[PATCH v3 2/2] iio: addac: stx104: Use regmap_read_poll_timeout() for conversion poll

[William Breathitt Gray <william.gray@linaro.org>]

ADC sample captures take a certain amount of time to complete after
initiated; this conversion time range can be anywhere from 5 uSec to
53.68 Seconds depending on the configuration of the Analog Input Frame
Timer register. When the conversion is in progress, the ADC Status
register CNV bit is high. Utilize regmap_read_poll_timeout() to poll
until the ADC conversion is completed (or timeout if more than 53.68
Seconds passes).

Suggested-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: William Breathitt Gray <william.gray@linaro.org>
---
 drivers/iio/addac/stx104.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/iio/addac/stx104.c b/drivers/iio/addac/stx104.c
index 17d8b8e22dc3..a804f23b5619 100644
--- a/drivers/iio/addac/stx104.c
+++ b/drivers/iio/addac/stx104.c
@@ -202,15 +202,18 @@ static int stx104_read_raw(struct iio_dev *indio_dev,
 
 		/* trigger ADC sample capture by writing to the 8-bit
 		 * Software Strobe Register and wait for completion
+		 * Range is 5 uSec to 53.68 Seconds in steps of 25 nanoseconds.
+		 * The actual Analog Input Frame Timer time interval is calculated as:
+		 * ai_time_frame_ns = ( AIFT + 1 ) * ( 25 nSec ).
+		 * Where 0 <= AIFT <= 2147483648.
 		 */
 		err = regmap_write(priv->aio_ctl_map, STX104_SOFTWARE_STROBE, 0);
 		if (err)
 			return err;
-		do {
-			err = regmap_read(priv->aio_ctl_map, STX104_ADC_STATUS, &adc_status);
-			if (err)
-				return err;
-		} while (u8_get_bits(adc_status, STX104_CNV));
+		err = regmap_read_poll_timeout(priv->aio_ctl_map, STX104_ADC_STATUS, adc_status,
+					       !u8_get_bits(adc_status, STX104_CNV), 0, 53687092);
+		if (err)
+			return err;
 
 		err = regmap_read(priv->aio_data_map, STX104_ADC_DATA, &value);
 		if (err)
-- 
2.39.2