Hi Justin, On 1/24/19 5:56 PM, justinpopo6@xxxxxxxxx wrote: > From: Justin Chen <justinpopo6@xxxxxxxxx> > > To read a channel we require 3 cycles to send, process, and receive > the data. The transfer buffer for the third transaction is left blank. > This leaves it up to the SPI driver to decide what to do. > > In one particular case, if the tx buffer is not set the spi driver > sets it to 0xff. This puts the ADC in a alarm programming state, > therefore the following read to a channel becomes erroneous. > > Instead of leaving us to the mercy of the SPI driver, we send the > ADC cmd on the third transaction to prevent inconsistent behavior. Do you think this warrants a Fixes: tag? > > Signed-off-by: Justin Chen <justinpopo6@xxxxxxxxx> > --- > drivers/iio/adc/ti-ads7950.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/iio/adc/ti-ads7950.c b/drivers/iio/adc/ti-ads7950.c > index 0ad6359..5453e10 100644 > --- a/drivers/iio/adc/ti-ads7950.c > +++ b/drivers/iio/adc/ti-ads7950.c > @@ -422,6 +422,7 @@ static int ti_ads7950_probe(struct spi_device *spi) > st->scan_single_xfer[1].tx_buf = &st->single_tx; > st->scan_single_xfer[1].len = 2; > st->scan_single_xfer[1].cs_change = 1; > + st->scan_single_xfer[2].rx_buf = &st->single_tx; Should this be st->scan_single_xfer[2].tx_buf? > st->scan_single_xfer[2].rx_buf = &st->single_rx; > st->scan_single_xfer[2].len = 2; > > -- Florian
