include/linux/ktime.h

   1 /*
   2  *  include/linux/ktime.h
   3  *
   4  *  ktime_t - nanosecond-resolution time format.
   5  *
   6  *   Copyright(C) 2005, Thomas Gleixner <tglx@linutronix.de>
   7  *   Copyright(C) 2005, Red Hat, Inc., Ingo Molnar
   8  *
   9  *  data type definitions, declarations, prototypes and macros.
  10  *
  11  *  Started by: Thomas Gleixner and Ingo Molnar
  12  *
  13  *  Credits:
  14  *
  15  *      Roman Zippel provided the ideas and primary code snippets of
  16  *      the ktime_t union and further simplifications of the original
  17  *      code.
  18  *
  19  *  For licencing details see kernel-base/COPYING
  20  */
  21 #ifndef _LINUX_KTIME_H
  22 #define _LINUX_KTIME_H
  23
  24 #include <linux/time.h>
  25 #include <linux/jiffies.h>
  26
  27 /*
  28  * ktime_t:
  29  *
  30  * On 64-bit CPUs a single 64-bit variable is used to store the hrtimers
  31  * internal representation of time values in scalar nanoseconds. The
  32  * design plays out best on 64-bit CPUs, where most conversions are
  33  * NOPs and most arithmetic ktime_t operations are plain arithmetic
  34  * operations.
  35  *
  36  * On 32-bit CPUs an optimized representation of the timespec structure
  37  * is used to avoid expensive conversions from and to timespecs. The
  38  * endian-aware order of the tv struct members is choosen to allow
  39  * mathematical operations on the tv64 member of the union too, which
  40  * for certain operations produces better code.
  41  *
  42  * For architectures with efficient support for 64/32-bit conversions the
  43  * plain scalar nanosecond based representation can be selected by the
  44  * config switch CONFIG_KTIME_SCALAR.
  45  */
  46 typedef union {
  47         s64     tv64;
  48 #if BITS_PER_LONG != 64 && !defined(CONFIG_KTIME_SCALAR)
  49         struct {
  50 # ifdef __BIG_ENDIAN
  51         s32     sec, nsec;
  52 # else
  53         s32     nsec, sec;
  54 # endif
  55         } tv;
  56 #endif
  57 } ktime_t;
  58
  59 #define KTIME_MAX                       ((s64)~((u64)1 << 63))
  60 #define KTIME_SEC_MAX                   (KTIME_MAX / NSEC_PER_SEC)
  61
  62 /*
  63  * ktime_t definitions when using the 64-bit scalar representation:
  64  */
  65
  66 #if (BITS_PER_LONG == 64) || defined(CONFIG_KTIME_SCALAR)
  67
  68 /**
  69  * ktime_set - Set a ktime_t variable from a seconds/nanoseconds value
  70  * @secs:       seconds to set
  71  * @nsecs:      nanoseconds to set
  72  *
  73  * Return the ktime_t representation of the value
  74  */
  75 static inline ktime_t ktime_set(const long secs, const unsigned long nsecs)
  76 {
  77 #if (BITS_PER_LONG == 64)
  78         if (unlikely(secs >= KTIME_SEC_MAX))
  79                 return (ktime_t){ .tv64 = KTIME_MAX };
  80 #endif
  81         return (ktime_t) { .tv64 = (s64)secs * NSEC_PER_SEC + (s64)nsecs };
  82 }
  83
  84 /* Subtract two ktime_t variables. rem = lhs -rhs: */
  85 #define ktime_sub(lhs, rhs) \
  86                 ({ (ktime_t){ .tv64 = (lhs).tv64 - (rhs).tv64 }; })
  87
  88 /* Add two ktime_t variables. res = lhs + rhs: */
  89 #define ktime_add(lhs, rhs) \
  90                 ({ (ktime_t){ .tv64 = (lhs).tv64 + (rhs).tv64 }; })
  91
  92 /*
  93  * Add a ktime_t variable and a scalar nanosecond value.
  94  * res = kt + nsval:
  95  */
  96 #define ktime_add_ns(kt, nsval) \
  97                 ({ (ktime_t){ .tv64 = (kt).tv64 + (nsval) }; })
  98
  99 /* convert a timespec to ktime_t format: */
 100 static inline ktime_t timespec_to_ktime(struct timespec ts)
 101 {
 102         return ktime_set(ts.tv_sec, ts.tv_nsec);
 103 }
 104
 105 /* convert a timeval to ktime_t format: */
 106 static inline ktime_t timeval_to_ktime(struct timeval tv)
 107 {
 108         return ktime_set(tv.tv_sec, tv.tv_usec * NSEC_PER_USEC);
 109 }
 110
 111 /* Map the ktime_t to timespec conversion to ns_to_timespec function */
 112 #define ktime_to_timespec(kt)           ns_to_timespec((kt).tv64)
 113
 114 /* Map the ktime_t to timeval conversion to ns_to_timeval function */
 115 #define ktime_to_timeval(kt)            ns_to_timeval((kt).tv64)
 116
 117 /* Convert ktime_t to nanoseconds - NOP in the scalar storage format: */
 118 #define ktime_to_ns(kt)                 ((kt).tv64)
 119
 120 #else
 121
 122 /*
 123  * Helper macros/inlines to get the ktime_t math right in the timespec
 124  * representation. The macros are sometimes ugly - their actual use is
 125  * pretty okay-ish, given the circumstances. We do all this for
 126  * performance reasons. The pure scalar nsec_t based code was nice and
 127  * simple, but created too many 64-bit / 32-bit conversions and divisions.
