[PATCH] rtc: mt6397: Add BBPU alarm status reset and shutdown handling

[mtk34418 <dhatrisri.anumula@mediatek.com>]

From: Shunxi Zhang <ot_shunxi.zhang@mediatek.com>

This patch introduces a new function, mtk_rtc_reset_bbpu_alarm_status,
to reset the BBPU alarm status in the MT6397 RTC driver. This function
writes the necessary bits to the RTC_BBPU register to clear the alarm
status and ensure proper operation.

Additionally, the mtk_rtc_shutdown function is added to handle RTC
shutdown events. It resets the BBPU alarm status and updates the
RTC_IRQ_EN register to disable the one-shot alarm interrupt,
ensuring a clean shutdown process.

Signed-off-by: Shunxi Zhang <ot_shunxi.zhang@mediatek.com>
Signed-off-by: Dhatrisri Anumula <dhatrisri.anumula@mediatek.com>
---

diff --git a/drivers/rtc/rtc-mt6397.c b/drivers/rtc/rtc-mt6397.c
index 692c00f..063bd39 100644
--- a/drivers/rtc/rtc-mt6397.c
+++ b/drivers/rtc/rtc-mt6397.c
@@ -37,6 +37,21 @@ static int mtk_rtc_write_trigger(struct mt6397_rtc *rtc)
 	return ret;
 }
 
+static void mtk_rtc_reset_bbpu_alarm_status(struct mt6397_rtc *rtc)
+{
+	u32 bbpu = RTC_BBPU_KEY | RTC_BBPU_PWREN | RTC_BBPU_RESET_AL;
+	int ret;
+
+	ret = regmap_write(rtc->regmap, rtc->addr_base + RTC_BBPU, bbpu);
+	if (ret < 0) {
+		dev_err(rtc->rtc_dev->dev.parent, "%s: write rtc bbpu error\n",
+			__func__);
+		return;
+	}
+
+	mtk_rtc_write_trigger(rtc);
+}
+
 static irqreturn_t mtk_rtc_irq_handler_thread(int irq, void *data)
 {
 	struct mt6397_rtc *rtc = data;
@@ -51,6 +66,8 @@ static irqreturn_t mtk_rtc_irq_handler_thread(int irq, void *data)
 		if (regmap_write(rtc->regmap, rtc->addr_base + RTC_IRQ_EN,
 				 irqen) == 0)
 			mtk_rtc_write_trigger(rtc);
+
+		mtk_rtc_reset_bbpu_alarm_status(rtc);
 		mutex_unlock(&rtc->lock);
 
 		return IRQ_HANDLED;
@@ -297,6 +314,22 @@ static int mtk_rtc_probe(struct platform_device *pdev)
 	return devm_rtc_register_device(rtc->rtc_dev);
 }
 
+static void mtk_rtc_shutdown(struct platform_device *pdev)
+{
+	struct mt6397_rtc *rtc = platform_get_drvdata(pdev);
+	int ret = 0;
+
+	mtk_rtc_reset_bbpu_alarm_status(rtc);
+
+	ret = regmap_update_bits(rtc->regmap,
+				 rtc->addr_base + RTC_IRQ_EN,
+				 RTC_IRQ_EN_ONESHOT_AL, 0);
+	if (ret < 0)
+		return;
+
+	mtk_rtc_write_trigger(rtc);
+}
+
 #ifdef CONFIG_PM_SLEEP
 static int mt6397_rtc_suspend(struct device *dev)
 {
@@ -345,7 +378,8 @@ static struct platform_driver mtk_rtc_driver = {
 		.of_match_table = mt6397_rtc_of_match,
 		.pm = &mt6397_pm_ops,
 	},
-	.probe	= mtk_rtc_probe,
+	.probe = mtk_rtc_probe,
+	.shutdown = mtk_rtc_shutdown,
 };
 
 module_platform_driver(mtk_rtc_driver);