Pileus Git - ~andy/csm213a-hw/blob - hw2/main_time.c

   1 #include <stdint.h>
   2
   3 #include "serial_irq.h"
   4 #include "main_time.h"
   5
   6 /*******************
   7  * Timer functions *
   8  *******************/
   9
  10 uint64_t time_last_local; // timestamp at last time sync
  11 uint64_t time_last_world; // offset at last time sync
  12
  13 /* Initialization */
  14 void time_init(void)
  15 {
  16         // nothing for now
  17 }
  18
  19 /**
  20  * Generate time stamp for an async event:
  21  *   time:  drift compensated wall-clock time
  22  *   stamp: event timestamp from PIT Module
  23  */
  24 uint64_t time_to_world(uint64_t local)
  25 {
  26         uint64_t elapsed = local - time_last_local;
  27         return time_last_world + elapsed;
  28 }
  29
  30 uint64_t time_to_local(uint64_t world)
  31 {
  32         uint64_t elapsed = world - time_last_world;
  33         return time_last_local + elapsed;
  34 }
  35
  36 /**
  37  * Synchronize the timer internal state with updates
  38  * from an external time sync message.
  39  *   local: our internal timestamp for the event
  40  *   world: reference timestamp from the other device
  41  */
  42 void time_ext_init(uint64_t local, uint64_t world)
  43 {
  44         sirq_printf("initialize clocks: %d -> %d\r\n",
  45                         (int)(local/NSEC_PER_SEC),
  46                         (int)(world/NSEC_PER_SEC));
  47
  48         time_last_local = local;
  49         time_last_world = world;
  50 }
  51
  52 /**
  53  * Synchronize the timer internal state with updates
  54  * from an external time sync message.
  55  *   local: our internal timestamp for the event
  56  *   world: reference timestamp from the other device
  57  */
  58 void time_ext_sync(uint64_t local, uint64_t world)
  59 {
  60         uint64_t guess = time_to_world(local);
  61
  62         time_last_local = local;
  63         time_last_world = (guess/2) + (world/2);
  64         //time_last_world = (guess * 3 / 4) + (world * 1 / 4);
  65         //time_last_world =
  66         //      (guess - (        guess / 2)) +
  67         //      (world - (world - world / 2));
  68         //time_last_world =
  69         //      (guess - (guess - guess / 4)) +
  70         //      (world - (        world / 4));
  71
  72         world = time_last_world;
  73
  74 //#ifdef VERBOSE
  75 #if 1
  76         uint64_t error = world > guess ? world - guess :
  77                          guess > world ? guess - world : 0;
  78         int      ahead = guess > world;
  79         sirq_printf("syncing clocks: %6d=%d.%04u -> %d.%04u (err: %s%ld.%09lu)\r\n",
  80                         (int)((local / NSEC_PER_SEC)),
  81                         (int)((guess / NSEC_PER_SEC)),
  82                         (int)((guess % NSEC_PER_SEC)/(NSEC_PER_SEC/10000)),
  83                         (int)((world / NSEC_PER_SEC)),
  84                         (int)((world % NSEC_PER_SEC)/(NSEC_PER_SEC/10000)),
  85                         ahead ? "-" : " ",
  86                         (int32_t )(error / (int64_t)NSEC_PER_SEC),
  87                         (uint32_t)(error % (int64_t)NSEC_PER_SEC));
  88 #endif
  89 //#endif
  90 }
  91
  92 void time_printf(const char *label, uint64_t local)
  93 {
  94         if (local > 1000000 * NSEC_PER_SEC) {
  95                 sirq_printf("%s -- %14s -> %d.%09u\r\n",
  96                                 label, "",
  97                                 (int)(local / NSEC_PER_SEC),
  98                                 (int)(local % NSEC_PER_SEC));
  99         } else {
 100                 uint64_t world = time_to_world(local);
 101                 sirq_printf("%s -- %4d.%09u -> %d.%09u\r\n",
 102                                 label,
 103                                 (int)(local / NSEC_PER_SEC),
 104                                 (int)(local % NSEC_PER_SEC),
 105                                 (int)(world / NSEC_PER_SEC),
 106                                 (int)(world % NSEC_PER_SEC));
 107         }
 108 }