iio: adc: xilinx-xadc: Fix sequencer mode in postdisable for dual mux

xadc_postdisable() unconditionally sets the sequencer to continuous
mode. For dual external multiplexer configurations this is incorrect:
simultaneous sampling mode is required so that ADC-A samples through
the mux on VAUX[0-7] while ADC-B simultaneously samples through the
mux on VAUX[8-15]. In continuous mode only ADC-A is active, so
VAUX[8-15] channels return incorrect data.

Since postdisable is also called from xadc_probe() to set the initial
idle state, the wrong sequencer mode is active from the moment the
driver loads.

The preenable path already uses xadc_get_seq_mode() which returns
SIMULTANEOUS for dual mux. Fix postdisable to do the same.

Fixes: bdc8cda1d010 ("iio:adc: Add Xilinx XADC driver")
Cc: stable@vger.kernel.org
Signed-off-by: Christofer Jonason <christofer.jonason@guidelinegeo.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Reviewed-by: Salih Erim <salih.erim@amd.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/adc/xilinx-xadc-core.c b/drivers/iio/adc/xilinx-xadc-core.c
index e257c1b94a5f747c44729583da77cf012c36024c..3980dfacbcd79e7019b8a5146ee10f935cbdda4d 100644 (file)
--- a/drivers/iio/adc/xilinx-xadc-core.c
+++ b/drivers/iio/adc/xilinx-xadc-core.c
@@ -817,6 +817,7 @@ static int xadc_postdisable(struct iio_dev *indio_dev)
 {
        struct xadc *xadc = iio_priv(indio_dev);
        unsigned long scan_mask;
+       int seq_mode;
        int ret;
        int i;
 
@@ -824,6 +825,12 @@ static int xadc_postdisable(struct iio_dev *indio_dev)
        for (i = 0; i < indio_dev->num_channels; i++)
                scan_mask |= BIT(indio_dev->channels[i].scan_index);
 
+       /*
+        * Use the correct sequencer mode for the idle state: simultaneous
+        * mode for dual external mux configurations, continuous otherwise.
+        */
+       seq_mode = xadc_get_seq_mode(xadc, scan_mask);
+
        /* Enable all channels and calibration */
        ret = xadc_write_adc_reg(xadc, XADC_REG_SEQ(0), scan_mask & 0xffff);
        if (ret)
@@ -834,11 +841,11 @@ static int xadc_postdisable(struct iio_dev *indio_dev)
                return ret;
 
        ret = xadc_update_adc_reg(xadc, XADC_REG_CONF1, XADC_CONF1_SEQ_MASK,
-               XADC_CONF1_SEQ_CONTINUOUS);
+                                 seq_mode);
        if (ret)
                return ret;
 
-       return xadc_power_adc_b(xadc, XADC_CONF1_SEQ_CONTINUOUS);
+       return xadc_power_adc_b(xadc, seq_mode);
 }
 
 static int xadc_preenable(struct iio_dev *indio_dev)