iio: adc: stm32-adc: make safe adc disable

From ADC reference manual the software is allowed to write the
control bit ADDIS of the ADC_CR register only if the ADC is enabled.
Return immediately from stm32h7_adc_disable() if ADC is already disabled.

Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
Reviewed-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Link: https://lore.kernel.org/r/20220620154738.801706-2-olivier.moysan@foss.st.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
index a68ecbd..80e333f 100644 (file)
--- a/drivers/iio/adc/stm32-adc.c
+++ b/drivers/iio/adc/stm32-adc.c
@@ -876,6 +876,9 @@ static void stm32h7_adc_disable(struct iio_dev *indio_dev)
        int ret;
        u32 val;
 
+       if (!(stm32_adc_readl(adc, STM32H7_ADC_CR) & STM32H7_ADEN))
+               return;
+
        /* Disable ADC and wait until it's effectively disabled */
        stm32_adc_set_bits(adc, STM32H7_ADC_CR, STM32H7_ADDIS);
        ret = stm32_adc_readl_poll_timeout(STM32H7_ADC_CR, val,