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                       (~((u64)1 << 63))
  60
  61 /*
  62  * ktime_t definitions when using the 64-bit scalar representation:
  63  */
  64
  65 #if (BITS_PER_LONG == 64) || defined(CONFIG_KTIME_SCALAR)
  66
  67 /**
  68  * ktime_set - Set a ktime_t variable from a seconds/nanoseconds value
  69  *
  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         return (ktime_t) { .tv64 = (s64)secs * NSEC_PER_SEC + (s64)nsecs };
  78 }
  79
  80 /* Subtract two ktime_t variables. rem = lhs -rhs: */
  81 #define ktime_sub(lhs, rhs) \
  82                 ({ (ktime_t){ .tv64 = (lhs).tv64 - (rhs).tv64 }; })
  83
  84 /* Add two ktime_t variables. res = lhs + rhs: */
  85 #define ktime_add(lhs, rhs) \
  86                 ({ (ktime_t){ .tv64 = (lhs).tv64 + (rhs).tv64 }; })
  87
  88 /*
  89  * Add a ktime_t variable and a scalar nanosecond value.
  90  * res = kt + nsval:
  91  */
  92 #define ktime_add_ns(kt, nsval) \
  93                 ({ (ktime_t){ .tv64 = (kt).tv64 + (nsval) }; })
  94
  95 /* convert a timespec to ktime_t format: */
  96 static inline ktime_t timespec_to_ktime(struct timespec ts)
  97 {
  98         return ktime_set(ts.tv_sec, ts.tv_nsec);
  99 }
 100
 101 /* convert a timeval to ktime_t format: */
 102 static inline ktime_t timeval_to_ktime(struct timeval tv)
 103 {
 104         return ktime_set(tv.tv_sec, tv.tv_usec * NSEC_PER_USEC);
 105 }
 106
 107 /* Map the ktime_t to timespec conversion to ns_to_timespec function */
 108 #define ktime_to_timespec(kt)           ns_to_timespec((kt).tv64)
 109
 110 /* Map the ktime_t to timeval conversion to ns_to_timeval function */
 111 #define ktime_to_timeval(kt)            ns_to_timeval((kt).tv64)
 112
 113 /* Convert ktime_t to nanoseconds - NOP in the scalar storage format: */
 114 #define ktime_to_ns(kt)                 ((kt).tv64)
 115
 116 #else
 117
 118 /*
 119  * Helper macros/inlines to get the ktime_t math right in the timespec
 120  * representation. The macros are sometimes ugly - their actual use is
 121  * pretty okay-ish, given the circumstances. We do all this for
 122  * performance reasons. The pure scalar nsec_t based code was nice and
 123  * simple, but created too many 64-bit / 32-bit conversions and divisions.
 124  *
 125  * Be especially aware that negative values are represented in a way
 126  * that the tv.sec field is negative and the tv.nsec field is greater
 127  * or equal to zero but less than nanoseconds per second. This is the
 128  * same representation which is used by timespecs.
 129  *
 130  *   tv.sec < 0 and 0 >= tv.nsec < NSEC_PER_SEC
 131  */
 132
 133 /* Set a ktime_t variable to a value in sec/nsec representation: */
 134 static inline ktime_t ktime_set(const long secs, const unsigned long nsecs)
 135 {
 136         return (ktime_t) { .tv = { .sec = secs, .nsec = nsecs } };
 137 }
 138
 139 /**
 140  * ktime_sub - subtract two ktime_t variables
 141  *
 142  * @lhs:        minuend
 143  * @rhs:        subtrahend
 144  *
 145  * Returns the remainder of the substraction
 146  */
 147 static inline ktime_t ktime_sub(const ktime_t lhs, const ktime_t rhs)
 148 {
 149         ktime_t res;
 150
 151         res.tv64 = lhs.tv64 - rhs.tv64;
 152         if (res.tv.nsec < 0)
 153                 res.tv.nsec += NSEC_PER_SEC;
 154
 155         return res;
 156 }
 157
 158 /**
 159  * ktime_add - add two ktime_t variables
 160  *
 161  * @add1:       addend1
 162  * @add2:       addend2
 163  *
 164  * Returns the sum of addend1 and addend2
 165  */
 166 static inline ktime_t ktime_add(const ktime_t add1, const ktime_t add2)
 167 {
 168         ktime_t res;
 169
 170         res.tv64 = add1.tv64 + add2.tv64;
 171         /*
 172          * performance trick: the (u32) -NSEC gives 0x00000000Fxxxxxxx
 173          * so we subtract NSEC_PER_SEC and add 1 to the upper 32 bit.
