From 4744d4e2afebf9644a439da9ca73d822fdd67bd9 Mon Sep 17 00:00:00 2001 From: Akinobu Mita Date: Fri, 21 Jul 2017 00:24:22 +0900 Subject: iio: adc: ti-ads1015: add adequate wait time to get correct conversion This driver assumes that the device is operating in the continuous conversion mode which performs the conversion continuously. So this driver inserts a wait time before reading the conversion register if the configuration is changed from a previous request. Currently, the wait time is only the period required for a single conversion that is calculated as the reciprocal of the sampling frequency. However we also need to wait for the the previous conversion to complete. Otherwise we probably get the conversion result for the previous configuration when the sampling frequency is lower. Cc: Daniel Baluta Signed-off-by: Akinobu Mita Cc: Signed-off-by: Jonathan Cameron --- drivers/iio/adc/ti-ads1015.c | 31 +++++++++++++++++++------------ 1 file changed, 19 insertions(+), 12 deletions(-) (limited to 'drivers/iio') diff --git a/drivers/iio/adc/ti-ads1015.c b/drivers/iio/adc/ti-ads1015.c index d48515682dee..ed911776e283 100644 --- a/drivers/iio/adc/ti-ads1015.c +++ b/drivers/iio/adc/ti-ads1015.c @@ -242,27 +242,34 @@ static int ads1015_get_adc_result(struct ads1015_data *data, int chan, int *val) { int ret, pga, dr, conv_time; - bool change; + unsigned int old, mask, cfg; if (chan < 0 || chan >= ADS1015_CHANNELS) return -EINVAL; + ret = regmap_read(data->regmap, ADS1015_CFG_REG, &old); + if (ret) + return ret; + pga = data->channel_data[chan].pga; dr = data->channel_data[chan].data_rate; + mask = ADS1015_CFG_MUX_MASK | ADS1015_CFG_PGA_MASK | + ADS1015_CFG_DR_MASK; + cfg = chan << ADS1015_CFG_MUX_SHIFT | pga << ADS1015_CFG_PGA_SHIFT | + dr << ADS1015_CFG_DR_SHIFT; - ret = regmap_update_bits_check(data->regmap, ADS1015_CFG_REG, - ADS1015_CFG_MUX_MASK | - ADS1015_CFG_PGA_MASK | - ADS1015_CFG_DR_MASK, - chan << ADS1015_CFG_MUX_SHIFT | - pga << ADS1015_CFG_PGA_SHIFT | - dr << ADS1015_CFG_DR_SHIFT, - &change); - if (ret < 0) + cfg = (old & ~mask) | (cfg & mask); + + ret = regmap_write(data->regmap, ADS1015_CFG_REG, cfg); + if (ret) return ret; - if (change || data->conv_invalid) { - conv_time = DIV_ROUND_UP(USEC_PER_SEC, data->data_rate[dr]); + if (old != cfg || data->conv_invalid) { + int dr_old = (old & ADS1015_CFG_DR_MASK) >> + ADS1015_CFG_DR_SHIFT; + + conv_time = DIV_ROUND_UP(USEC_PER_SEC, data->data_rate[dr_old]); + conv_time += DIV_ROUND_UP(USEC_PER_SEC, data->data_rate[dr]); usleep_range(conv_time, conv_time + 1); data->conv_invalid = false; } -- cgit