iio: adc: ad7768-1: set MOSI idle state to prevent accidental reset

Datasheet recommends Setting the MOSI idle state to high in order to
prevent accidental reset of the device when SCLK is free running.
This happens when the controller clocks out a 1 followed by 63 zeros
while the CS is held low.

Check if SPI controller supports SPI_MOSI_IDLE_HIGH flag and set it.

Fixes: a5f8c7da3dbe ("iio: adc: Add AD7768-1 ADC basic support")
Signed-off-by: Jonathan Santos <Jonathan.Santos@analog.com>
Reviewed-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
Link: https://patch.msgid.link/c2a2b0f3d54829079763a5511359a1fa80516cfb.1741268122.git.Jonathan.Santos@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/adc/ad7768-1.c b/drivers/iio/adc/ad7768-1.c
index 09e7cccfd51cfd45dff3bcf3a324f6f57016564e..a75247cdcaa7bf0deeeb33f27bb4fbb79c204af5 100644 (file)
--- a/drivers/iio/adc/ad7768-1.c
+++ b/drivers/iio/adc/ad7768-1.c
@@ -572,6 +572,21 @@ static int ad7768_probe(struct spi_device *spi)
                return -ENOMEM;
 
        st = iio_priv(indio_dev);
+       /*
+        * Datasheet recommends SDI line to be kept high when data is not being
+        * clocked out of the controller and the spi clock is free running,
+        * to prevent accidental reset.
+        * Since many controllers do not support the SPI_MOSI_IDLE_HIGH flag
+        * yet, only request the MOSI idle state to enable if the controller
+        * supports it.
+        */
+       if (spi->controller->mode_bits & SPI_MOSI_IDLE_HIGH) {
+               spi->mode |= SPI_MOSI_IDLE_HIGH;
+               ret = spi_setup(spi);
+               if (ret < 0)
+                       return ret;
+       }
+
        st->spi = spi;
 
        st->vref = devm_regulator_get(&spi->dev, "vref");