Currently ACPI-driven alarms are not cleared when they wake the
system. As consequence, expired alarms must be manually cleared to
program a new alarm. Fix this by correctly handling ACPI-driven
alarms.

More specifically, the ACPI specification [1] provides for two
alternative implementations of the RTC. Depending on the
implementation, the driver either clear the alarm from the resume
callback or from ACPI interrupt handler:

 - The platform has the RTC wakeup status fixed in hardware
   (ACPI_FADT_FIXED_RTC is 0). In this case the driver can determine
   if the RTC was the reason of the wakeup from the resume callback
   by reading the RTC status register.

 - The platform has no fixed hardware feature event bits. In this
   case a GPE is used to wake the system and the driver clears the
   alarm from its handler.

[1] http://www.acpi.info/DOWNLOADS/ACPI_5_Errata%20A.pdf

Signed-off-by: Gabriele Mazzotta <gabriele....@gmail.com>
---
 drivers/rtc/rtc-cmos.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index 1dec52f..fd7ec0a 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -900,6 +900,9 @@ static inline int cmos_poweroff(struct device *dev)
 
 #ifdef CONFIG_PM_SLEEP
 
+static void cmos_check_acpi_rtc_status(struct device *dev,
+                                      unsigned char *rtc_control);
+
 static int cmos_resume(struct device *dev)
 {
        struct cmos_rtc *cmos = dev_get_drvdata(dev);
@@ -939,6 +942,9 @@ static int cmos_resume(struct device *dev)
                        tmp &= ~RTC_AIE;
                        hpet_mask_rtc_irq_bit(RTC_AIE);
                } while (mask & RTC_AIE);
+
+               if (tmp & RTC_AIE)
+                       cmos_check_acpi_rtc_status(dev, &tmp);
        }
        spin_unlock_irq(&rtc_lock);
 
@@ -976,6 +982,22 @@ static SIMPLE_DEV_PM_OPS(cmos_pm_ops, cmos_suspend, 
cmos_resume);
 static u32 rtc_handler(void *context)
 {
        struct device *dev = context;
+       struct cmos_rtc *cmos = dev_get_drvdata(dev);
+       unsigned char rtc_control;
+       unsigned char rtc_intr;
+
+       spin_lock_irq(&rtc_lock);
+       if (!cmos_rtc.suspend_ctrl)
+               rtc_control = cmos_rtc.suspend_ctrl;
+       else
+               rtc_control = CMOS_READ(RTC_CONTROL);
+       if (rtc_control & RTC_AIE) {
+               cmos_rtc.suspend_ctrl &= ~RTC_AIE;
+               CMOS_WRITE(rtc_control, RTC_CONTROL);
+               rtc_intr = CMOS_READ(RTC_INTR_FLAGS);
+               rtc_update_irq(cmos->rtc, 1, rtc_intr);
+       }
+       spin_unlock_irq(&rtc_lock);
 
        pm_wakeup_event(dev, 0);
        acpi_clear_event(ACPI_EVENT_RTC);
@@ -1042,12 +1064,39 @@ static void cmos_wake_setup(struct device *dev)
        device_init_wakeup(dev, 1);
 }
 
+static void cmos_check_acpi_rtc_status(struct device *dev,
+                                      unsigned char *rtc_control)
+{
+       struct cmos_rtc *cmos = dev_get_drvdata(dev);
+       acpi_event_status rtc_status;
+       acpi_status status;
+
+       if (acpi_gbl_FADT.flags & ACPI_FADT_FIXED_RTC)
+               return;
+
+       status = acpi_get_event_status(ACPI_EVENT_RTC, &rtc_status);
+       if (ACPI_FAILURE(status)) {
+               dev_err(dev, "Could not get RTC status\n");
+       } else if (rtc_status & ACPI_EVENT_FLAG_SET) {
+               unsigned char mask;
+               *rtc_control &= ~RTC_AIE;
+               CMOS_WRITE(*rtc_control, RTC_CONTROL);
+               mask = CMOS_READ(RTC_INTR_FLAGS);
+               rtc_update_irq(cmos->rtc, 1, mask);
+       }
+}
+
 #else
 
 static void cmos_wake_setup(struct device *dev)
 {
 }
 
+static void cmos_check_acpi_rtc_status(struct device *dev,
+                                      unsigned char *rtc_control)
+{
+}
+
 #endif
 
 #ifdef CONFIG_PNP
-- 
2.9.3

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