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

PATCH [email protected] 1 participant 1 message Aug 20, 2017

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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.

Quoted 1 line

From 4744d4e2afebf9644a439da9ca73d822fdd67bd9 Mon Sep 17 00:00:00 2001

From: Akinobu Mita <[email protected]>
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 <[email protected]>
Signed-off-by Akinobu Mita <[email protected]>
Cc <[email protected]>
Signed-off-by Jonathan Cameron <[email protected]>
---
 drivers/iio/adc/ti-ads1015.c | 31 +++++++++++++++++++------------
 1 file changed, 19 insertions(+), 12 deletions(-)
drivers/iio/adc/ti-ads1015.c +19 -12
index d48515682dee..ed911776e283 100644
@@ -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;
 	}
Signature · 1 line
2.14.1