diff options
Diffstat (limited to 'drivers/iio/adc/ad7949.c')
| -rw-r--r-- | drivers/iio/adc/ad7949.c | 49 |
1 files changed, 20 insertions, 29 deletions
diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c index ac0ffff6c5ae..6b51bfcad0d0 100644 --- a/drivers/iio/adc/ad7949.c +++ b/drivers/iio/adc/ad7949.c @@ -57,29 +57,11 @@ struct ad7949_adc_chip { u32 buffer ____cacheline_aligned; }; -static bool ad7949_spi_cfg_is_read_back(struct ad7949_adc_chip *ad7949_adc) -{ - if (!(ad7949_adc->cfg & AD7949_CFG_READ_BACK)) - return true; - - return false; -} - -static int ad7949_spi_bits_per_word(struct ad7949_adc_chip *ad7949_adc) -{ - int ret = ad7949_adc->resolution; - - if (ad7949_spi_cfg_is_read_back(ad7949_adc)) - ret += AD7949_CFG_REG_SIZE_BITS; - - return ret; -} - static int ad7949_spi_write_cfg(struct ad7949_adc_chip *ad7949_adc, u16 val, u16 mask) { int ret; - int bits_per_word = ad7949_spi_bits_per_word(ad7949_adc); + int bits_per_word = ad7949_adc->resolution; int shift = bits_per_word - AD7949_CFG_REG_SIZE_BITS; struct spi_message msg; struct spi_transfer tx[] = { @@ -107,7 +89,8 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val, unsigned int channel) { int ret; - int bits_per_word = ad7949_spi_bits_per_word(ad7949_adc); + int i; + int bits_per_word = ad7949_adc->resolution; int mask = GENMASK(ad7949_adc->resolution, 0); struct spi_message msg; struct spi_transfer tx[] = { @@ -118,12 +101,23 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val, }, }; - ret = ad7949_spi_write_cfg(ad7949_adc, - channel << AD7949_OFFSET_CHANNEL_SEL, - AD7949_MASK_CHANNEL_SEL); - if (ret) - return ret; + /* + * 1: write CFG for sample N and read old data (sample N-2) + * 2: if CFG was not changed since sample N-1 then we'll get good data + * at the next xfer, so we bail out now, otherwise we write something + * and we read garbage (sample N-1 configuration). + */ + for (i = 0; i < 2; i++) { + ret = ad7949_spi_write_cfg(ad7949_adc, + channel << AD7949_OFFSET_CHANNEL_SEL, + AD7949_MASK_CHANNEL_SEL); + if (ret) + return ret; + if (channel == ad7949_adc->current_channel) + break; + } + /* 3: write something and read actual data */ ad7949_adc->buffer = 0; spi_message_init_with_transfers(&msg, tx, 1); ret = spi_sync(ad7949_adc->spi, &msg); @@ -138,10 +132,7 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val, ad7949_adc->current_channel = channel; - if (ad7949_spi_cfg_is_read_back(ad7949_adc)) - *val = (ad7949_adc->buffer >> AD7949_CFG_REG_SIZE_BITS) & mask; - else - *val = ad7949_adc->buffer & mask; + *val = ad7949_adc->buffer & mask; return 0; } |