jiffies.h

Axis 221 camera embedded programing interface

#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 <= 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
}

static inline 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
}

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 <= 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
}

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 <= 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
}

/*
 * 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;
	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.
 */
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