Patch "iio: adc: ti-ads1015: add adequate wait time to get correct conversion" has been added to the 4.13-stable tree

[<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 conversion

to the 4.13-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     iio-adc-ti-ads1015-add-adequate-wait-time-to-get-correct-conversion.patch
and it can be found in the queue-4.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>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

From: Akinobu Mita <akinobu.mita@gmail.com>

commit 4744d4e2afebf9644a439da9ca73d822fdd67bd9 upstream.

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>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- 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;
 	}


Patches currently in stable-queue which might be from akinobu.mita@gmail.com are

queue-4.13/iio-adc-ti-ads1015-enable-conversion-when-config_pm-is-not-set.patch
queue-4.13/iio-adc-ti-ads1015-add-adequate-wait-time-to-get-correct-conversion.patch
queue-4.13/iio-adc-ti-ads1015-don-t-return-invalid-value-from-buffer-setup-callbacks.patch
queue-4.13/iio-adc-ti-ads1015-fix-incorrect-data-rate-setting-update.patch
queue-4.13/iio-adc-ti-ads1015-fix-scale-information-for-ads1115.patch
queue-4.13/iio-adc-ti-ads1015-avoid-getting-stale-result-after-runtime-resume.patch