[PATCH v3 07/27] staging: iio: resolver: ad2s1210: always use 16-bit value for raw read

David Lechner
2023-09-29T17:25:54Z

From: David Lechner <david@lechnology.com>

From: David Lechner <dlechner@baylibre.com>

This removes the special handling for resolutions lower than 16 bits.
This will allow us to use a fixed scale independent of the resolution.

A new sample field is added to store the raw data instead of reusing
the config mode rx buffer so that we don't have to do a cast or worry
about unaligned access.

Also, for the record, according to the datasheet, the logic for the
special handling based on hysteresis that was removed was incorrect.

Signed-off-by: David Lechner <dlechner@baylibre.com>
---

v3 changes:
* Added __be16 sample field to state struct and use instead of rx buffer.

drivers/staging/iio/resolver/ad2s1210.c | 24 ++++++++----------------
1 file changed, 8 insertions(+), 16 deletions(-)

diff --git a/drivers/staging/iio/resolver/ad2s1210.c b/drivers/staging/iio/resolver/ad2s1210.c
index 832f86bf15e5..f9774dff2df4 100644
--- a/drivers/staging/iio/resolver/ad2s1210.c
+++ b/drivers/staging/iio/resolver/ad2s1210.c
@@ -95,7 +95,11 @@ struct ad2s1210_state {
bool hysteresis;
u8 resolution;
enum ad2s1210_mode mode;
- u8 rx[2] __aligned(IIO_DMA_MINALIGN);
+ /** For reading raw sample value via SPI. */
+ __be16 sample __aligned(IIO_DMA_MINALIGN);
+ /** SPI transmit buffer. */
+ u8 rx[2];
+ /** SPI receive buffer. */
u8 tx[2];
};

@@ -464,10 +468,7 @@ static int ad2s1210_read_raw(struct iio_dev *indio_dev,
long m)
{
struct ad2s1210_state *st = iio_priv(indio_dev);
- u16 negative;
int ret = 0;
- u16 pos;
- s16 vel;

mutex_lock(&st->lock);
gpiod_set_value(st->gpios[AD2S1210_SAMPLE], 0);
@@ -487,26 +488,17 @@ static int ad2s1210_read_raw(struct iio_dev *indio_dev,
}
if (ret < 0)
goto error_ret;
- ret = spi_read(st->sdev, st->rx, 2);
+ ret = spi_read(st->sdev, &st->sample, 2);
if (ret < 0)
goto error_ret;

switch (chan->type) {
case IIO_ANGL:
- pos = be16_to_cpup((__be16 *)st->rx);
- if (st->hysteresis)
- pos >>= 16 - st->resolution;
- *val = pos;
+ *val = be16_to_cpu(st->sample);
ret = IIO_VAL_INT;
break;
case IIO_ANGL_VEL:
- vel = be16_to_cpup((__be16 *)st->rx);
- vel >>= 16 - st->resolution;
- if (vel & 0x8000) {
- negative = (0xffff >> st->resolution) << st->resolution;
- vel |= negative;
- }
- *val = vel;
+ *val = (s16)be16_to_cpu(st->sample);
ret = IIO_VAL_INT;
break;
default:

--
2.42.0