drivers/rtc/rtc-at91rm9200.c: use a variable for storing IMR

On some revisions of AT91 SoCs, the RTC IMR register is not working.
Instead of elaborating a workaround for that specific SoC or IP version,
we simply use a software variable to store the Interrupt Mask Register
and modify it for each enabling/disabling of an interrupt.  The overhead
of this is negligible anyway.

The interrupt mask register (IMR) for the RTC is broken on the AT91SAM9x5
sub-family of SoCs (good overview of the members here:
http://www.eewiki.net/display/linuxonarm/AT91SAM9x5 ).  The "user visible
effect" is the RTC doesn't work.

That sub-family is less than two years old and only has devicetree (DT)
support and came online circa lk 3.7 .  The dust is yet to settle on the
DT stuff at least for AT91 SoCs (translation: lots of stuff is still
broken, so much that it is hard to know where to start).

The fix in the patch is pretty simple: just shadow the silicon IMR
register with a variable in the driver.  Some older SoCs (pre-DT) use the
the rtc-at91rm9200 driver (e.g.  obviously the AT91RM9200) and they should
not be impacted by the change.  There shouldn't be a large volume of
interrupts associated with a RTC.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Reported-by: Douglas Gilbert <dgilbert@interlog.com>
Cc: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Cc: Ludovic Desroches <ludovic.desroches@atmel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 31 insertions, 19 deletions

diff --git a/drivers/rtc/rtc-at91rm9200.c b/drivers/rtc/rtc-at91rm9200.c
index 434ebc3a99dc..0a9f27e094ea 100644
--- a/drivers/rtc/rtc-at91rm9200.c
+++ b/drivers/rtc/rtc-at91rm9200.c
@@ -44,6 +44,7 @@ static DECLARE_COMPLETION(at91_rtc_updated);
 static unsigned int at91_alarm_year = AT91_RTC_EPOCH;
 static void __iomem *at91_rtc_regs;
 static int irq;
+static u32 at91_rtc_imr;
 
 /*
  * Decode time/date into rtc_time structure
@@ -108,9 +109,11 @@ static int at91_rtc_settime(struct device *dev, struct rtc_time *tm)
         cr = at91_rtc_read(AT91_RTC_CR);
         at91_rtc_write(AT91_RTC_CR, cr | AT91_RTC_UPDCAL | AT91_RTC_UPDTIM);
 
+        at91_rtc_imr |= AT91_RTC_ACKUPD;
         at91_rtc_write(AT91_RTC_IER, AT91_RTC_ACKUPD);
         wait_for_completion(&at91_rtc_updated); /* wait for ACKUPD interrupt */
         at91_rtc_write(AT91_RTC_IDR, AT91_RTC_ACKUPD);
+        at91_rtc_imr &= ~AT91_RTC_ACKUPD;
 
         at91_rtc_write(AT91_RTC_TIMR,
                           bin2bcd(tm->tm_sec) << 0
@@ -142,7 +145,7 @@ static int at91_rtc_readalarm(struct device *dev, struct rtc_wkalrm *alrm)
         tm->tm_yday = rtc_year_days(tm->tm_mday, tm->tm_mon, tm->tm_year);
         tm->tm_year = at91_alarm_year - 1900;
 
-        alrm->enabled = (at91_rtc_read(AT91_RTC_IMR) & AT91_RTC_ALARM)
+        alrm->enabled = (at91_rtc_imr & AT91_RTC_ALARM)
                         ? 1 : 0;
 
         dev_dbg(dev, "%s(): %4d-%02d-%02d %02d:%02d:%02d\n", __func__,
@@ -168,6 +171,7 @@ static int at91_rtc_setalarm(struct device *dev, struct rtc_wkalrm *alrm)
         tm.tm_sec = alrm->time.tm_sec;
 
         at91_rtc_write(AT91_RTC_IDR, AT91_RTC_ALARM);
+        at91_rtc_imr &= ~AT91_RTC_ALARM;
         at91_rtc_write(AT91_RTC_TIMALR,
                   bin2bcd(tm.tm_sec) << 0
                 | bin2bcd(tm.tm_min) << 8
@@ -180,6 +184,7 @@ static int at91_rtc_setalarm(struct device *dev, struct rtc_wkalrm *alrm)
 
         if (alrm->enabled) {
                 at91_rtc_write(AT91_RTC_SCCR, AT91_RTC_ALARM);
+                at91_rtc_imr |= AT91_RTC_ALARM;
                 at91_rtc_write(AT91_RTC_IER, AT91_RTC_ALARM);
         }
 
