On 30 June 2016 at 20:01, Dmitry Osipenko <dig...@gmail.com> wrote: > On 30.06.2016 18:02, Peter Maydell wrote: >> What I meant was: ptimer_get_count() is typically called to generate >> a value to return from a register. That's a separate thing, conceptually, >> from whether the device happens to also trigger an interrupt on timer >> expiry by passing a bh to ptimer_init(). So it's very odd for a detail >> of interrupt-on-timer-expiry (that there is a bottom half) to affect >> the value returned when you read the timer count register.
> In order to handle wraparound correctly, software needs to track the moment of > the wraparound - the interrupt. If software reads wrapped around counter value > before IRQ triggered (ptimer expired), then it would assume that no wraparound > happened and won't perform counter value correction, resulting in periodic > counter "jumping" backwards. That just says you need particular behaviour between counter reads and IRQ triggers; it doesn't say that you need the behaviour to be different if the ptimer code doesn't know about the IRQ trigger. thanks -- PMM
