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[PATCH 4.9 11/32] iio: adc: ti-ads1015: avoid getting stale result after runtime resume

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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

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

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.

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 |   18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

--- a/drivers/iio/adc/ti-ads1015.c
+++ b/drivers/iio/adc/ti-ads1015.c
@@ -176,6 +176,12 @@ 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)
@@ -254,9 +260,10 @@ 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);
@@ -624,6 +631,8 @@ 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;
@@ -679,10 +688,15 @@ 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
 

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[PATCH 4.9 00/32] 4.9.49-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-08 15:30 +0200
  [PATCH 4.9 12/32] iio: adc: ti-ads1015: dont return invalid value from buffer setup callbacks Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-08 15:30 +0200
  [PATCH 4.9 28/32] cs5536: add support for IDE controller variant Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-08 15:30 +0200
  [PATCH 4.9 03/32] usb: Add device quirk for Logitech HD Pro Webcam C920-C Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-08 15:30 +0200
  [PATCH 4.9 25/32] s390/mm: avoid empty zero pages for KVM guests to avoid postcopy hangs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-08 15:30 +0200
  [PATCH 4.9 04/32] usb:xhci:Fix regression when ATI chipsets detected Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-08 15:30 +0200
  [PATCH 4.9 18/32] Input: trackpoint - assume 3 buttons when buttons detection fails Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-08 15:30 +0200
  [PATCH 4.9 09/32] iio: adc: ti-ads1015: fix scale information for ADS1115 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-08 15:30 +0200
  [PATCH 4.9 30/32] scsi: sg: recheck MMAP_IO request length with lock held Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-08 15:30 +0200
  [PATCH 4.9 16/32] intel_th: pci: Add Cannon Lake PCH-LP support Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-08 15:30 +0200
  [PATCH 4.9 26/32] drm/nouveau/pci/msi: disable MSI on big-endian platforms by default Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-08 15:30 +0200
  [PATCH 4.9 07/32] staging/rts5208: fix incorrect shift to extract upper nybble Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-08 15:30 +0200
  [PATCH 4.9 27/32] workqueue: Fix flag collision Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-08 15:30 +0200
  [PATCH 4.9 29/32] scsi: sg: protect against races between mmap() and SG_SET_RESERVED_SIZE Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-08 15:30 +0200
  [PATCH 4.9 20/32] Bluetooth: Add support of 13d3:3494 RTL8723BE device Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-08 15:40 +0200
  [PATCH 4.9 17/32] ath10k: fix memory leak in rx ring buffer allocation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-08 15:40 +0200
  [PATCH 4.9 14/32] driver core: bus: Fix a potential double free Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-08 15:40 +0200
  [PATCH 4.9 11/32] iio: adc: ti-ads1015: avoid getting stale result after runtime resume Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-08 15:40 +0200
  [PATCH 4.9 15/32] intel_th: pci: Add Cannon Lake PCH-H support Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-08 15:40 +0200
  [PATCH 4.9 13/32] iio: adc: ti-ads1015: add adequate wait time to get correct conversion Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-08 15:40 +0200
  [PATCH 4.9 21/32] iwlwifi: pci: add new PCI ID for 7265D Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-08 15:40 +0200
  [PATCH 4.9 10/32] iio: adc: ti-ads1015: enable conversion when CONFIG_PM is not set Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-08 15:40 +0200
  [PATCH 4.9 19/32] rtlwifi: rtl_pci_probe: Fix fail path of _rtl_pci_find_adapter Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-08 15:40 +0200
  [PATCH 4.9 01/32] usb: quirks: add delay init quirk for Corsair Strafe RGB keyboard Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-08 15:40 +0200
  Re: [PATCH 4.9 00/32] 4.9.49-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-09-08 20:40 +0200
  Re: [PATCH 4.9 00/32] 4.9.49-stable review Guenter Roeck <linux@roeck-us.net> - 2017-09-09 15:50 +0200

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