iio: adc: aspeed: clear reference voltage bits before configuring vref

Ensures the reference voltage bits are cleared in the ADC engine
control register before configuring the voltage reference. This
avoids potential misconfigurations caused by residual bits.

Fixes: 1b5ceb55fec2 ("iio: adc: aspeed: Support ast2600 adc.")
Signed-off-by: Billy Tsai <billy_tsai@aspeedtech.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/adc/aspeed_adc.c b/drivers/iio/adc/aspeed_adc.c
index 4be44c524b4daa9d7842de0df57cda4f21c2861b..83a9885b9ae4da54f1e0a2001a730f3be0928132 100644 (file)
--- a/drivers/iio/adc/aspeed_adc.c
+++ b/drivers/iio/adc/aspeed_adc.c
@@ -415,6 +415,7 @@ static int aspeed_adc_vref_config(struct iio_dev *indio_dev)
        }
        adc_engine_control_reg_val =
                readl(data->base + ASPEED_REG_ENGINE_CONTROL);
+       adc_engine_control_reg_val &= ~ASPEED_ADC_REF_VOLTAGE;
 
        ret = devm_regulator_get_enable_read_voltage(data->dev, "vref");
        if (ret < 0 && ret != -ENODEV)