From: Uwe Kleine-König u.kleine-koenig@pengutronix.de
commit 9898cb24e454602beb6e17bacf9f97b26c85c955 upstream.
The ADS7950 requires that CS is deasserted after each SPI word. Before commit e2540da86ef8 ("iio: adc: ti-ads7950: use SPI_CS_WORD to reduce CPU usage") the driver used a message with one spi transfer per channel where each but the last one had .cs_change set to enforce a CS toggle. This was wrongly translated into a message with a single transfer and .cs_change set which results in a CS toggle after each word but the last which corrupts the first adc conversion of all readouts after the first readout.
Fixes: e2540da86ef8 ("iio: adc: ti-ads7950: use SPI_CS_WORD to reduce CPU usage") Signed-off-by: Uwe Kleine-König u.kleine-koenig@pengutronix.de Reviewed-by: David Lechner david@lechnology.com Tested-by: David Lechner david@lechnology.com Cc: Stable@vger.kernel.org Link: https://lore.kernel.org/r/20210709101110.1814294-1-u.kleine-koenig@pengutron... Signed-off-by: Jonathan Cameron Jonathan.Cameron@huawei.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/iio/adc/ti-ads7950.c | 1 - 1 file changed, 1 deletion(-)
--- a/drivers/iio/adc/ti-ads7950.c +++ b/drivers/iio/adc/ti-ads7950.c @@ -569,7 +569,6 @@ static int ti_ads7950_probe(struct spi_d st->ring_xfer.tx_buf = &st->tx_buf[0]; st->ring_xfer.rx_buf = &st->rx_buf[0]; /* len will be set later */ - st->ring_xfer.cs_change = true;
spi_message_add_tail(&st->ring_xfer, &st->ring_msg);