Le 02/12/2019 à 15:13, Andrea Merello a écrit :
drivers/iio/adc/ad7949.c | 22 +++++++++++++++++-----
1 file changed, 17 insertions(+), 5 deletions(-)
diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c
index 5c2b3446fa4a..2c6f60edb7ce 100644
--- a/drivers/iio/adc/ad7949.c
+++ b/drivers/iio/adc/ad7949.c
@@ -89,6 +89,7 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
unsigned int channel)
{
int ret;
+ int i;
int bits_per_word = ad7949_adc->resolution;
int mask = GENMASK(ad7949_adc->resolution, 0);
struct spi_message msg;
@@ -100,12 +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);
Signed-off-by: Charles-Antoine Couret <charles-antoine.couret@xxxxxxxxxxxxx>
Regards,
Charles-Antoine Couret
