From: Thomas Betker <[email protected]>

This patch has been added to the 3.18 stable tree. If you have any
objections, please let us know.

===============

[ Upstream commit 97ffae1d30c3f6ceee67d5b0d3e540c08c13c744 ]

The VREFN channel is bipolar, not unipolar. Small negative values do
occur (e.g., -1mV), and unsigned conversion maps them incorrectly to
large positive values (about +1V), so fix this.

Signed-off-by: Thomas Betker <[email protected]>
Cc: <[email protected]>
Signed-off-by: Jonathan Cameron <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
---
 drivers/iio/adc/xilinx-xadc-core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iio/adc/xilinx-xadc-core.c 
b/drivers/iio/adc/xilinx-xadc-core.c
index 6fa629b..ce93bd8 100644
--- a/drivers/iio/adc/xilinx-xadc-core.c
+++ b/drivers/iio/adc/xilinx-xadc-core.c
@@ -997,7 +997,7 @@ static const struct iio_event_spec xadc_voltage_events[] = {
        .num_event_specs = (_alarm) ? ARRAY_SIZE(xadc_voltage_events) : 0, \
        .scan_index = (_scan_index), \
        .scan_type = { \
-               .sign = 'u', \
+               .sign = ((_addr) == XADC_REG_VREFN) ? 's' : 'u', \
                .realbits = 12, \
                .storagebits = 16, \
                .shift = 4, \
-- 
2.1.0

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