[PATCH v2 1/3] rtc: ds1685: arm the wake-up alarm at power-off only if an alarm is set

[Imre Kaloz <kaloz@kernel.org>]

ds1685_rtc_poweroff() always sets WIE. The wake-up alarm then compares
the time-of-day and date alarm registers, which hold whatever was last
written to them, and a match powers the machine straight back on.

Set WIE only when AIE is set in Control B, and clear it otherwise.

Fixes: aaaf5fbf56f1 ("rtc: add driver for DS1685 family of real time clocks")
Signed-off-by: Imre Kaloz <kaloz@kernel.org>
---
 drivers/rtc/rtc-ds1685.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/drivers/rtc/rtc-ds1685.c b/drivers/rtc/rtc-ds1685.c
index 5fc8e36b1abf..94c89333c5d5 100644
--- a/drivers/rtc/rtc-ds1685.c
+++ b/drivers/rtc/rtc-ds1685.c
@@ -1367,7 +1367,7 @@ module_platform_driver(ds1685_rtc_driver);
 void __noreturn
 ds1685_rtc_poweroff(struct platform_device *pdev)
 {
-	u8 ctrla, ctrl4a, ctrl4b;
+	u8 ctrla, ctrlb, ctrl4a, ctrl4b;
 	struct ds1685_priv *rtc;
 
 	/* Check for valid RTC data, else, spin forever. */
@@ -1394,6 +1394,8 @@ ds1685_rtc_poweroff(struct platform_device *pdev)
 		ctrla &= ~(RTC_CTRL_A_DV2);
 		rtc->write(rtc, RTC_CTRL_A, ctrla);
 
+		ctrlb = rtc->read(rtc, RTC_CTRL_B);
+
 		/*
 		 * Read Control 4A and check the status of the auxillary
 		 * battery.  This must be present and working (VRT2 = 1)
@@ -1408,13 +1410,17 @@ ds1685_rtc_poweroff(struct platform_device *pdev)
 
 			/*
 			 * The auxillary battery is present and working.
-			 * Enable extended functions (ABE=1), enable
-			 * wake-up (WIE=1), and enable kickstart (KSE=1)
-			 * in Control 4B.
+			 * Enable extended functions (ABE=1) and kickstart
+			 * (KSE=1) in Control 4B.  Enable wake-up (WIE=1) only
+			 * if an alarm is set, else stale alarm registers
+			 * can power the system back on.
 			 */
 			ctrl4b = rtc->read(rtc, RTC_EXT_CTRL_4B);
-			ctrl4b |= (RTC_CTRL_4B_ABE | RTC_CTRL_4B_WIE |
-				   RTC_CTRL_4B_KSE);
+			ctrl4b |= (RTC_CTRL_4B_ABE | RTC_CTRL_4B_KSE);
+			if (ctrlb & RTC_CTRL_B_AIE)
+				ctrl4b |= RTC_CTRL_4B_WIE;
+			else
+				ctrl4b &= ~(RTC_CTRL_4B_WIE);
 			rtc->write(rtc, RTC_EXT_CTRL_4B, ctrl4b);
 		}
 
-- 
2.47.3