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

Jonathan Cameron
2023-09-30T14:41:17Z

On Fri, 29 Sep 2023 12:23:12 -0500
David Lechner <dlechner@baylibre.com> wrote:

> 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>
LGTM

Applied.

Thanks,

Jonathan

> ---
>
> 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:
>