> > - When are interrupts raised. You mention a user specified match value. > > Do we also get an interrupt on wraparound? > > Yes, an interrupts occur on wrap around of the 16 bit timer value. There > are three match registers which correspond to three more > (separately maskable) interrupts which are risen when the timer crosses > that value. My implementation will figure out which of the three events (or > the wraparound) will occur next, and one shot the corresponding period of > time. Note that a match can occur an raise an interrupt without a wrap or > reset occuring. E.G. i could set my timer counting up from 0 and when the > value hits BEEF, i get an interrupt, but the timer still counts all the way > to FFFF before wrapping.
Ok. I'd missed that there are 3 matches per timer. > > If you've got independent wrap and match events then I guess yes, a > > periodic > > wrap plus a oneshot match event is probably appropriate. > > Yes this is the case. I will look into making it happen. It's probably not worth using ptimer at all. Instead use QEMUTimer/qemu_mod_timer directly. The trick is to call qemu_get_clock_ns when the timer is started and calculate all deadlines incrementally from that, not from the time when the last timeout happened to fire. See ptimer.c:ptimer_reload/tick or stellaris.c:gptm_reload/tick for examples. ptimer.c provides a common implementation of a simple periodic timer. Previously we had a dozen different implementations, most of which were broken in one way or annother. For more complicated devices you need to know what you're doing anyway :-) Paul
