iio: adc: at91-sama5d2_adc: disable/prepare buffer on suspend/resume

In case triggered buffers are enabled while system is suspended they will
not work anymore after resume. For this call at91_adc_buffer_postdisable()
on suspend and at91_adc_buffer_prepare() on resume. On tests it has been
seen that at91_adc_buffer_postdisable() call is not necessary but it has
been kept because it also does the book keeping for DMA. On resume path
there is no need to call at91_adc_configure_touch() as it is embedded in
at91_adc_buffer_prepare().

Fixes: 073c6620 ("iio: adc: at91-sama5d2_adc: add support for DMA")
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20220803102855.2191070-5-claudiu.beznea@microchip.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/at91-sama5d2_adc.c

@@ -2116,6 +2116,9 @@ static int at91_adc_suspend(struct device *dev)
 	struct iio_dev *indio_dev = dev_get_drvdata(dev);
 	struct at91_adc_state *st = iio_priv(indio_dev);
 
+	if (iio_buffer_enabled(indio_dev))
+		at91_adc_buffer_postdisable(indio_dev);
+
 	/*
 	 * Do a sofware reset of the ADC before we go to suspend.
 	 * this will ensure that all pins are free from being muxed by the ADC
@@ -2159,14 +2162,11 @@ static int at91_adc_resume(struct device *dev)
 	if (!iio_buffer_enabled(indio_dev))
 		return 0;
 
-	/* check if we are enabling triggered buffer or the touchscreen */
-	if (at91_adc_current_chan_is_touch(indio_dev))
-		return at91_adc_configure_touch(st, true);
-	else
-		return at91_adc_configure_trigger(st->trig, true);
+	ret = at91_adc_buffer_prepare(indio_dev);
+	if (ret)
+		goto vref_disable_resume;
 
-	/* not needed but more explicit */
-	return 0;
+	return at91_adc_configure_trigger(st->trig, true);
 
 vref_disable_resume:
 	regulator_disable(st->vref);