drivers/timers/arch_alarm.c: Remove ndelay_accurate

Using ONESHOT_CURRENT retrieves the tick number multiplied by tick time; thus
it doesn't give the accurate monotonic time - it is quantized by
the tick time. This cannot be used as a ndelay timer, it would always loop
at least to the end of the ongoing tick.

Revert the up_udelay to use the original "coarse" looping. The "accurate" udelay,
if such is needed, should either be done under arch specific code, or there should be
a function for getting the accurate time that is available for all the platforms.

Signed-off-by: Jukka Laitinen <jukkax@ssrc.tii.ae>

drivers/timers/arch_alarm.c

@@ -50,22 +50,6 @@ static clock_t g_current_tick;
  * Private Functions
  ****************************************************************************/
 
-static void ndelay_accurate(unsigned long nanoseconds)
-{
-  struct timespec now;
-  struct timespec end;
-  struct timespec delta;
-
-  ONESHOT_CURRENT(g_oneshot_lower, &now);
-  clock_nsec2time(&delta, nanoseconds);
-  clock_timespec_add(&now, &delta, &end);
-
-  while (clock_timespec_compare(&now, &end) < 0)
-    {
-      ONESHOT_CURRENT(g_oneshot_lower, &now);
-    }
-}
-
 static void udelay_coarse(useconds_t microseconds)
 {
   volatile int i;
@@ -441,13 +425,6 @@ void weak_function up_udelay(useconds_t microseconds)
  ****************************************************************************/
 
 void weak_function up_ndelay(unsigned long nanoseconds)
-{
-  if (g_oneshot_lower != NULL)
-    {
-      ndelay_accurate(nanoseconds);
-    }
-  else /* Oneshot timer hasn't been initialized yet */
 {
   udelay_coarse((nanoseconds + NSEC_PER_USEC - 1) / NSEC_PER_USEC);
 }
-}