On Tue, Aug 25, 2020 at 11:33:53AM +0200, Kurt Kanzenbach wrote: > On Tue Aug 25 2020, Vladimir Oltean wrote: > > On Thu, Aug 20, 2020 at 10:11:15AM +0200, Kurt Kanzenbach wrote: > > > > Explain again how this works, please? The hrtimer measures the CLOCK_TAI > > of the CPU, but you are offloading the CLOCK_TAI domain of the NIC? So > > you are assuming that the CPU and the NIC PHC are synchronized? What if > > they aren't? > > Yes, I assume that's synchronized with e.g. phc2sys. > My intuition tells me that this isn't the user's expectation, and that it should do the right thing even if it's not synchronized to the system clock. > > > > And what if the base-time is in the past, do you deal with that (how > > does the hardware deal with a base-time in the past)? > > A base-time in the past (example: 0) should work: you should advance the > > base-time into the nearest future multiple of the cycle-time, to at > > least preserve phase correctness of the schedule. > > If the hrtimer is programmed with a value in the past, it fires > instantly. Yes, it does. > The callback is executed and the start time is programmed. > With a valid value from the hardware's perspective? Thanks, -Vladimir
