[PATCH] rtc: ti-k3: Add support to resume from IO DDR low power mode

[Akashdeep Kaur <a-kaur@ti.com>]

During IO DDR low power mode, the RTC IP is reset and loses its
register configuration. The DDR memory still preserves all driver states
(reference counts, software context). System clocks are saved and restored
by Device Manager (DM) firmware during the resume sequence.
Add support to reconfigure the RTC IP registers in resume handler only if
resume hook is called during IO DDR low power mode resume.

Signed-off-by: Akashdeep Kaur <a-kaur@ti.com>
---

Tested deep sleep with rtcwake after IO DDR resume on AM62P-SK.

---
 drivers/rtc/rtc-ti-k3.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/rtc/rtc-ti-k3.c b/drivers/rtc/rtc-ti-k3.c
index ec759d8f7023..e801f5b9d757 100644
--- a/drivers/rtc/rtc-ti-k3.c
+++ b/drivers/rtc/rtc-ti-k3.c
@@ -640,10 +640,18 @@ static int __maybe_unused ti_k3_rtc_suspend(struct device *dev)
 static int __maybe_unused ti_k3_rtc_resume(struct device *dev)
 {
 	struct ti_k3_rtc *priv = dev_get_drvdata(dev);
+	int ret = 0;
+
+	if (k3rtc_check_unlocked(priv)) {
+		/* RTC locked implies low power mode exit where RTC loses context */
+		ret = k3rtc_configure(dev);
+		if (ret)
+			return ret;
+	}
 
 	if (device_may_wakeup(dev))
 		disable_irq_wake(priv->irq);
-	return 0;
+	return ret;
 }
 
 static SIMPLE_DEV_PM_OPS(ti_k3_rtc_pm_ops, ti_k3_rtc_suspend, ti_k3_rtc_resume);
-- 
2.34.1