[PATCH] rtc: cmos: Fix accidentally enabling rtc channel

[PATCH] rtc: cmos: Fix accidentally enabling rtc channel

[Derek Basehore]

During resume, we call hpet_rtc_timer_init after masking an irq bit in hpet.
This will cause the call to hpet_disable_rtc_channel to be undone if RTC_AIE is
the only bit not masked.

Signed-off-by: Derek Basehore <dbasehore@chromium.org>
---
 drivers/rtc/rtc-cmos.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index cc5bea9..ee0bc69 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -854,6 +854,10 @@ static int cmos_resume(struct device *dev)
 		}
 
 		spin_lock_irq(&rtc_lock);
+		if (device_may_wakeup(dev)) {
+			hpet_rtc_timer_init();
+		}
+
 		do {
 			CMOS_WRITE(tmp, RTC_CONTROL);
 			hpet_set_rtc_irq_bit(tmp & RTC_IRQMASK);
@@ -869,7 +873,6 @@ static int cmos_resume(struct device *dev)
 			rtc_update_irq(cmos->rtc, 1, mask);
 			tmp &= ~RTC_AIE;
 			hpet_mask_rtc_irq_bit(RTC_AIE);
-			hpet_rtc_timer_init();
 		} while (mask & RTC_AIE);
 		spin_unlock_irq(&rtc_lock);
 	}
-- 
1.8.2.1

Re: [PATCH] rtc: cmos: Fix accidentally enabling rtc channel

[Andrew Morton]

On Wed, 22 May 2013 18:04:05 -0700 Derek Basehore <dbasehore@chromium.org> wrote:

> During resume, we call hpet_rtc_timer_init after masking an irq bit in hpet.
> This will cause the call to hpet_disable_rtc_channel to be undone if RTC_AIE is
> the only bit not masked.

What were the user-visible runtime effects of this bug?

Re: [PATCH] rtc: cmos: Fix accidentally enabling rtc channel

[dbasehore .]

I'm still debugging all of the issues, but allowing the cmos interrupt
handler to run before resuming caused some issues where the timer for
the alarm was not removed. This would cause other, later timers to not
be cleared, so utilities such as hwclock would time out when waiting
for the update interrupt.

There's another patch needed that I am currently testing that works
around an issue seen in coreboot (and probably other firmware) where
the RTC_CONTROL register is cleared before we get to the kernel. This
prevents the cmos interrupt handler from clearing an alarm.

On Wed, May 29, 2013 at 12:27 PM, Andrew Morton
<akpm@linux-foundation.org> wrote:
> On Wed, 22 May 2013 18:04:05 -0700 Derek Basehore <dbasehore@chromium.org> wrote:
>
>> During resume, we call hpet_rtc_timer_init after masking an irq bit in hpet.
>> This will cause the call to hpet_disable_rtc_channel to be undone if RTC_AIE is
>> the only bit not masked.
>
> What were the user-visible runtime effects of this bug?

[PATCH] rtc: cmos: Workaround bios clearing rtc control

[Derek Basehore]

The bios may clear the rtc control register when resuming the system. Since the
cmos interrupt handler may now be run before the rtc_cmos is resumed, this can
cause the interrupt handler to ignore an alarm since the alarm bit is not set in
the rtc control register. To work around this, check if the rtc_cmos is
suspended and use the stored value for the rtc control register.

Signed-off-by: Derek Basehore <dbasehore@chromium.org>
Reviewed-by: Sameer Nanda <snanda@chromium.org>
---
 drivers/rtc/rtc-cmos.c | 35 ++++++++++++++++++++++-------------
 1 file changed, 22 insertions(+), 13 deletions(-)

diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index ee0bc69..22803fe 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -556,17 +556,24 @@ static irqreturn_t cmos_interrupt(int irq, void *p)
 	rtc_control = CMOS_READ(RTC_CONTROL);
 	if (is_hpet_enabled())
 		irqstat = (unsigned long)irq & 0xF0;
-	irqstat &= (rtc_control & RTC_IRQMASK) | RTC_IRQF;
+
+	/* If we were suspended, RTC_CONTROL may not be accurate since the
+	 * bios may have cleared it.
+	 */
+	if (!cmos_rtc.suspend_ctrl)
+		irqstat &= (rtc_control & RTC_IRQMASK) | RTC_IRQF;
+	else
+		irqstat &= (cmos_rtc.suspend_ctrl & RTC_IRQMASK) | RTC_IRQF;
 
 	/* All Linux RTC alarms should be treated as if they were oneshot.
 	 * Similar code may be needed in system wakeup paths, in case the
 	 * alarm woke the system.
 	 */
 	if (irqstat & RTC_AIE) {
+		cmos_rtc.suspend_ctrl &= ~RTC_AIE;
 		rtc_control &= ~RTC_AIE;
 		CMOS_WRITE(rtc_control, RTC_CONTROL);
 		hpet_mask_rtc_irq_bit(RTC_AIE);
-
 		CMOS_READ(RTC_INTR_FLAGS);
 	}
 	spin_unlock(&rtc_lock);
@@ -839,21 +846,23 @@ static inline int cmos_poweroff(struct device *dev)
 static int cmos_resume(struct device *dev)
 {
 	struct cmos_rtc	*cmos = dev_get_drvdata(dev);
-	unsigned char	tmp = cmos->suspend_ctrl;
+	unsigned char	tmp;
 
+	if (cmos->enabled_wake) {
+		if (cmos->wake_off)
+			cmos->wake_off(dev);
+		else
+			disable_irq_wake(cmos->irq);
+		cmos->enabled_wake = 0;
+	}
+
+	spin_lock_irq(&rtc_lock);
+	tmp = cmos->suspend_ctrl;
+	cmos->suspend_ctrl = 0;
 	/* re-enable any irqs previously active */
 	if (tmp & RTC_IRQMASK) {
 		unsigned char	mask;
 
-		if (cmos->enabled_wake) {
-			if (cmos->wake_off)
-				cmos->wake_off(dev);
-			else
-				disable_irq_wake(cmos->irq);
-			cmos->enabled_wake = 0;
-		}
-
-		spin_lock_irq(&rtc_lock);
 		if (device_may_wakeup(dev)) {
 			hpet_rtc_timer_init();
 		}
@@ -874,8 +883,8 @@ static int cmos_resume(struct device *dev)
 			tmp &= ~RTC_AIE;
 			hpet_mask_rtc_irq_bit(RTC_AIE);
 		} while (mask & RTC_AIE);
-		spin_unlock_irq(&rtc_lock);
 	}
+	spin_unlock_irq(&rtc_lock);
 
 	dev_dbg(dev, "resume, ctrl %02x\n", tmp);
 
-- 
1.8.2.1