rtc-cmos: avoid spurious irqs

This fixes kernel http://bugzilla.kernel.org/show_bug.cgi?id=11112 (bogus
RTC update IRQs reported) for rtc-cmos, in two ways:

  - When HPET is stealing the IRQs, use the first IRQ to grab
    the seconds counter which will be monitored (instead of
    using whatever was previously in that memory);

  - In sane IRQ handling modes, scrub out old IRQ status before
    enabling IRQs.

That latter is done by tightening up IRQ handling for rtc-cmos everywhere,
also ensuring that when HPET is used it's the only thing triggering IRQ
reports to userspace; net object shrink.

Also fix a bogus HPET message related to its RTC emulation.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Report-by: W Unruh <unruh@physics.ubc.ca>
Cc: Andrew Victor <avictor.za@gmail.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 63 insertions, 77 deletions

diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index e9984650ea95..6ea349aba3ba 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -235,11 +235,56 @@ static int cmos_read_alarm(struct device *dev, struct rtc_wkalrm *t)
         return 0;
 }
 
+static void cmos_checkintr(struct cmos_rtc *cmos, unsigned char rtc_control)
+{
+        unsigned char   rtc_intr;
+
+        /* NOTE after changing RTC_xIE bits we always read INTR_FLAGS;
+         * allegedly some older rtcs need that to handle irqs properly
+         */
+        rtc_intr = CMOS_READ(RTC_INTR_FLAGS);
+
+        if (is_hpet_enabled())
+                return;
+
+        rtc_intr &= (rtc_control & RTC_IRQMASK) | RTC_IRQF;
+        if (is_intr(rtc_intr))
+                rtc_update_irq(cmos->rtc, 1, rtc_intr);
+}
+
+static void cmos_irq_enable(struct cmos_rtc *cmos, unsigned char mask)
+{
+        unsigned char   rtc_control;
+
+        /* flush any pending IRQ status, notably for update irqs,
+         * before we enable new IRQs
+         */
+        rtc_control = CMOS_READ(RTC_CONTROL);
+        cmos_checkintr(cmos, rtc_control);
+
+        rtc_control |= mask;
+        CMOS_WRITE(rtc_control, RTC_CONTROL);
+        hpet_set_rtc_irq_bit(mask);
+
+        cmos_checkintr(cmos, rtc_control);
+}
+
+static void cmos_irq_disable(struct cmos_rtc *cmos, unsigned char mask)
+{
+        unsigned char   rtc_control;
+
+        rtc_control = CMOS_READ(RTC_CONTROL);
+        rtc_control &= ~mask;
+        CMOS_WRITE(rtc_control, RTC_CONTROL);
+        hpet_mask_rtc_irq_bit(mask);
+
+        cmos_checkintr(cmos, rtc_control);
+}
+
 static int cmos_set_alarm(struct device *dev, struct rtc_wkalrm *t)
 {
         struct cmos_rtc *cmos = dev_get_drvdata(dev);
         unsigned char   mon, mday, hrs, min, sec;
-        unsigned char   rtc_control, rtc_intr;
 
         if (!is_valid_irq(cmos->irq))
                 return -EIO;
@@ -266,15 +311,7 @@ static int cmos_set_alarm(struct device *dev, struct rtc_wkalrm *t)
         spin_lock_irq(&rtc_lock);
 
         /* next rtc irq must not be from previous alarm setting */
-        rtc_control = CMOS_READ(RTC_CONTROL);
-        rtc_control &= ~RTC_AIE;
-        CMOS_WRITE(rtc_control, RTC_CONTROL);
-        hpet_mask_rtc_irq_bit(RTC_AIE);
-
-        rtc_intr = CMOS_READ(RTC_INTR_FLAGS);
-        rtc_intr &= (rtc_control & RTC_IRQMASK) | RTC_IRQF;
-        if (is_intr(rtc_intr))
-                rtc_update_irq(cmos->rtc, 1, rtc_intr);
+        cmos_irq_disable(cmos, RTC_AIE);
 
