iio: sx9324: Add precharge internal resistance setting

Add ability to set the precharge internal resistance from the device
tree.
Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/20220429220144.1476049-5-gwendal@chromium.orgSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/proximity/sx9324.c

@@ -72,6 +72,7 @@
 #define SX9324_REG_AFE_CTRL8		0x2c
 #define SX9324_REG_AFE_CTRL8_RESERVED	0x10
 #define SX9324_REG_AFE_CTRL8_RESFILTIN_4KOHM 0x02
+#define SX9324_REG_AFE_CTRL8_RESFILTIN_MASK GENMASK(3, 0)
 #define SX9324_REG_AFE_CTRL9		0x2d
 #define SX9324_REG_AFE_CTRL9_AGAIN_1	0x08
 
@@ -909,6 +910,18 @@ sx9324_get_default_reg(struct device *dev, int idx,
 		reg_def->def |= FIELD_PREP(SX9324_REG_AFE_CTRL4_RESOLUTION_MASK,
 					   raw);
 		break;
+	case SX9324_REG_AFE_CTRL8:
+		ret = device_property_read_u32(dev,
+				"semtech,input-precharge-resistor-ohms",
+				&raw);
+		if (ret)
+			break;
+
+		reg_def->def &= ~SX9324_REG_AFE_CTRL8_RESFILTIN_MASK;
+		reg_def->def |= FIELD_PREP(SX9324_REG_AFE_CTRL8_RESFILTIN_MASK,
+					   raw / 2000);
+		break;
+
 	case SX9324_REG_ADV_CTRL5:
 		ret = device_property_read_u32(dev, "semtech,startup-sensor",
 					       &start);