Function DELAY

freebsd/mips/ingenic/jz4780_timer.c:271–332

    jz4780_timer_devclass, 0, 0, BUS_PASS_TIMER);

void
DELAY(int usec)
{
	uint32_t counter;
	uint32_t delta, now, previous, remaining;

	/* Timer has not yet been initialized */
	if (jz4780_timer_sc == NULL) {
		for (; usec > 0; usec--)
			for (counter = 200; counter > 0; counter--) {
				/* Prevent gcc from optimizing out the loop */
				mips_rd_cause();
			}
		return;
	}
	TSENTER();

	/*
	 * Some of the other timers in the source tree do this calculation as:
	 *
	 *   usec * ((sc->tc.tc_frequency / 1000000) + 1)
	 *
	 * which gives a fairly pessimistic result when tc_frequency is an exact
	 * multiple of 1000000.  Given the data type and typical values for
	 * tc_frequency adding 999999 shouldn't overflow.
	 */
	remaining = usec * ((jz4780_timer_sc->tc.tc_frequency + 999999) /
	    1000000);

	/*
	 * We add one since the first iteration may catch the counter just
	 * as it is changing.
	 */
	remaining += 1;

	previous = jz4780_get_timecount(&jz4780_timer_sc->tc);

	for ( ; ; ) {
		now = jz4780_get_timecount(&jz4780_timer_sc->tc);

		/*
		 * If the timer has rolled over, then we have the case:
		 *
		 *   if (previous > now) {
		 *     delta = (0 - previous) + now
		 *   }
		 *
		 * which is really no different then the normal case.
		 * Both cases are simply:
		 *
		 *   delta = now - previous.
		 */
		delta = now - previous;

		if (delta >= remaining)
			break;

		previous = now;