Add a validation check for the sampling frequency value before using it
as a divisor. A user writing zero or a negative value to the
sampling_frequency sysfs attribute triggers a division by zero in the
kernel.

Also prevent unsigned integer underflow when the computed cycle count is
smaller than NXP_SAR_ADC_CONV_TIME, which would wrap the u32 inpsamp to
a huge value.

Fixes: fdee77dea4b6 ("iio: adc: Add the NXP SAR ADC support for the s32g2/3 platforms")
Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
---
 drivers/iio/adc/nxp-sar-adc.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/adc/nxp-sar-adc.c b/drivers/iio/adc/nxp-sar-adc.c
index a6e4888a8464..c611f1c612e6 100644
--- a/drivers/iio/adc/nxp-sar-adc.c
+++ b/drivers/iio/adc/nxp-sar-adc.c
@@ -560,6 +560,9 @@ static int nxp_sar_adc_write_raw(struct iio_dev *indio_dev, struct iio_chan_spec
 
 	switch (mask) {
 	case IIO_CHAN_INFO_SAMP_FREQ:
+		if (val <= 0)
+			return -EINVAL;
+
 		/*
 		 * Configures the sample period duration in terms of the SAR
 		 * controller clock. The minimum acceptable value is 8.
@@ -568,7 +571,11 @@ static int nxp_sar_adc_write_raw(struct iio_dev *indio_dev, struct iio_chan_spec
 		 * sampling timing which gives us the number of cycles expected.
 		 * The value is 8-bit wide, consequently the max value is 0xFF.
 		 */
-		inpsamp = clk_get_rate(info->clk) / val - NXP_SAR_ADC_CONV_TIME;
+		inpsamp = clk_get_rate(info->clk) / val;
+		if (inpsamp < NXP_SAR_ADC_CONV_TIME)
+			return -EINVAL;
+
+		inpsamp -= NXP_SAR_ADC_CONV_TIME;
 		nxp_sar_adc_conversion_timing_set(info, inpsamp);
 		return 0;
 
-- 
2.43.0