From 73e3e3fc50de50cfd68e945d85679c983ed31bd9 Mon Sep 17 00:00:00 2001 From: Akinobu Mita Date: Fri, 21 Jul 2017 00:24:20 +0900 Subject: [PATCH] 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 Signed-off-by: Akinobu Mita Cc: Signed-off-by: Jonathan Cameron --- drivers/iio/adc/ti-ads1015.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/drivers/iio/adc/ti-ads1015.c b/drivers/iio/adc/ti-ads1015.c index 9d77e837c09b..2f52b149f49a 100644 --- a/drivers/iio/adc/ti-ads1015.c +++ b/drivers/iio/adc/ti-ads1015.c @@ -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 -- 2.20.1