[PATCH] drivers: iio: adc: ltc2497: fix LSB shift

Ian Ray
2023-01-27T15:02:05Z

Correct the "sub_lsb" shift for both ltc2497 and ltc2499.

An earlier version of the code shifted by 14 but this was a consequence
of reading three bytes into a __be32 buffer and using be32_to_cpu(), so
eight extra bits needed to be skipped. Now we use get_unaligned_be24()
and thus the additional skip is wrong.

Fixes 2187cfe ("drivers: iio: adc: ltc2497: LTC2499 support")
Signed-off-by: Ian Ray <ian.ray@ge.com>
---
drivers/iio/adc/ltc2497.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/adc/ltc2497.c b/drivers/iio/adc/ltc2497.c
index 17370c5..ec198c6 100644
--- a/drivers/iio/adc/ltc2497.c
+++ b/drivers/iio/adc/ltc2497.c
@@ -28,7 +28,6 @@ struct ltc2497_driverdata {
struct ltc2497core_driverdata common_ddata;
struct i2c_client *client;
u32 recv_size;
- u32 sub_lsb;
/*
* DMA (thus cache coherency maintenance) may require the
* transfer buffers to live in their own cache lines.
@@ -65,10 +64,10 @@ static int ltc2497_result_and_measure(struct ltc2497core_driverdata *ddata,
* equivalent to a sign extension.
*/
if (st->recv_size == 3) {
- *val = (get_unaligned_be24(st->data.d8) >> st->sub_lsb)
+ *val = (get_unaligned_be24(st->data.d8) >> 6)
- BIT(ddata->chip_info->resolution + 1);
} else {
- *val = (be32_to_cpu(st->data.d32) >> st->sub_lsb)
+ *val = (be32_to_cpu(st->data.d32) >> 6)
- BIT(ddata->chip_info->resolution + 1);
}

@@ -122,7 +121,6 @@ static int ltc2497_probe(struct i2c_client *client)
st->common_ddata.chip_info = chip_info;

resolution = chip_info->resolution;
- st->sub_lsb = 31 - (resolution + 1);
st->recv_size = BITS_TO_BYTES(resolution) + 1;

return ltc2497core_probe(dev, indio_dev);
--
2.10.1