1 files changed, 450 insertions, 0 deletions

diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h
new file mode 100644
index 000000000000..d7a2555a886c
--- /dev/null
+++ b/include/linux/jiffies.h
@@ -0,0 +1,450 @@
+#ifndef _LINUX_JIFFIES_H
+#define _LINUX_JIFFIES_H
+
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/time.h>
+#include <linux/timex.h>
+#include <asm/param.h>                  /* for HZ */
+#include <asm/div64.h>
+
+#ifndef div_long_long_rem
+#define div_long_long_rem(dividend,divisor,remainder) \
+({                                                      \
+        u64 result = dividend;                          \
+        *remainder = do_div(result,divisor);            \
+        result;                                         \
+})
+#endif
+
+/*
+ * The following defines establish the engineering parameters of the PLL
+ * model. The HZ variable establishes the timer interrupt frequency, 100 Hz
+ * for the SunOS kernel, 256 Hz for the Ultrix kernel and 1024 Hz for the
+ * OSF/1 kernel. The SHIFT_HZ define expresses the same value as the
+ * nearest power of two in order to avoid hardware multiply operations.
+ */
+#if HZ >= 12 && HZ < 24
+# define SHIFT_HZ       4
+#elif HZ >= 24 && HZ < 48
+# define SHIFT_HZ       5
+#elif HZ >= 48 && HZ < 96
+# define SHIFT_HZ       6
+#elif HZ >= 96 && HZ < 192
+# define SHIFT_HZ       7
+#elif HZ >= 192 && HZ < 384
+# define SHIFT_HZ       8
+#elif HZ >= 384 && HZ < 768
+# define SHIFT_HZ       9
+#elif HZ >= 768 && HZ < 1536
+# define SHIFT_HZ       10
+#else
+# error You lose.
+#endif
+
+/* LATCH is used in the interval timer and ftape setup. */
+#define LATCH  ((CLOCK_TICK_RATE + HZ/2) / HZ)  /* For divider */
+
+/* Suppose we want to devide two numbers NOM and DEN: NOM/DEN, the we can
+ * improve accuracy by shifting LSH bits, hence calculating:
+ *     (NOM << LSH) / DEN
+ * This however means trouble for large NOM, because (NOM << LSH) may no
+ * longer fit in 32 bits. The following way of calculating this gives us
+ * some slack, under the following conditions:
+ *   - (NOM / DEN) fits in (32 - LSH) bits.
+ *   - (NOM % DEN) fits in (32 - LSH) bits.
+ */
+#define SH_DIV(NOM,DEN,LSH) (   ((NOM / DEN) << LSH)                    \
+                             + (((NOM % DEN) << LSH) + DEN / 2) / DEN)
+
+/* HZ is the requested value. ACTHZ is actual HZ ("<< 8" is for accuracy) */
+#define ACTHZ (SH_DIV (CLOCK_TICK_RATE, LATCH, 8))
+
+/* TICK_NSEC is the time between ticks in nsec assuming real ACTHZ */
+#define TICK_NSEC (SH_DIV (1000000UL * 1000, ACTHZ, 8))
+
+/* TICK_USEC is the time between ticks in usec assuming fake USER_HZ */
+#define TICK_USEC ((1000000UL + USER_HZ/2) / USER_HZ)
+
+/* TICK_USEC_TO_NSEC is the time between ticks in nsec assuming real ACTHZ and  */
+/* a value TUSEC for TICK_USEC (can be set bij adjtimex)                */
+#define TICK_USEC_TO_NSEC(TUSEC) (SH_DIV (TUSEC * USER_HZ * 1000, ACTHZ, 8))
+
+/* some arch's have a small-data section that can be accessed register-relative
+ * but that can only take up to, say, 4-byte variables. jiffies being part of
+ * an 8-byte variable may not be correctly accessed unless we force the issue
+ */
+#define __jiffy_data  __attribute__((section(".data")))
+
+/*
+ * The 64-bit value is not volatile - you MUST NOT read it
+ * without sampling the sequence number in xtime_lock.
+ * get_jiffies_64() will do this for you as appropriate.
+ */
+extern u64 __jiffy_data jiffies_64;
+extern unsigned long volatile __jiffy_data jiffies;
+
+#if (BITS_PER_LONG < 64)
+u64 get_jiffies_64(void);
+#else
+static inline u64 get_jiffies_64(void)
+{
+        return (u64)jiffies;
+}
+#endif
+
+/*
+ *      These inlines deal with timer wrapping correctly. You are 
+ *      strongly encouraged to use them
+ *      1. Because people otherwise forget
+ *      2. Because if the timer wrap changes in future you won't have to
+ *         alter your driver code.
+ *
+ * time_after(a,b) returns true if the time a is after time b.
+ *
+ * Do this with "<0" and ">=0" to only test the sign of the result. A
+ * good compiler would generate better code (and a really good compiler
+ * wouldn't care). Gcc is currently neither.