         /* update alarm */
         CMOS_WRITE(hrs, RTC_HOURS_ALARM);
@@ -293,16 +330,8 @@ static int cmos_set_alarm(struct device *dev, struct rtc_wkalrm *t)
          */
         hpet_set_alarm_time(t->time.tm_hour, t->time.tm_min, t->time.tm_sec);
 
-        if (t->enabled) {
-                rtc_control |= RTC_AIE;
-                CMOS_WRITE(rtc_control, RTC_CONTROL);
-                hpet_set_rtc_irq_bit(RTC_AIE);
-
-                rtc_intr = CMOS_READ(RTC_INTR_FLAGS);
-                rtc_intr &= (rtc_control & RTC_IRQMASK) | RTC_IRQF;
-                if (is_intr(rtc_intr))
-                        rtc_update_irq(cmos->rtc, 1, rtc_intr);
-        }
+        if (t->enabled)
+                cmos_irq_enable(cmos, RTC_AIE);
 
         spin_unlock_irq(&rtc_lock);
 
@@ -335,28 +364,17 @@ static int cmos_irq_set_freq(struct device *dev, int freq)
 static int cmos_irq_set_state(struct device *dev, int enabled)
 {
         struct cmos_rtc *cmos = dev_get_drvdata(dev);
-        unsigned char   rtc_control, rtc_intr;
         unsigned long   flags;
 
         if (!is_valid_irq(cmos->irq))
                 return -ENXIO;
 
         spin_lock_irqsave(&rtc_lock, flags);
-        rtc_control = CMOS_READ(RTC_CONTROL);
-
-        if (enabled) {
-                rtc_control |= RTC_PIE;
-                hpet_set_rtc_irq_bit(RTC_PIE);
-        } else {
-                rtc_control &= ~RTC_PIE;
-                hpet_mask_rtc_irq_bit(RTC_PIE);
-        }
-        CMOS_WRITE(rtc_control, RTC_CONTROL);
 
-        rtc_intr = CMOS_READ(RTC_INTR_FLAGS);
-        rtc_intr &= (rtc_control & RTC_IRQMASK) | RTC_IRQF;
-        if (is_intr(rtc_intr))
-                rtc_update_irq(cmos->rtc, 1, rtc_intr);
+        if (enabled)
+                cmos_irq_enable(cmos, RTC_PIE);
+        else
+                cmos_irq_disable(cmos, RTC_PIE);
 
         spin_unlock_irqrestore(&rtc_lock, flags);
         return 0;
@@ -368,7 +386,6 @@ static int
 cmos_rtc_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
 {
         struct cmos_rtc *cmos = dev_get_drvdata(dev);
-        unsigned char   rtc_control, rtc_intr;
         unsigned long   flags;
 
         switch (cmd) {
@@ -385,32 +402,20 @@ cmos_rtc_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
         }
 
         spin_lock_irqsave(&rtc_lock, flags);
-        rtc_control = CMOS_READ(RTC_CONTROL);
         switch (cmd) {
         case RTC_AIE_OFF:       /* alarm off */
-                rtc_control &= ~RTC_AIE;
-                hpet_mask_rtc_irq_bit(RTC_AIE);
+                cmos_irq_disable(cmos, RTC_AIE);
                 break;
         case RTC_AIE_ON:        /* alarm on */
-                rtc_control |= RTC_AIE;
-                hpet_set_rtc_irq_bit(RTC_AIE);
+                cmos_irq_enable(cmos, RTC_AIE);
                 break;
         case RTC_UIE_OFF:       /* update off */
-                rtc_control &= ~RTC_UIE;
-                hpet_mask_rtc_irq_bit(RTC_UIE);
+                cmos_irq_disable(cmos, RTC_UIE);
                 break;
         case RTC_UIE_ON:        /* update on */
-                rtc_control |= RTC_UIE;
-                hpet_set_rtc_irq_bit(RTC_UIE);
+                cmos_irq_enable(cmos, RTC_UIE);
                 break;
         }
-        CMOS_WRITE(rtc_control, RTC_CONTROL);
-
-        rtc_intr = CMOS_READ(RTC_INTR_FLAGS);
-        rtc_intr &= (rtc_control & RTC_IRQMASK) | RTC_IRQF;
-        if (is_intr(rtc_intr))
-                rtc_update_irq(cmos->rtc, 1, rtc_intr);
-
         spin_unlock_irqrestore(&rtc_lock, flags);
         return 0;
 }
@@ -571,7 +576,6 @@ static irqreturn_t cmos_interrupt(int irq, void *p)
          * alarm woke the system.
          */
         if (irqstat & RTC_AIE) {
-                rtc_control = CMOS_READ(RTC_CONTROL);
                 rtc_control &= ~RTC_AIE;
                 CMOS_WRITE(rtc_control, RTC_CONTROL);
                 hpet_mask_rtc_irq_bit(RTC_AIE);
@@ -685,17 +689,10 @@ cmos_do_probe(struct device *dev, struct resource *ports, int rtc_irq)
         hpet_set_periodic_freq(cmos_rtc.rtc->irq_freq);
         CMOS_WRITE(RTC_REF_CLCK_32KHZ | 0x06, RTC_FREQ_SELECT);
 
