[PATCH] iio: proximity: sx9310: fix semtech,proxraw-strength = <0>

[Arnav Kapoor <kapoorarnav43@gmail.com>]

The binding allows semtech,proxraw-strength values of 0, 2, 4 and 8,
where 0 turns the PROXRAW filter off and the others select a strength of
1 - 1/N, i.e. register codes 1 to 3.

sx9310_get_default_reg() converts the property with ilog2(raw). For 0,
ilog2() returns -1, which FIELD_PREP() masks to 3 in the 2-bit RAWFILT
field. A board that asks for the filter to be off therefore gets the
strongest filter, the same as semtech,proxraw-strength = <8>.

Keep 0 as register code 0.

Fixes: 5b19ca2c78a0 ("iio: sx9310: Set various settings from DT")
Signed-off-by: Arnav Kapoor <kapoorarnav43@gmail.com>
---
No in-tree DT uses semtech,proxraw-strength = <0> (sc7180-trogdor-lazor
uses 8), so this only affects out-of-tree boards. I checked the
mapping with a userspace copy of the ilog2()/FIELD_PREP() conversion:
0 and 8 both give RAWFILT = 3 before this patch, 0 gives 0 after it.

Compile-tested only (W=1); I don't have SX9310 hardware.

 drivers/iio/proximity/sx9310.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/proximity/sx9310.c b/drivers/iio/proximity/sx9310.c
index 2585b9c6fb69..a39277237d39 100644
--- a/drivers/iio/proximity/sx9310.c
+++ b/drivers/iio/proximity/sx9310.c
@@ -855,7 +855,8 @@ sx9310_get_default_reg(struct device *dev, int idx,
 		if (ret) {
 			raw = FIELD_GET(SX9310_REG_PROX_CTRL5_RAWFILT_MASK,
 					reg_def->def);
-		} else {
+		} else if (raw) {
+			/* 0 means off; 2, 4 and 8 are codes 1 to 3. */
 			raw = ilog2(raw);
 		}
 

base-commit: 340d44bdf9db0f095f99845b5ad8628781d79b6f
-- 
2.53.0