+ */
+#define time_after(a,b)         \
+        (typecheck(unsigned long, a) && \
+         typecheck(unsigned long, b) && \
+         ((long)(b) - (long)(a) < 0))
+#define time_before(a,b)        time_after(b,a)
+
+#define time_after_eq(a,b)      \
+        (typecheck(unsigned long, a) && \
+         typecheck(unsigned long, b) && \
+         ((long)(a) - (long)(b) >= 0))
+#define time_before_eq(a,b)     time_after_eq(b,a)
+
+/*
+ * Have the 32 bit jiffies value wrap 5 minutes after boot
+ * so jiffies wrap bugs show up earlier.
+ */
+#define INITIAL_JIFFIES ((unsigned long)(unsigned int) (-300*HZ))
+
+/*
+ * Change timeval to jiffies, trying to avoid the
+ * most obvious overflows..
+ *
+ * And some not so obvious.
+ *
+ * Note that we don't want to return MAX_LONG, because
+ * for various timeout reasons we often end up having
+ * to wait "jiffies+1" in order to guarantee that we wait
+ * at _least_ "jiffies" - so "jiffies+1" had better still
+ * be positive.
+ */
+#define MAX_JIFFY_OFFSET ((~0UL >> 1)-1)
+
+/*
+ * We want to do realistic conversions of time so we need to use the same
+ * values the update wall clock code uses as the jiffies size.  This value
+ * is: TICK_NSEC (which is defined in timex.h).  This
+ * is a constant and is in nanoseconds.  We will used scaled math
+ * with a set of scales defined here as SEC_JIFFIE_SC,  USEC_JIFFIE_SC and
+ * NSEC_JIFFIE_SC.  Note that these defines contain nothing but
+ * constants and so are computed at compile time.  SHIFT_HZ (computed in
+ * timex.h) adjusts the scaling for different HZ values.
+
+ * Scaled math???  What is that?
+ *
+ * Scaled math is a way to do integer math on values that would,
+ * otherwise, either overflow, underflow, or cause undesired div
+ * instructions to appear in the execution path.  In short, we "scale"
+ * up the operands so they take more bits (more precision, less
+ * underflow), do the desired operation and then "scale" the result back
+ * by the same amount.  If we do the scaling by shifting we avoid the
+ * costly mpy and the dastardly div instructions.
+
+ * Suppose, for example, we want to convert from seconds to jiffies
+ * where jiffies is defined in nanoseconds as NSEC_PER_JIFFIE.  The
+ * simple math is: jiff = (sec * NSEC_PER_SEC) / NSEC_PER_JIFFIE; We
+ * observe that (NSEC_PER_SEC / NSEC_PER_JIFFIE) is a constant which we
+ * might calculate at compile time, however, the result will only have
+ * about 3-4 bits of precision (less for smaller values of HZ).
+ *
+ * So, we scale as follows:
+ * jiff = (sec) * (NSEC_PER_SEC / NSEC_PER_JIFFIE);
+ * jiff = ((sec) * ((NSEC_PER_SEC * SCALE)/ NSEC_PER_JIFFIE)) / SCALE;
+ * Then we make SCALE a power of two so:
+ * jiff = ((sec) * ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE)) >> SCALE;
+ * Now we define:
+ * #define SEC_CONV = ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE))
+ * jiff = (sec * SEC_CONV) >> SCALE;
+ *
+ * Often the math we use will expand beyond 32-bits so we tell C how to
+ * do this and pass the 64-bit result of the mpy through the ">> SCALE"
+ * which should take the result back to 32-bits.  We want this expansion
+ * to capture as much precision as possible.  At the same time we don't
+ * want to overflow so we pick the SCALE to avoid this.  In this file,
+ * that means using a different scale for each range of HZ values (as
+ * defined in timex.h).
+ *
+ * For those who want to know, gcc will give a 64-bit result from a "*"
+ * operator if the result is a long long AND at least one of the
+ * operands is cast to long long (usually just prior to the "*" so as
+ * not to confuse it into thinking it really has a 64-bit operand,
+ * which, buy the way, it can do, but it take more code and at least 2
+ * mpys).
+
+ * We also need to be aware that one second in nanoseconds is only a
+ * couple of bits away from overflowing a 32-bit word, so we MUST use
+ * 64-bits to get the full range time in nanoseconds.
+
+ */
+
+/*
+ * Here are the scales we will use.  One for seconds, nanoseconds and
+ * microseconds.
+ *
+ * Within the limits of cpp we do a rough cut at the SEC_JIFFIE_SC and
+ * check if the sign bit is set.  If not, we bump the shift count by 1.
+ * (Gets an extra bit of precision where we can use it.)
+ * We know it is set for HZ = 1024 and HZ = 100 not for 1000.
+ * Haven't tested others.
+
+ * Limits of cpp (for #if expressions) only long (no long long), but
+ * then we only need the most signicant bit.
