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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: Akinobu Mita <akinobu.mita@gmail.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
Akinobu Mita 2017-07-21 00:24:20 +09:00 committed by Jonathan Cameron
parent e8245c6835
commit 73e3e3fc50
1 changed files with 16 additions and 2 deletions
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18
drivers/iio/adc/ti-ads1015.c
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@ -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