 174          *
 175          * it's equivalent to:
 176          *   tv.nsec -= NSEC_PER_SEC
 177          *   tv.sec ++;
 178          */
 179         if (res.tv.nsec >= NSEC_PER_SEC)
 180                 res.tv64 += (u32)-NSEC_PER_SEC;
 181
 182         return res;
 183 }
 184
 185 /**
 186  * ktime_add_ns - Add a scalar nanoseconds value to a ktime_t variable
 187  *
 188  * @kt:         addend
 189  * @nsec:       the scalar nsec value to add
 190  *
 191  * Returns the sum of kt and nsec in ktime_t format
 192  */
 193 extern ktime_t ktime_add_ns(const ktime_t kt, u64 nsec);
 194
 195 /**
 196  * timespec_to_ktime - convert a timespec to ktime_t format
 197  *
 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  *
 211  * @tv:         the timeval variable to convert
 212  *
 213  * Returns a ktime_t variable with the converted timeval value
 214  */
 215 static inline ktime_t timeval_to_ktime(const struct timeval tv)
 216 {
 217         return (ktime_t) { .tv = { .sec = (s32)tv.tv_sec,
 218                                    .nsec = (s32)tv.tv_usec * 1000 } };
 219 }
 220
 221 /**
 222  * ktime_to_timespec - convert a ktime_t variable to timespec format
 223  *
 224  * @kt:         the ktime_t variable to convert
 225  *
 226  * Returns the timespec representation of the ktime value
 227  */
 228 static inline struct timespec ktime_to_timespec(const ktime_t kt)
 229 {
 230         return (struct timespec) { .tv_sec = (time_t) kt.tv.sec,
 231                                    .tv_nsec = (long) kt.tv.nsec };
 232 }
 233
 234 /**
 235  * ktime_to_timeval - convert a ktime_t variable to timeval format
 236  *
 237  * @kt:         the ktime_t variable to convert
 238  *
 239  * Returns the timeval representation of the ktime value
 240  */
 241 static inline struct timeval ktime_to_timeval(const ktime_t kt)
 242 {
 243         return (struct timeval) {
 244                 .tv_sec = (time_t) kt.tv.sec,
 245                 .tv_usec = (suseconds_t) (kt.tv.nsec / NSEC_PER_USEC) };
 246 }
 247
 248 /**
 249  * ktime_to_ns - convert a ktime_t variable to scalar nanoseconds
 250  * @kt:         the ktime_t variable to convert
 251  *
 252  * Returns the scalar nanoseconds representation of kt
 253  */
 254 static inline u64 ktime_to_ns(const ktime_t kt)
 255 {
 256         return (u64) kt.tv.sec * NSEC_PER_SEC + kt.tv.nsec;
 257 }
 258
 259 #endif
 260
 261 /*
 262  * The resolution of the clocks. The resolution value is returned in
 263  * the clock_getres() system call to give application programmers an
 264  * idea of the (in)accuracy of timers. Timer values are rounded up to
 265  * this resolution values.
 266  */
 267 #define KTIME_REALTIME_RES      (ktime_t){ .tv64 = TICK_NSEC }
 268 #define KTIME_MONOTONIC_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