[PATCH] iio: dac: ad9739a: write complete MU_CNT1 register during lock

[Nuno Sa <nuno.sa@analog.com>]

As specified by the datasheet we should write the value 0x3 (enable
plus tracking gain) into the MU_CNT1 register during the MU lock phase.

Currently we were only setting the enable bit (bit 0) as the tracking
gain default value is already set to 1. While we should be mostly fine
in assuming the tracking gain will have the value it should, better to
explicitly write it. On top of that the datasheet also states to
re-attempt the writes in case the lock fails which we were not doing for
the tracking gain bit.

Lastly, the recommended value for the MU phase slope lock (bit 6) is 0
but for some reason the default value is 1 and hence, we were not
changing it accordingly.

Note there was no problem with the MU lock mechanism so this is not
being treated as a fix but rather an improvement.

Signed-off-by: Nuno Sa <nuno.sa@analog.com>
---
 drivers/iio/dac/ad9739a.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/dac/ad9739a.c b/drivers/iio/dac/ad9739a.c
index ff33120075bf..f56eabe53723 100644
--- a/drivers/iio/dac/ad9739a.c
+++ b/drivers/iio/dac/ad9739a.c
@@ -45,6 +45,7 @@
 #define AD9739A_REG_MU_DUTY		0x25
 #define AD9739A_REG_MU_CNT1		0x26
 #define   AD9739A_MU_EN_MASK		BIT(0)
+#define   AD9739A_MU_GAIN_MASK		BIT(1)
 #define AD9739A_REG_MU_CNT2		0x27
 #define AD9739A_REG_MU_CNT3		0x28
 #define AD9739A_REG_MU_CNT4		0x29
@@ -220,8 +221,8 @@ static int ad9739a_init(struct device *dev, const struct ad9739a_state *st)
 			return ret;
 
 		/* Enable the Mu controller search and track mode. */
-		ret = regmap_set_bits(st->regmap, AD9739A_REG_MU_CNT1,
-				      AD9739A_MU_EN_MASK);
+		ret = regmap_write(st->regmap, AD9739A_REG_MU_CNT1,
+				   AD9739A_MU_EN_MASK | AD9739A_MU_GAIN_MASK);
 		if (ret)
 			return ret;
 

---
base-commit: b22457f6c572c1b453207d13613a4e476d3dd0fb
change-id: 20240429-ad9739a-improv-adeda16e0dd5
--

Thanks!
- Nuno Sá