iio: adc: at91_adc: correct default shtim value

When sample_hold_time is zero (this is the case when DT is not used or if
atmel,adc-sample-hold-time is omitted), then the calculated shtim is large.

Make that 0, which is the default for that register and the ADC will then use a
sane value of 2/ADCCLK or 1/ADCCLK depending on the version.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Josh Wu <josh.wu@atmel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 5 insertions, 2 deletions

diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c
index bbba014c9939..89777ed9abd8 100644
--- a/drivers/iio/adc/at91_adc.c
+++ b/drivers/iio/adc/at91_adc.c
@@ -1007,8 +1007,11 @@ static int at91_adc_probe(struct platform_device *pdev)
          * the best converted final value between two channels selection
          * The formula thus is : Sample and Hold Time = (shtim + 1) / ADCClock
          */
-        shtim = round_up((st->sample_hold_time * adc_clk_khz /
-                          1000) - 1, 1);
+        if (st->sample_hold_time > 0)
+                shtim = round_up((st->sample_hold_time * adc_clk_khz / 1000)
+                                 - 1, 1);
+        else
+                shtim = 0;
 
         reg = AT91_ADC_PRESCAL_(prsc) & st->registers->mr_prescal_mask;
         reg |= AT91_ADC_STARTUP_(ticks) & st->registers->mr_startup_mask;