iio: adc: ad7124: fix chip ID mismatch

commit 96f9ab0 upstream.

The ad7124_soft_reset() function has the assumption that the chip will
assert the "power-on reset" bit in the STATUS register after a software
reset without any delay. The POR bit =0 is used to check if the chip
initialization is done.

A chip ID mismatch probe error appears intermittently when the probe
continues too soon and the ID register does not contain the expected
value.

Fix by adding a 200us delay after the software reset command is issued.

Fixes: b3af341 ("iio: adc: Add ad7124 support")
Signed-off-by: Dumitru Ceclan <[email protected]>
Reviewed-by: Nuno Sa <[email protected]>
Link: https://patch.msgid.link/[email protected]
Cc: <[email protected]>
Signed-off-by: Jonathan Cameron <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

drivers/iio/adc/ad7124.c

@@ -766,6 +766,7 @@ static int ad7124_soft_reset(struct ad7124_state *st)
 	if (ret < 0)
 		return ret;
 
+	fsleep(200);
 	timeout = 100;
 	do {
 		ret = ad_sd_read_reg(&st->sd, AD7124_STATUS, 1, &readval);