@@ -196,9 +201,12 @@ static int at91_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
 
         if (enabled) {
                 at91_rtc_write(AT91_RTC_SCCR, AT91_RTC_ALARM);
+                at91_rtc_imr |= AT91_RTC_ALARM;
                 at91_rtc_write(AT91_RTC_IER, AT91_RTC_ALARM);
-        } else
+        } else {
                 at91_rtc_write(AT91_RTC_IDR, AT91_RTC_ALARM);
+                at91_rtc_imr &= ~AT91_RTC_ALARM;
+        }
 
         return 0;
 }
@@ -207,12 +215,10 @@ static int at91_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
  */
 static int at91_rtc_proc(struct device *dev, struct seq_file *seq)
 {
-        unsigned long imr = at91_rtc_read(AT91_RTC_IMR);
-
         seq_printf(seq, "update_IRQ\t: %s\n",
-                        (imr & AT91_RTC_ACKUPD) ? "yes" : "no");
+                        (at91_rtc_imr & AT91_RTC_ACKUPD) ? "yes" : "no");
         seq_printf(seq, "periodic_IRQ\t: %s\n",
-                        (imr & AT91_RTC_SECEV) ? "yes" : "no");
+                        (at91_rtc_imr & AT91_RTC_SECEV) ? "yes" : "no");
 
         return 0;
 }
@@ -227,7 +233,7 @@ static irqreturn_t at91_rtc_interrupt(int irq, void *dev_id)
         unsigned int rtsr;
         unsigned long events = 0;
 
-        rtsr = at91_rtc_read(AT91_RTC_SR) & at91_rtc_read(AT91_RTC_IMR);
+        rtsr = at91_rtc_read(AT91_RTC_SR) & at91_rtc_imr;
         if (rtsr) {             /* this interrupt is shared!  Is it ours? */
                 if (rtsr & AT91_RTC_ALARM)
                         events |= (RTC_AF | RTC_IRQF);
@@ -291,6 +297,7 @@ static int __init at91_rtc_probe(struct platform_device *pdev)
         at91_rtc_write(AT91_RTC_IDR, AT91_RTC_ACKUPD | AT91_RTC_ALARM |
                                         AT91_RTC_SECEV | AT91_RTC_TIMEV |
                                         AT91_RTC_CALEV);
+        at91_rtc_imr = 0;
 
         ret = request_irq(irq, at91_rtc_interrupt,
                                 IRQF_SHARED,
@@ -329,6 +336,7 @@ static int __exit at91_rtc_remove(struct platform_device *pdev)
         at91_rtc_write(AT91_RTC_IDR, AT91_RTC_ACKUPD | AT91_RTC_ALARM |
                                         AT91_RTC_SECEV | AT91_RTC_TIMEV |
                                         AT91_RTC_CALEV);
+        at91_rtc_imr = 0;
         free_irq(irq, pdev);
 
         rtc_device_unregister(rtc);
@@ -341,31 +349,35 @@ static int __exit at91_rtc_remove(struct platform_device *pdev)
 
 /* AT91RM9200 RTC Power management control */
 
-static u32 at91_rtc_imr;
+static u32 at91_rtc_bkpimr;
+
 
 static int at91_rtc_suspend(struct device *dev)
 {
         /* this IRQ is shared with DBGU and other hardware which isn't
          * necessarily doing PM like we are...
          */
-        at91_rtc_imr = at91_rtc_read(AT91_RTC_IMR)
-                        & (AT91_RTC_ALARM|AT91_RTC_SECEV);
-        if (at91_rtc_imr) {
-                if (device_may_wakeup(dev))
+        at91_rtc_bkpimr = at91_rtc_imr & (AT91_RTC_ALARM|AT91_RTC_SECEV);
+        if (at91_rtc_bkpimr) {
+                if (device_may_wakeup(dev)) {
                         enable_irq_wake(irq);
-                else
-                        at91_rtc_write(AT91_RTC_IDR, at91_rtc_imr);
-        }
+                } else {
+                        at91_rtc_write(AT91_RTC_IDR, at91_rtc_bkpimr);
+                        at91_rtc_imr &= ~at91_rtc_bkpimr;
+                }
+}
         return 0;
 }
 
 static int at91_rtc_resume(struct device *dev)
 {
-        if (at91_rtc_imr) {
-                if (device_may_wakeup(dev))
+        if (at91_rtc_bkpimr) {
+                if (device_may_wakeup(dev)) {
                         disable_irq_wake(irq);
-                else
-                        at91_rtc_write(AT91_RTC_IER, at91_rtc_imr);
+                } else {
+                        at91_rtc_imr |= at91_rtc_bkpimr;
+                        at91_rtc_write(AT91_RTC_IER, at91_rtc_bkpimr);
+                }
         }
         return 0;
 }