drivers: iio: adc: ltc2497: fix LSB shift

commit 6327a930ab7bfa1ab33bcdffd5f5f4b1e7131504 upstream.

Correct the "sub_lsb" shift for the ltc2497 and drop the sub_lsb element
which is now constant.

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: 2187cfeb3626 ("drivers: iio: adc: ltc2497: LTC2499 support")
Signed-off-by: Ian Ray <ian.ray@ge.com>
Link: https://lore.kernel.org/r/20230127125714.44608-1-ian.ray@ge.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/iio/adc/ltc2497.c b/drivers/iio/adc/ltc2497.c
index 556f10dfb5023f7da9f2d75247f820ba1774e6c7..e1e14f5d237d2fa920d5b7fe6cec241115167bf1 100644 (file)
--- 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);