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 #if (BITS_PER_LONG == 64)
  61 # define KTIME_SEC_MAX                  (KTIME_MAX / NSEC_PER_SEC)
  62 #else
  63 # define KTIME_SEC_MAX                  LONG_MAX
  64 #endif
  65
  66 /*
  67  * ktime_t definitions when using the 64-bit scalar representation:
  68  */
  69
  70 #if (BITS_PER_LONG == 64) || defined(CONFIG_KTIME_SCALAR)
  71
  72 /**
  73  * ktime_set - Set a ktime_t variable from a seconds/nanoseconds value
  74  * @secs:       seconds to set
  75  * @nsecs:      nanoseconds to set
  76  *
  77  * Return the ktime_t representation of the value
  78  */
  79 static inline ktime_t ktime_set(const long secs, const unsigned long nsecs)
  80 {
  81 #if (BITS_PER_LONG == 64)
  82         if (unlikely(secs >= KTIME_SEC_MAX))
  83                 return (ktime_t){ .tv64 = KTIME_MAX };
  84 #endif
  85         return (ktime_t) { .tv64 = (s64)secs * NSEC_PER_SEC + (s64)nsecs };
  86 }
  87
  88 /* Subtract two ktime_t variables. rem = lhs -rhs: */
  89 #define ktime_sub(lhs, rhs) \
  90                 ({ (ktime_t){ .tv64 = (lhs).tv64 - (rhs).tv64 }; })
  91
  92 /* Add two ktime_t variables. res = lhs + rhs: */
  93 #define ktime_add(lhs, rhs) \
  94                 ({ (ktime_t){ .tv64 = (lhs).tv64 + (rhs).tv64 }; })
  95
  96 /*
  97  * Add a ktime_t variable and a scalar nanosecond value.
  98  * res = kt + nsval:
  99  */
 100 #define ktime_add_ns(kt, nsval) \
 101                 ({ (ktime_t){ .tv64 = (kt).tv64 + (nsval) }; })
 102
 103 /* convert a timespec to ktime_t format: */
 104 static inline ktime_t timespec_to_ktime(struct timespec ts)
 105 {
 106         return ktime_set(ts.tv_sec, ts.tv_nsec);
 107 }
 108
 109 /* convert a timeval to ktime_t format: */
 110 static inline ktime_t timeval_to_ktime(struct timeval tv)
 111 {
 112         return ktime_set(tv.tv_sec, tv.tv_usec * NSEC_PER_USEC);
 113 }
 114
 115 /* Map the ktime_t to timespec conversion to ns_to_timespec function */
 116 #define ktime_to_timespec(kt)           ns_to_timespec((kt).tv64)
 117
 118 /* Map the ktime_t to timeval conversion to ns_to_timeval function */
 119 #define ktime_to_timeval(kt)            ns_to_timeval((kt).tv64)
 120
 121 /* Convert ktime_t to nanoseconds - NOP in the scalar storage format: */
 122 #define ktime_to_ns(kt)                 ((kt).tv64)
 123
 124 #else
 125
 126 /*
 127  * Helper macros/inlines to get the ktime_t math right in the timespec
 128  * representation. The macros are sometimes ugly - their actual use is
 129  * pretty okay-ish, given the circumstances. We do all this for
 130  * performance reasons. The pure scalar nsec_t based code was nice and
 131  * simple, but created too many 64-bit / 32-bit conversions and divisions.
 132  *
 133  * Be especially aware that negative values are represented in a way
 134  * that the tv.sec field is negative and the tv.nsec field is greater
 135  * or equal to zero but less than nanoseconds per second. This is the
 136  * same representation which is used by timespecs.
 137  *
 138  *   tv.sec < 0 and 0 >= tv.nsec < NSEC_PER_SEC
 139  */
 140
 141 /* Set a ktime_t variable to a value in sec/nsec representation: */
 142 static inline ktime_t ktime_set(const long secs, const unsigned long nsecs)
 143 {
 144         return (ktime_t) { .tv = { .sec = secs, .nsec = nsecs } };
 145 }
 146
 147 /**
 148  * ktime_sub - subtract two ktime_t variables
 149  * @lhs:        minuend
 150  * @rhs:        subtrahend
 151  *
 152  * Returns the remainder of the substraction
 153  */
 154 static inline ktime_t ktime_sub(const ktime_t lhs, const ktime_t rhs)
 155 {
 156         ktime_t res;
 157
 158         res.tv64 = lhs.tv64 - rhs.tv64;
 159         if (res.tv.nsec < 0)
 160                 res.tv.nsec += NSEC_PER_SEC;
 161
 162         return res;
 163 }
 164
 165 /**
 166  * ktime_add - add two ktime_t variables
 167  * @add1:       addend1
 168  * @add2:       addend2
 169  *
 170  * Returns the sum of @add1 and @add2.
