Re: [PR] sched/clock: call up_timer_gettime() to get higher resolution [nuttx]

[via GitHub]

Fix-Point commented on code in PR #15044:
URL: https://github.com/apache/nuttx/pull/15044#discussion_r1877939827


##########
drivers/timers/arch_alarm.c:
##########
@@ -46,6 +46,7 @@ static FAR struct oneshot_lowerhalf_s *g_oneshot_lower;
 
 #ifndef CONFIG_SCHED_TICKLESS
 static clock_t g_current_tick;
+static clock_t g_base_tick;

Review Comment:
   In order to sync `CLOCK_REALTIME` timer with the `g_system_ticks`, we can 
record the base time here.
    
   ```c
   int clock_systime_timespec(FAR struct timespec *ts)
   {
   #ifdef CONFIG_RTC_HIRES
     if (g_rtc_enabled)
       {
         irqstate_t flags;
   
         up_rtc_gettime(ts);
   
         flags = spin_lock_irqsave(NULL);
         clock_timespec_subtract(ts, &g_basetime, ts);
         spin_unlock_irqrestore(NULL, flags);
       }
     else
       {
         ts->tv_sec = 0;
         ts->tv_nsec = 0;
       }
   #elif defined(CONFIG_SCHED_TICKLESS_TICK_ARGUMENT)
     clock_t ticks = 0;
   
     up_timer_gettick(&ticks);
     clock_ticks2time(ts, ticks);
   #elif defined(CONFIG_SCHED_TICKLESS)
     up_timer_gettime(ts);
   #elif defined(CONFIG_TIMER_ARCH) || \
         defined(CONFIG_ALARM_ARCH)
     static struct timespec base = {0};
     if (!base.tv_sec && !base.tv_nsec)
       {
         up_timer_gettime(&base);
       }
     up_timer_gettime(ts);
     clock_timespec_subtract(ts, &base, ts);
   #else
     clock_ticks2time(ts, g_system_ticks);
   #endif
     return 0;
   }
   ```



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