On 7/9/21 5:11 AM, Uwe Kleine-König wrote:
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@xxxxxxxxxxxxxx>
---
drivers/iio/adc/ti-ads7950.c | 1 -
1 file changed, 1 deletion(-)
diff --git a/drivers/iio/adc/ti-ads7950.c b/drivers/iio/adc/ti-ads7950.c
index 2383eacada87..a2b83f0bd526 100644
--- a/drivers/iio/adc/ti-ads7950.c
+++ b/drivers/iio/adc/ti-ads7950.c
@@ -568,7 +568,6 @@ static int ti_ads7950_probe(struct spi_device *spi)
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);
Yes, it seems like the SPI_CS_WORD flag should have replaced this (it's
been too long, I can't remember if it was intentional). And removing it
doesn't seem to break anything for me.
Reviewed-by: David Lechner <david@xxxxxxxxxxxxxx>
Tested-by: David Lechner <david@xxxxxxxxxxxxxx>
