Patch "iio: adc: ti-ads1015: avoid getting stale result after runtime resume" has been added to the 4.12-stable tree

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

iio: adc: ti-ads1015: avoid getting stale result after runtime resume

to the 4.12-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-avoid-getting-stale-result-after-runtime-resume.patch
and it can be found in the queue-4.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Akinobu Mita <[email protected]>
Date: Fri, 21 Jul 2017 00:24:20 +0900
Subject: iio: adc: ti-ads1015: avoid getting stale result after runtime resume

From: Akinobu Mita <[email protected]>

commit 73e3e3fc50de50cfd68e945d85679c983ed31bd9 upstream.

This driver assumes that the device is operating in the continuous conversion mode which performs the conversion continuously. So this driver doesn't insert a wait time before reading the conversion register if the configuration is not changed from a previous request.

This assumption is broken if the device is runtime suspended and entered a power-down state. The forthcoming request causes reading a stale result from the conversion register as the device is runtime resumed just before.

Fix it by adding a flag to detect that condition and insert a necessary wait time.

---
 drivers/iio/adc/ti-ads1015.c |   18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

@@ -177,6 +177,12 @@ struct ads1015_data {
 	struct ads1015_channel_data channel_data[ADS1015_CHANNELS];
 
 	unsigned int *data_rate;
+	/*
+	 * Set to true when the ADC is switched to the continuous-conversion
+	 * mode and exits from a power-down state.  This flag is used to avoid
+	 * getting the stale result from the conversion register.
+	 */
+	bool conv_invalid;
 };
 
 static bool ads1015_is_writeable_reg(struct device *dev, unsigned int reg)

@@ -255,9 +261,10 @@ int ads1015_get_adc_result(struct ads101
 	if (ret < 0)
 		return ret;
 
-	if (change) {
+	if (change || data->conv_invalid) {
 		conv_time = DIV_ROUND_UP(USEC_PER_SEC, data->data_rate[dr]);
 		usleep_range(conv_time, conv_time + 1);
+		data->conv_invalid = false;
 	}
 
 	return regmap_read(data->regmap, ADS1015_CONV_REG, val);

@@ -630,6 +637,8 @@ static int ads1015_probe(struct i2c_clie
 	if (ret)
 		return ret;
 
+	data->conv_invalid = true;
+
 	ret = pm_runtime_set_active(&client->dev);
 	if (ret)
 		goto err_buffer_cleanup;

@@ -685,10 +694,15 @@ static int ads1015_runtime_resume(struct
 {
 	struct iio_dev *indio_dev = i2c_get_clientdata(to_i2c_client(dev));
 	struct ads1015_data *data = iio_priv(indio_dev);
+	int ret;
 
-	return regmap_update_bits(data->regmap, ADS1015_CFG_REG,
+	ret = regmap_update_bits(data->regmap, ADS1015_CFG_REG,
 				  ADS1015_CFG_MOD_MASK,
 				  ADS1015_CONTINUOUS << ADS1015_CFG_MOD_SHIFT);
+	if (!ret)
+		data->conv_invalid = true;
+
+	return ret;
 }
 #endif
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.12/iio-adc-ti-ads1015-enable-conversion-when-config_pm-is-not-set.patch queue-4.12/iio-adc-ti-ads1015-add-adequate-wait-time-to-get-correct-conversion.patch queue-4.12/iio-adc-ti-ads1015-don-t-return-invalid-value-from-buffer-setup-callbacks.patch queue-4.12/iio-adc-ti-ads1015-fix-incorrect-data-rate-setting-update.patch queue-4.12/iio-adc-ti-ads1015-fix-scale-information-for-ads1115.patch queue-4.12/iio-adc-ti-ads1015-avoid-getting-stale-result-after-runtime-resume.patch