arch/tile/kernel/vdso/vgettimeofday.c

   1 /*
   2  * Copyright 2012 Tilera Corporation. All Rights Reserved.
   3  *
   4  *   This program is free software; you can redistribute it and/or
   5  *   modify it under the terms of the GNU General Public License
   6  *   as published by the Free Software Foundation, version 2.
   7  *
   8  *   This program is distributed in the hope that it will be useful, but
   9  *   WITHOUT ANY WARRANTY; without even the implied warranty of
  10  *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
  11  *   NON INFRINGEMENT.  See the GNU General Public License for
  12  *   more details.
  13  */
  14
  15 #define VDSO_BUILD  /* avoid some shift warnings for -m32 in <asm/page.h> */
  16 #include <linux/time.h>
  17 #include <asm/timex.h>
  18 #include <asm/vdso.h>
  19
  20 #if CHIP_HAS_SPLIT_CYCLE()
  21 static inline cycles_t get_cycles_inline(void)
  22 {
  23         unsigned int high = __insn_mfspr(SPR_CYCLE_HIGH);
  24         unsigned int low = __insn_mfspr(SPR_CYCLE_LOW);
  25         unsigned int high2 = __insn_mfspr(SPR_CYCLE_HIGH);
  26
  27         while (unlikely(high != high2)) {
  28                 low = __insn_mfspr(SPR_CYCLE_LOW);
  29                 high = high2;
  30                 high2 = __insn_mfspr(SPR_CYCLE_HIGH);
  31         }
  32
  33         return (((cycles_t)high) << 32) | low;
  34 }
  35 #define get_cycles get_cycles_inline
  36 #endif
  37
  38 /*
  39  * Find out the vDSO data page address in the process address space.
  40  */
  41 inline unsigned long get_datapage(void)
  42 {
  43         unsigned long ret;
  44
  45         /* vdso data page located in the 2nd vDSO page. */
  46         asm volatile ("lnk %0" : "=r"(ret));
  47         ret &= ~(PAGE_SIZE - 1);
  48         ret += PAGE_SIZE;
  49
  50         return ret;
  51 }
  52
  53 int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
  54 {
  55         cycles_t cycles;
  56         unsigned long count, sec, ns;
  57         volatile struct vdso_data *vdso_data;
  58
  59         vdso_data = (struct vdso_data *)get_datapage();
  60         /* The use of the timezone is obsolete, normally tz is NULL. */
  61         if (unlikely(tz != NULL)) {
  62                 while (1) {
  63                         /* Spin until the update finish. */
  64                         count = vdso_data->tz_update_count;
  65                         if (count & 1)
  66                                 continue;
  67
  68                         tz->tz_minuteswest = vdso_data->tz_minuteswest;
  69                         tz->tz_dsttime = vdso_data->tz_dsttime;
  70
  71                         /* Check whether updated, read again if so. */
  72                         if (count == vdso_data->tz_update_count)
  73                                 break;
  74                 }
  75         }
  76
  77         if (unlikely(tv == NULL))
  78                 return 0;
  79
  80         while (1) {
  81                 /* Spin until the update finish. */
  82                 count = vdso_data->tb_update_count;
  83                 if (count & 1)
  84                         continue;
  85
  86                 cycles = (get_cycles() - vdso_data->xtime_tod_stamp);
  87                 ns = (cycles * vdso_data->mult) >> vdso_data->shift;
  88                 sec = vdso_data->xtime_clock_sec;
  89                 ns += vdso_data->xtime_clock_nsec;
  90                 if (ns >= NSEC_PER_SEC) {
  91                         ns -= NSEC_PER_SEC;
  92                         sec += 1;
  93                 }
  94
  95                 /* Check whether updated, read again if so. */
  96                 if (count == vdso_data->tb_update_count)
  97                         break;
  98         }
  99
 100         tv->tv_sec = sec;
 101         tv->tv_usec = ns / 1000;
 102
 103         return 0;
 104 }
 105
 106 int gettimeofday(struct timeval *tv, struct timezone *tz)
 107         __attribute__((weak, alias("__vdso_gettimeofday")));