 128  *
 129  * Be especially aware that negative values are represented in a way
 130  * that the tv.sec field is negative and the tv.nsec field is greater
 131  * or equal to zero but less than nanoseconds per second. This is the
 132  * same representation which is used by timespecs.
 133  *
 134  *   tv.sec < 0 and 0 >= tv.nsec < NSEC_PER_SEC
 135  */
 136
 137 /* Set a ktime_t variable to a value in sec/nsec representation: */
 138 static inline ktime_t ktime_set(const long secs, const unsigned long nsecs)
 139 {
 140         return (ktime_t) { .tv = { .sec = secs, .nsec = nsecs } };
 141 }
 142
 143 /**
 144  * ktime_sub - subtract two ktime_t variables
 145  * @lhs:        minuend
 146  * @rhs:        subtrahend
 147  *
 148  * Returns the remainder of the substraction
 149  */
 150 static inline ktime_t ktime_sub(const ktime_t lhs, const ktime_t rhs)
 151 {
 152         ktime_t res;
 153
 154         res.tv64 = lhs.tv64 - rhs.tv64;
 155         if (res.tv.nsec < 0)
 156                 res.tv.nsec += NSEC_PER_SEC;
 157
 158         return res;
 159 }
 160
 161 /**
 162  * ktime_add - add two ktime_t variables
 163  * @add1:       addend1
 164  * @add2:       addend2
 165  *
 166  * Returns the sum of @add1 and @add2.
 167  */
 168 static inline ktime_t ktime_add(const ktime_t add1, const ktime_t add2)
 169 {
 170         ktime_t res;
 171
 172         res.tv64 = add1.tv64 + add2.tv64;
 173         /*
 174          * performance trick: the (u32) -NSEC gives 0x00000000Fxxxxxxx
 175          * so we subtract NSEC_PER_SEC and add 1 to the upper 32 bit.
 176          *
 177          * it's equivalent to:
 178          *   tv.nsec -= NSEC_PER_SEC
 179          *   tv.sec ++;
 180          */
 181         if (res.tv.nsec >= NSEC_PER_SEC)
 182                 res.tv64 += (u32)-NSEC_PER_SEC;
 183
 184         return res;
 185 }
 186
 187 /**
 188  * ktime_add_ns - Add a scalar nanoseconds value to a ktime_t variable
 189  * @kt:         addend
 190  * @nsec:       the scalar nsec value to add
 191  *
 192  * Returns the sum of @kt and @nsec in ktime_t format
 193  */
 194 extern ktime_t ktime_add_ns(const ktime_t kt, u64 nsec);
 195
 196 /**
 197  * timespec_to_ktime - convert a timespec to ktime_t format
 198  * @ts:         the timespec variable to convert
 199  *
 200  * Returns a ktime_t variable with the converted timespec value
 201  */
 202 static inline ktime_t timespec_to_ktime(const struct timespec ts)
 203 {
 204         return (ktime_t) { .tv = { .sec = (s32)ts.tv_sec,
 205                                    .nsec = (s32)ts.tv_nsec } };
 206 }
 207
 208 /**
 209  * timeval_to_ktime - convert a timeval to ktime_t format
 210  * @tv:         the timeval variable to convert
 211  *
 212  * Returns a ktime_t variable with the converted timeval value
 213  */
 214 static inline ktime_t timeval_to_ktime(const struct timeval tv)
 215 {
 216         return (ktime_t) { .tv = { .sec = (s32)tv.tv_sec,
 217                                    .nsec = (s32)tv.tv_usec * 1000 } };
 218 }
 219
 220 /**
 221  * ktime_to_timespec - convert a ktime_t variable to timespec format
 222  * @kt:         the ktime_t variable to convert
 223  *
 224  * Returns the timespec representation of the ktime value
 225  */
 226 static inline struct timespec ktime_to_timespec(const ktime_t kt)
 227 {
 228         return (struct timespec) { .tv_sec = (time_t) kt.tv.sec,
 229                                    .tv_nsec = (long) kt.tv.nsec };
 230 }
 231
 232 /**
 233  * ktime_to_timeval - convert a ktime_t variable to timeval format
 234  * @kt:         the ktime_t variable to convert
 235  *
 236  * Returns the timeval representation of the ktime value
 237  */
 238 static inline struct timeval ktime_to_timeval(const ktime_t kt)
 239 {
 240         return (struct timeval) {
 241                 .tv_sec = (time_t) kt.tv.sec,
 242                 .tv_usec = (suseconds_t) (kt.tv.nsec / NSEC_PER_USEC) };
 243 }
 244
 245 /**
 246  * ktime_to_ns - convert a ktime_t variable to scalar nanoseconds
 247  * @kt:         the ktime_t variable to convert
 248  *
 249  * Returns the scalar nanoseconds representation of @kt
 250  */
 251 static inline s64 ktime_to_ns(const ktime_t kt)
 252 {
 253         return (s64) kt.tv.sec * NSEC_PER_SEC + kt.tv.nsec;
 254 }
 255
 256 #endif
 257
 258 /*
 259  * The resolution of the clocks. The resolution value is returned in
 260  * the clock_getres() system call to give application programmers an
 261  * idea of the (in)accuracy of timers. Timer values are rounded up to
 262  * this resolution values.
 263  */
 264 #define KTIME_LOW_RES           (ktime_t){ .tv64 = TICK_NSEC }
 265
 266 /* Get the monotonic time in timespec format: */
 267 extern void ktime_get_ts(struct timespec *ts);
 268
 269 /* Get the real (wall-) time in timespec format: */
 270 #define ktime_get_real_ts(ts)   getnstimeofday(ts)
 271
 272 #endif