we probably get the conversion result for the previous
configuration when the sampling frequency is lower.

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>
---
 drivers/iio/adc/ti-ads1015.c | 31 +++++++++++++++++++------------
 1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/drivers/iio/adc/ti-ads1015.c b/drivers/iio/adc/ti-ads1015.c
index d48515682dee..ed911776e283 100644
--- a/drivers/iio/adc/ti-ads1015.c
+++ b/drivers/iio/adc/ti-ads1015.c
@@ -242,27 +242,34 @@ static
 int ads1015_get_adc_result(struct ads1015_data *data, int chan, int *val)
 {
 	int ret, pga, dr, conv_time;
-	bool change;
+	unsigned int old, mask, cfg;
 
 	if (chan < 0 || chan >= ADS1015_CHANNELS)
 		return -EINVAL;
 
+	ret = regmap_read(data->regmap, ADS1015_CFG_REG, &old);
+	if (ret)
+		return ret;
+
 	pga = data->channel_data[chan].pga;
 	dr = data->channel_data[chan].data_rate;
+	mask = ADS1015_CFG_MUX_MASK | ADS1015_CFG_PGA_MASK |
+		ADS1015_CFG_DR_MASK;
+	cfg = chan << ADS1015_CFG_MUX_SHIFT | pga << ADS1015_CFG_PGA_SHIFT |
+		dr << ADS1015_CFG_DR_SHIFT;
 
-	ret = regmap_update_bits_check(data->regmap, ADS1015_CFG_REG,
-				       ADS1015_CFG_MUX_MASK |
-				       ADS1015_CFG_PGA_MASK |
-				       ADS1015_CFG_DR_MASK,
-				       chan << ADS1015_CFG_MUX_SHIFT |
-				       pga << ADS1015_CFG_PGA_SHIFT |
-				       dr << ADS1015_CFG_DR_SHIFT,
-				       &change);
-	if (ret < 0)
+	cfg = (old & ~mask) | (cfg & mask);
+
+	ret = regmap_write(data->regmap, ADS1015_CFG_REG, cfg);
+	if (ret)
 		return ret;
 
-	if (change || data->conv_invalid) {
-		conv_time = DIV_ROUND_UP(USEC_PER_SEC, data->data_rate[dr]);
+	if (old != cfg || data->conv_invalid) {
+		int dr_old = (old & ADS1015_CFG_DR_MASK) >>
+				ADS1015_CFG_DR_SHIFT;
+
+		conv_time = DIV_ROUND_UP(USEC_PER_SEC, data->data_rate[dr_old]);
+		conv_time += DIV_ROUND_UP(USEC_PER_SEC, data->data_rate[dr]);
 		usleep_range(conv_time, conv_time + 1);
 		data->conv_invalid = false;
 	}
-- 
2.14.1