staging: iio: ad2s1210: Fix SPI reading

commit 5e4f99a6b788047b0b8a7496c2e0c8f372f6edf2 upstream.

If the serial interface is used, the 8-bit address should be latched using
the rising edge of the WR/FSYNC signal.

This basically means that a CS change is required between the first byte
sent, and the second one.
This change splits the single-transfer transfer of 2 bytes into 2 transfers
with a single byte, and CS change in-between.

Note fixes tag is not accurate, but reflects a point beyond which there
are too many refactors to make backporting straight forward.

Fixes: b19e9ad5e2cb ("staging:iio:resolver:ad2s1210 general driver cleanup.")
Signed-off-by: Dragos Bogdan <dragos.bogdan@analog.com>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.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/staging/iio/resolver/ad2s1210.c b/drivers/staging/iio/resolver/ad2s1210.c
index 598f0faa48c8212da462e4ee9a21ddb8c6bf0fb0..0f5eb2bf5f73b0530b77e74c4f60d807c795bffc 100644 (file)
--- a/drivers/staging/iio/resolver/ad2s1210.c
+++ b/drivers/staging/iio/resolver/ad2s1210.c
@@ -126,17 +126,24 @@ static int ad2s1210_config_write(struct ad2s1210_state *st, u8 data)
 static int ad2s1210_config_read(struct ad2s1210_state *st,
                                unsigned char address)
 {
-       struct spi_transfer xfer = {
-               .len = 2,
-               .rx_buf = st->rx,
-               .tx_buf = st->tx,
+       struct spi_transfer xfers[] = {
+               {
+                       .len = 1,
+                       .rx_buf = &st->rx[0],
+                       .tx_buf = &st->tx[0],
+                       .cs_change = 1,
+               }, {
+                       .len = 1,
+                       .rx_buf = &st->rx[1],
+                       .tx_buf = &st->tx[1],
+               },
        };
        int ret = 0;
 
        ad2s1210_set_mode(MOD_CONFIG, st);
        st->tx[0] = address | AD2S1210_MSB_IS_HIGH;
        st->tx[1] = AD2S1210_REG_FAULT;
-       ret = spi_sync_transfer(st->sdev, &xfer, 1);
+       ret = spi_sync_transfer(st->sdev, xfers, 2);
        if (ret < 0)
                return ret;
        st->old_data = true;