[PATCH v3] iio: sx9310: Fix semtech,avg-pos-strength setting when > 16

[Stephen Boyd <swboyd@chromium.org>]

This DT property can be 0, 16, and then 64, but not 32. The math here
doesn't recognize this slight bump in the power of 2 numbers and
translates a DT property of 64 into the register value '3' when it
really should be '2'. Fix it by subtracting one more if the number being
translated is larger than 31. Also use clamp() because we're here.

Cc: Daniel Campello <campello@chromium.org>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Peter Meerwald-Stadler <pmeerw@pmeerw.net>
Cc: Douglas Anderson <dianders@chromium.org>
Cc: Gwendal Grignou <gwendal@chromium.org>
Cc: Evan Green <evgreen@chromium.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
---

Changes from v2 (https://lore.kernel.org/r/20201120182944.543428-1-swboyd@chromium.org):                                                                                                         
 * Use clamp()
 * Add comment to clarify

Changes from v1 (https://lore.kernel.org/r/20201120073842.3232458-1-swboyd@chromium.org):                                                                                                         
 * Changed ternary to consider 17 to 31 as the same as 16   

 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 a2f820997afc..0e6863e4d384 100644
--- a/drivers/iio/proximity/sx9310.c
+++ b/drivers/iio/proximity/sx9310.c
@@ -1305,7 +1305,8 @@ sx9310_get_default_reg(struct sx9310_data *data, int i,
 		if (ret)
 			break;
 
-		pos = min(max(ilog2(pos), 3), 10) - 3;
+		/* Powers of 2, except for a gap between 16 and 64 */
+		pos = clamp(ilog2(pos), 3, 11) - (pos >= 32 ? 4 : 3);
 		reg_def->def &= ~SX9310_REG_PROX_CTRL7_AVGPOSFILT_MASK;
 		reg_def->def |= FIELD_PREP(SX9310_REG_PROX_CTRL7_AVGPOSFILT_MASK,
 					   pos);

base-commit: 5b19ca2c78a0838976064c0347e46a2c859b541d
-- 
https://chromeos.dev