1 files changed, 213 insertions, 0 deletions

diff --git a/kernel/time.c b/kernel/time.c
index 0e017bff4c19..4a8657171584 100644
--- a/kernel/time.c
+++ b/kernel/time.c
@@ -470,6 +470,219 @@ struct timeval ns_to_timeval(const s64 nsec)
         return tv;
 }
 
+/*
+ * Convert jiffies to milliseconds and back.
+ *
+ * Avoid unnecessary multiplications/divisions in the
+ * two most common HZ cases:
+ */
+unsigned int jiffies_to_msecs(const unsigned long j)
+{
+#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
+        return (MSEC_PER_SEC / HZ) * j;
+#elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
+        return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC);
+#else
+        return (j * MSEC_PER_SEC) / HZ;
+#endif
+}
+EXPORT_SYMBOL(jiffies_to_msecs);
+
+unsigned int jiffies_to_usecs(const unsigned long j)
+{
+#if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
+        return (USEC_PER_SEC / HZ) * j;
+#elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
+        return (j + (HZ / USEC_PER_SEC) - 1)/(HZ / USEC_PER_SEC);
+#else
+        return (j * USEC_PER_SEC) / HZ;
+#endif
+}
+EXPORT_SYMBOL(jiffies_to_usecs);
+
+unsigned long msecs_to_jiffies(const unsigned int m)
+{
+        if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
+                return MAX_JIFFY_OFFSET;
+#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
+        return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ);
+#elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
+        return m * (HZ / MSEC_PER_SEC);
+#else
+        return (m * HZ + MSEC_PER_SEC - 1) / MSEC_PER_SEC;
+#endif
+}
+EXPORT_SYMBOL(msecs_to_jiffies);
+
+unsigned long usecs_to_jiffies(const unsigned int u)
+{
+        if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
+                return MAX_JIFFY_OFFSET;
+#if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
+        return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ);
+#elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
+        return u * (HZ / USEC_PER_SEC);
+#else
+        return (u * HZ + USEC_PER_SEC - 1) / USEC_PER_SEC;
+#endif
+}
+EXPORT_SYMBOL(usecs_to_jiffies);
+
+/*
+ * The TICK_NSEC - 1 rounds up the value to the next resolution.  Note
+ * that a remainder subtract here would not do the right thing as the
+ * resolution values don't fall on second boundries.  I.e. the line:
+ * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding.
+ *
+ * Rather, we just shift the bits off the right.
+ *
+ * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec
+ * value to a scaled second value.
+ */
+unsigned long
+timespec_to_jiffies(const struct timespec *value)
+{
+        unsigned long sec = value->tv_sec;
+        long nsec = value->tv_nsec + TICK_NSEC - 1;
+
+        if (sec >= MAX_SEC_IN_JIFFIES){
+                sec = MAX_SEC_IN_JIFFIES;
+                nsec = 0;
+        }
+        return (((u64)sec * SEC_CONVERSION) +
+                (((u64)nsec * NSEC_CONVERSION) >>
+                 (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
+
+}
+EXPORT_SYMBOL(timespec_to_jiffies);
+
+void
+jiffies_to_timespec(const unsigned long jiffies, struct timespec *value)
+{
+        /*
+         * Convert jiffies to nanoseconds and separate with
+         * one divide.
+         */
+        u64 nsec = (u64)jiffies * TICK_NSEC;
+        value->tv_sec = div_long_long_rem(nsec, NSEC_PER_SEC, &value->tv_nsec);
+}
+EXPORT_SYMBOL(jiffies_to_timespec);
+
+/* Same for "timeval"
+ *
+ * Well, almost.  The problem here is that the real system resolution is
+ * in nanoseconds and the value being converted is in micro seconds.
+ * Also for some machines (those that use HZ = 1024, in-particular),
+ * there is a LARGE error in the tick size in microseconds.
+
+ * The solution we use is to do the rounding AFTER we convert the
+ * microsecond part.  Thus the USEC_ROUND, the bits to be shifted off.
+ * Instruction wise, this should cost only an additional add with carry
+ * instruction above the way it was done above.
+ */
+unsigned long
+timeval_to_jiffies(const struct timeval *value)
+{
+        unsigned long sec = value->tv_sec;
+        long usec = value->tv_usec;
+
+        if (sec >= MAX_SEC_IN_JIFFIES){
+                sec = MAX_SEC_IN_JIFFIES;
+                usec = 0;
+        }
+        return (((u64)sec * SEC_CONVERSION) +
+                (((u64)usec * USEC_CONVERSION + USEC_ROUND) >>
+                 (USEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
+}
+
+void jiffies_to_timeval(const unsigned long jiffies, struct timeval *value)
+{
+        /*
+         * Convert jiffies to nanoseconds and separate with
+         * one divide.
+         */
+        u64 nsec = (u64)jiffies * TICK_NSEC;
+        long tv_usec;
+
+        value->tv_sec = div_long_long_rem(nsec, NSEC_PER_SEC, &tv_usec);
+        tv_usec /= NSEC_PER_USEC;
+        value->tv_usec = tv_usec;
+}
+
+/*
+ * Convert jiffies/jiffies_64 to clock_t and back.
+ */
+clock_t jiffies_to_clock_t(long x)
+{
+#if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
+        return x / (HZ / USER_HZ);
+#else
+        u64 tmp = (u64)x * TICK_NSEC;
+        do_div(tmp, (NSEC_PER_SEC / USER_HZ));
+        return (long)tmp;
+#endif
+}
+EXPORT_SYMBOL(jiffies_to_clock_t);
+
+unsigned long clock_t_to_jiffies(unsigned long x)
+{
+#if (HZ % USER_HZ)==0
+        if (x >= ~0UL / (HZ / USER_HZ))
+                return ~0UL;
+        return x * (HZ / USER_HZ);
+#else
+        u64 jif;
+
+        /* Don't worry about loss of precision here .. */
+        if (x >= ~0UL / HZ * USER_HZ)
+                return ~0UL;
+
+        /* .. but do try to contain it here */
+        jif = x * (u64) HZ;
+        do_div(jif, USER_HZ);
+        return jif;
+#endif
+}
+EXPORT_SYMBOL(clock_t_to_jiffies);
+
+u64 jiffies_64_to_clock_t(u64 x)
+{
+#if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
+        do_div(x, HZ / USER_HZ);
+#else
+        /*
+         * There are better ways that don't overflow early,
+         * but even this doesn't overflow in hundreds of years
+         * in 64 bits, so..
+         */
+        x *= TICK_NSEC;
+        do_div(x, (NSEC_PER_SEC / USER_HZ));
+#endif
+        return x;
+}
+
+EXPORT_SYMBOL(jiffies_64_to_clock_t);
+
+u64 nsec_to_clock_t(u64 x)
+{
+#if (NSEC_PER_SEC % USER_HZ) == 0
+        do_div(x, (NSEC_PER_SEC / USER_HZ));
+#elif (USER_HZ % 512) == 0
+        x *= USER_HZ/512;
+        do_div(x, (NSEC_PER_SEC / 512));
+#else
+        /*
+         * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
+         * overflow after 64.99 years.
+         * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
+         */
+        x *= 9;
+        do_div(x, (unsigned long)((9ull * NSEC_PER_SEC + (USER_HZ/2)) /
+                                  USER_HZ));
+#endif
+        return x;
+}
+
 #if (BITS_PER_LONG < 64)
 u64 get_jiffies_64(void)
 {