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

Greg Kroah-Hartman
2017-09-08T13:33:16Z

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