+ */
+
+#define SEC_JIFFIE_SC (31 - SHIFT_HZ)
+#if !((((NSEC_PER_SEC << 2) / TICK_NSEC) << (SEC_JIFFIE_SC - 2)) & 0x80000000)
+#undef SEC_JIFFIE_SC
+#define SEC_JIFFIE_SC (32 - SHIFT_HZ)
+#endif
+#define NSEC_JIFFIE_SC (SEC_JIFFIE_SC + 29)
+#define USEC_JIFFIE_SC (SEC_JIFFIE_SC + 19)
+#define SEC_CONVERSION ((unsigned long)((((u64)NSEC_PER_SEC << SEC_JIFFIE_SC) +\
+                                TICK_NSEC -1) / (u64)TICK_NSEC))
+
+#define NSEC_CONVERSION ((unsigned long)((((u64)1 << NSEC_JIFFIE_SC) +\
+                                        TICK_NSEC -1) / (u64)TICK_NSEC))
+#define USEC_CONVERSION  \
+                    ((unsigned long)((((u64)NSEC_PER_USEC << USEC_JIFFIE_SC) +\
+                                        TICK_NSEC -1) / (u64)TICK_NSEC))
+/*
+ * USEC_ROUND is used in the timeval to jiffie conversion.  See there
+ * for more details.  It is the scaled resolution rounding value.  Note
+ * that it is a 64-bit value.  Since, when it is applied, we are already
+ * in jiffies (albit scaled), it is nothing but the bits we will shift
+ * off.
+ */
+#define USEC_ROUND (u64)(((u64)1 << USEC_JIFFIE_SC) - 1)
+/*
+ * The maximum jiffie value is (MAX_INT >> 1).  Here we translate that
+ * into seconds.  The 64-bit case will overflow if we are not careful,
+ * so use the messy SH_DIV macro to do it.  Still all constants.
+ */
+#if BITS_PER_LONG < 64
+# define MAX_SEC_IN_JIFFIES \
+        (long)((u64)((u64)MAX_JIFFY_OFFSET * TICK_NSEC) / NSEC_PER_SEC)
+#else   /* take care of overflow on 64 bits machines */
+# define MAX_SEC_IN_JIFFIES \
+        (SH_DIV((MAX_JIFFY_OFFSET >> SEC_JIFFIE_SC) * TICK_NSEC, NSEC_PER_SEC, 1) - 1)
+
+#endif
+
+/*
+ * Convert jiffies to milliseconds and back.
+ *
+ * Avoid unnecessary multiplications/divisions in the
+ * two most common HZ cases:
+ */
+static inline unsigned int jiffies_to_msecs(const unsigned long j)
+{
+#if HZ <= 1000 && !(1000 % HZ)
+        return (1000 / HZ) * j;
+#elif HZ > 1000 && !(HZ % 1000)
+        return (j + (HZ / 1000) - 1)/(HZ / 1000);
+#else
+        return (j * 1000) / HZ;
+#endif
+}
+
+static inline unsigned int jiffies_to_usecs(const unsigned long j)
+{
+#if HZ <= 1000000 && !(1000000 % HZ)
+        return (1000000 / HZ) * j;
+#elif HZ > 1000000 && !(HZ % 1000000)
+        return (j + (HZ / 1000000) - 1)/(HZ / 1000000);
+#else
+        return (j * 1000000) / HZ;
+#endif
+}
+
+static inline unsigned long msecs_to_jiffies(const unsigned int m)
+{
+        if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
+                return MAX_JIFFY_OFFSET;
+#if HZ <= 1000 && !(1000 % HZ)
+        return (m + (1000 / HZ) - 1) / (1000 / HZ);
+#elif HZ > 1000 && !(HZ % 1000)
+        return m * (HZ / 1000);
+#else
+        return (m * HZ + 999) / 1000;
+#endif
+}
+
+static inline unsigned long usecs_to_jiffies(const unsigned int u)
+{
+        if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
+                return MAX_JIFFY_OFFSET;
+#if HZ <= 1000000 && !(1000000 % HZ)
+        return (u + (1000000 / HZ) - 1) / (1000000 / HZ);
+#elif HZ > 1000000 && !(HZ % 1000000)
+        return u * (HZ / 1000000);
+#else
+        return (u * HZ + 999999) / 1000000;
+#endif
+}
+
+/*
+ * 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.
+ */
+static __inline__ 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;
+
+}
+
+static __inline__ 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);
+}
+
+/* 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.
+ */
+static __inline__ 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;
+}
+
+static __inline__ 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;
+        value->tv_sec = div_long_long_rem(nsec, NSEC_PER_SEC, &value->tv_usec);
+        value->tv_usec /= NSEC_PER_USEC;
+}
+
+/*
+ * Convert jiffies/jiffies_64 to clock_t and back.
+ */
+static inline 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
+}
+
+static inline 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
+}
+
+static inline 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;
+}
+
+static inline 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;
+}
+
+#endif