Use rtc_lock to protect RTC operations

    
Many RTC routines were not protected against each other, so there are
potential races, for example, ntp-update against /dev/rtc.  This patch
fixes them using rtc_lock.
    
Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 22 insertions, 2 deletions

diff --git a/arch/mips/dec/time.c b/arch/mips/dec/time.c
index dc7091caa7aa..174822344131 100644
--- a/arch/mips/dec/time.c
+++ b/arch/mips/dec/time.c
@@ -37,10 +37,25 @@
 #include <asm/dec/machtype.h>
 
 
+/*
+ * Returns true if a clock update is in progress
+ */
+static inline unsigned char dec_rtc_is_updating(void)
+{
+        unsigned char uip;
+        unsigned long flags;
+
+        spin_lock_irqsave(&rtc_lock, flags);
+        uip = (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP);
+        spin_unlock_irqrestore(&rtc_lock, flags);
+        return uip;
+}
+
 static unsigned long dec_rtc_get_time(void)
 {
         unsigned int year, mon, day, hour, min, sec, real_year;
         int i;
+        unsigned long flags;
 
         /* The Linux interpretation of the DS1287 clock register contents:
          * When the Update-In-Progress (UIP) flag goes from 1 to 0, the
@@ -49,11 +64,12 @@ static unsigned long dec_rtc_get_time(void)
          */
         /* read RTC exactly on falling edge of update flag */
         for (i = 0; i < 1000000; i++)   /* may take up to 1 second... */
-                if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP)
+                if (dec_rtc_is_updating())
                         break;
         for (i = 0; i < 1000000; i++)   /* must try at least 2.228 ms */
-                if (!(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
+                if (!dec_rtc_is_updating())
                         break;
+        spin_lock_irqsave(&rtc_lock, flags);
         /* Isn't this overkill?  UIP above should guarantee consistency */
         do {
                 sec = CMOS_READ(RTC_SECONDS);
@@ -77,6 +93,7 @@ static unsigned long dec_rtc_get_time(void)
          * of unused BBU RAM locations.
          */
         real_year = CMOS_READ(RTC_DEC_YEAR);
+        spin_unlock_irqrestore(&rtc_lock, flags);
         year += real_year - 72 + 2000;
 
         return mktime(year, mon, day, hour, min, sec);
@@ -95,6 +112,8 @@ static int dec_rtc_set_mmss(unsigned long nowtime)
         int real_seconds, real_minutes, cmos_minutes;
         unsigned char save_control, save_freq_select;
 
+        /* irq are locally disabled here */
+        spin_lock(&rtc_lock);
         /* tell the clock it's being set */
         save_control = CMOS_READ(RTC_CONTROL);
         CMOS_WRITE((save_control | RTC_SET), RTC_CONTROL);
@@ -141,6 +160,7 @@ static int dec_rtc_set_mmss(unsigned long nowtime)
          */
         CMOS_WRITE(save_control, RTC_CONTROL);
         CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
+        spin_unlock(&rtc_lock);
 
         return retval;
 }