 171  */
 172 static inline ktime_t ktime_add(const ktime_t add1, const ktime_t add2)
 173 {
 174         ktime_t res;
 175
 176         res.tv64 = add1.tv64 + add2.tv64;
 177         /*
 178          * performance trick: the (u32) -NSEC gives 0x00000000Fxxxxxxx
 179          * so we subtract NSEC_PER_SEC and add 1 to the upper 32 bit.
 180          *
 181          * it's equivalent to:
 182          *   tv.nsec -= NSEC_PER_SEC
 183          *   tv.sec ++;
 184          */
 185         if (res.tv.nsec >= NSEC_PER_SEC)
 186                 res.tv64 += (u32)-NSEC_PER_SEC;
 187
 188         return res;
 189 }
 190
 191 /**
 192  * ktime_add_ns - Add a scalar nanoseconds value to a ktime_t variable
 193  * @kt:         addend
 194  * @nsec:       the scalar nsec value to add
 195  *
 196  * Returns the sum of @kt and @nsec in ktime_t format
 197  */
 198 extern ktime_t ktime_add_ns(const ktime_t kt, u64 nsec);
 199
 200 /**
 201  * timespec_to_ktime - convert a timespec to ktime_t format
 202  * @ts:         the timespec variable to convert
 203  *
 204  * Returns a ktime_t variable with the converted timespec value
 205  */
 206 static inline ktime_t timespec_to_ktime(const struct timespec ts)
 207 {
 208         return (ktime_t) { .tv = { .sec = (s32)ts.tv_sec,
 209                                    .nsec = (s32)ts.tv_nsec } };
 210 }
 211
 212 /**
 213  * timeval_to_ktime - convert a timeval to ktime_t format
 214  * @tv:         the timeval variable to convert
 215  *
 216  * Returns a ktime_t variable with the converted timeval value
 217  */
 218 static inline ktime_t timeval_to_ktime(const struct timeval tv)
 219 {
 220         return (ktime_t) { .tv = { .sec = (s32)tv.tv_sec,
 221                                    .nsec = (s32)tv.tv_usec * 1000 } };
 222 }
 223
 224 /**
 225  * ktime_to_timespec - convert a ktime_t variable to timespec format
 226  * @kt:         the ktime_t variable to convert
 227  *
 228  * Returns the timespec representation of the ktime value
 229  */
 230 static inline struct timespec ktime_to_timespec(const ktime_t kt)
 231 {
 232         return (struct timespec) { .tv_sec = (time_t) kt.tv.sec,
 233                                    .tv_nsec = (long) kt.tv.nsec };
 234 }
 235
 236 /**
 237  * ktime_to_timeval - convert a ktime_t variable to timeval format
 238  * @kt:         the ktime_t variable to convert
 239  *
 240  * Returns the timeval representation of the ktime value
 241  */
 242 static inline struct timeval ktime_to_timeval(const ktime_t kt)
 243 {
 244         return (struct timeval) {
 245                 .tv_sec = (time_t) kt.tv.sec,
 246                 .tv_usec = (suseconds_t) (kt.tv.nsec / NSEC_PER_USEC) };
 247 }
 248
 249 /**
 250  * ktime_to_ns - convert a ktime_t variable to scalar nanoseconds
 251  * @kt:         the ktime_t variable to convert
 252  *
 253  * Returns the scalar nanoseconds representation of @kt
 254  */
 255 static inline s64 ktime_to_ns(const ktime_t kt)
 256 {
 257         return (s64) kt.tv.sec * NSEC_PER_SEC + kt.tv.nsec;
 258 }
 259
 260 #endif
 261
 262 /*
 263  * The resolution of the clocks. The resolution value is returned in
 264  * the clock_getres() system call to give application programmers an
 265  * idea of the (in)accuracy of timers. Timer values are rounded up to
 266  * this resolution values.
 267  */
 268 #define KTIME_LOW_RES           (ktime_t){ .tv64 = TICK_NSEC }
 269
 270 /* Get the monotonic time in timespec format: */
 271 extern void ktime_get_ts(struct timespec *ts);
 272
 273 /* Get the real (wall-) time in timespec format: */
 274 #define ktime_get_real_ts(ts)   getnstimeofday(ts)
 275
 276 #endif