Commit 73e3e3fc authored by Akinobu Mita's avatar Akinobu Mita Committed by Jonathan Cameron
Browse files

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



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: default avatarAkinobu Mita <akinobu.mita@gmail.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
parent e8245c68

drivers/iio/adc/ti-ads1015.c

+16 −2
Original line number Diff line number Diff line
@@ -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 ads1015_data *data, int chan, int *val) 
	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_client *client, 
	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 device *dev) 
{

	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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