-        /* disable irqs.
-         *
-         * NOTE after changing RTC_xIE bits we always read INTR_FLAGS;
-         * allegedly some older rtcs need that to handle irqs properly
-         */
-        rtc_control = CMOS_READ(RTC_CONTROL);
-        rtc_control &= ~(RTC_PIE | RTC_AIE | RTC_UIE);
-        CMOS_WRITE(rtc_control, RTC_CONTROL);
-        hpet_mask_rtc_irq_bit(RTC_PIE | RTC_AIE | RTC_UIE);
+        /* disable irqs */
+        cmos_irq_disable(&cmos_rtc, RTC_PIE | RTC_AIE | RTC_UIE);
 
-        CMOS_READ(RTC_INTR_FLAGS);
+        rtc_control = CMOS_READ(RTC_CONTROL);
 
         spin_unlock_irq(&rtc_lock);
 
@@ -768,15 +765,8 @@ cleanup0:
 
 static void cmos_do_shutdown(void)
 {
-        unsigned char   rtc_control;
-
         spin_lock_irq(&rtc_lock);
-        rtc_control = CMOS_READ(RTC_CONTROL);
-        rtc_control &= ~RTC_IRQMASK;
-        CMOS_WRITE(rtc_control, RTC_CONTROL);
-        hpet_mask_rtc_irq_bit(RTC_IRQMASK);
-
-        CMOS_READ(RTC_INTR_FLAGS);
+        cmos_irq_disable(&cmos_rtc, RTC_IRQMASK);
         spin_unlock_irq(&rtc_lock);
 }
 
@@ -817,7 +807,6 @@ static int cmos_suspend(struct device *dev, pm_message_t mesg)
         spin_lock_irq(&rtc_lock);
         cmos->suspend_ctrl = tmp = CMOS_READ(RTC_CONTROL);
         if (tmp & (RTC_PIE|RTC_AIE|RTC_UIE)) {
-                unsigned char   irqstat;
                 unsigned char   mask;
 
                 if (do_wake)
@@ -828,10 +817,7 @@ static int cmos_suspend(struct device *dev, pm_message_t mesg)
                 CMOS_WRITE(tmp, RTC_CONTROL);
                 hpet_mask_rtc_irq_bit(mask);
 
-                irqstat = CMOS_READ(RTC_INTR_FLAGS);
-                irqstat &= (tmp & RTC_IRQMASK) | RTC_IRQF;
-                if (is_intr(irqstat))
-                        rtc_update_irq(cmos->rtc, 1, irqstat);
+                cmos_checkintr(cmos, tmp);
         }
         spin_unlock_irq(&rtc_lock);
 
@@ -875,7 +861,7 @@ static int cmos_resume(struct device *dev)
 
                         mask = CMOS_READ(RTC_INTR_FLAGS);
                         mask &= (tmp & RTC_IRQMASK) | RTC_IRQF;
-                        if (!is_intr(mask))
+                        if (!is_hpet_enabled() || !is_intr(mask))
                                 break;
 
                         /* force one-shot behavior if HPET blocked