iio: sx9360: Add pre-charge resistor 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/20220429220144.1476049-11-gwendal@chromium.orgSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/proximity/sx9360.c

@@ -51,6 +51,8 @@
 #define SX9360_REG_GNRL_REG_2_FREQ(_r)  (SX9360_FOSC_HZ / ((_r) * 8192))
 
 #define SX9360_REG_AFE_CTRL1		0x21
+#define SX9360_REG_AFE_CTRL1_RESFILTIN_MASK GENMASK(3, 0)
+#define SX9360_REG_AFE_CTRL1_RESFILTIN_0OHMS 0
 #define SX9360_REG_AFE_PARAM0_PHR	0x22
 #define SX9360_REG_AFE_PARAM1_PHR	0x23
 #define SX9360_REG_AFE_PARAM0_PHM	0x24
@@ -671,7 +673,7 @@ static const struct sx_common_reg_default sx9360_default_regs[] = {
 	{ SX9360_REG_GNRL_CTRL1, 0x00 },
 	{ SX9360_REG_GNRL_CTRL2, SX9360_REG_GNRL_CTRL2_PERIOD_102MS },
 
-	{ SX9360_REG_AFE_CTRL1, 0x00 },
+	{ SX9360_REG_AFE_CTRL1, SX9360_REG_AFE_CTRL1_RESFILTIN_0OHMS },
 	{ SX9360_REG_AFE_PARAM0_PHR, SX9360_REG_AFE_PARAM0_RSVD |
 		SX9360_REG_AFE_PARAM0_RESOLUTION_128 },
 	{ SX9360_REG_AFE_PARAM1_PHR, SX9360_REG_AFE_PARAM1_AGAIN_PHM_6PF |
@@ -722,6 +724,17 @@ sx9360_get_default_reg(struct device *dev, int idx,
 
 	memcpy(reg_def, &sx9360_default_regs[idx], sizeof(*reg_def));
 	switch (reg_def->reg) {
+	case SX9360_REG_AFE_CTRL1:
+		ret = device_property_read_u32(dev,
+				"semtech,input-precharge-resistor-ohms",
+				&raw);
+		if (ret)
+			break;
+
+		reg_def->def &= ~SX9360_REG_AFE_CTRL1_RESFILTIN_MASK;
+		reg_def->def |= FIELD_PREP(SX9360_REG_AFE_CTRL1_RESFILTIN_MASK,
+					   raw / 2000);
+		break;
 	case SX9360_REG_AFE_PARAM0_PHR:
 	case SX9360_REG_AFE_PARAM0_PHM:
 		ret = device_property_read_u32(dev, "semtech,resolution", &raw);