rtc: s5m: replace open-coded read/modify/write registers with regmap helpers

Instead of the open-coded read/modify/write sequence, we can simply use
the regmap helpers regmap_set_bits() and regmap_update_bits()
respectively.

This makes the code easier to read, and avoids extra work in case the
underlying bus supports updating bits via
struct regmap_bus::reg_update_bits() directly (which is the case for
S2MPG10 on gs101 where this driver communicates via ACPM).

Signed-off-by: André Draszik <andre.draszik@linaro.org>
Link: https://lore.kernel.org/r/20250409-s2mpg10-v4-31-d66d5f39b6bf@linaro.org
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Author: andred

drivers/rtc/rtc-s5m.c

@@ -279,17 +279,9 @@ static int s5m_check_pending_alarm_interrupt(struct s5m_rtc_info *info,
 static int s5m8767_rtc_set_time_reg(struct s5m_rtc_info *info)
 {
 	int ret;
-	unsigned int data;
-
-	ret = regmap_read(info->regmap, info->regs->udr_update, &data);
-	if (ret < 0) {
-		dev_err(info->dev, "failed to read update reg(%d)\n", ret);
-		return ret;
-	}
-
-	data |= info->regs->write_time_udr_mask;
 
-	ret = regmap_write(info->regmap, info->regs->udr_update, data);
+	ret = regmap_set_bits(info->regmap, info->regs->udr_update,
+			      info->regs->write_time_udr_mask);
 	if (ret < 0) {
 		dev_err(info->dev, "failed to write update reg(%d)\n", ret);
 		return ret;
@@ -303,19 +295,12 @@ static int s5m8767_rtc_set_time_reg(struct s5m_rtc_info *info)
 static int s5m8767_rtc_set_alarm_reg(struct s5m_rtc_info *info)
 {
 	int ret;
-	unsigned int data;
-
-	ret = regmap_read(info->regmap, info->regs->udr_update, &data);
-	if (ret < 0) {
-		dev_err(info->dev, "%s: fail to read update reg(%d)\n",
-			__func__, ret);
-		return ret;
-	}
+	unsigned int udr_mask;
 
-	data |= info->regs->write_alarm_udr_mask;
+	udr_mask = info->regs->write_alarm_udr_mask;
 	switch (info->device_type) {
 	case S5M8767X:
-		data &= ~S5M_RTC_TIME_EN_MASK;
+		udr_mask |= S5M_RTC_TIME_EN_MASK;
 		break;
 	case S2MPG10:
 	case S2MPS15X:
@@ -327,7 +312,8 @@ static int s5m8767_rtc_set_alarm_reg(struct s5m_rtc_info *info)
 		return -EINVAL;
 	}
 
-	ret = regmap_write(info->regmap, info->regs->udr_update, data);
+	ret = regmap_update_bits(info->regmap, info->regs->udr_update,
+				 udr_mask, info->regs->write_alarm_udr_mask);
 	if (ret < 0) {
 		dev_err(info->dev, "%s: fail to write update reg(%d)\n",
 			__func__, ret);