Messages in this thread | | | Date | Wed, 28 Mar 2018 17:31:35 +0200 | From | Alexandre Belloni <> | Subject | Re: [PATCH v3 0/6] clocksource: rework Atmel TCB timer driver |
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On 28/03/2018 at 16:36:34 +0200, Daniel Lezcano wrote: > On 28/03/2018 16:16, Alexandre Belloni wrote: > > On 28/03/2018 at 15:03:11 +0200, Daniel Lezcano wrote: > >> On 28/03/2018 12:29, Alexander Dahl wrote: > >>> Hello Daniel, > >>> > >>> Am Dienstag, 27. März 2018, 13:30:22 CEST schrieb Daniel Lezcano: > >>>> Can you can give a rough amount for the irq rate on the timer ? > >>> > >>> I used itop [1] now to get a rough estimate. First with kernel v4.14.29-rt25 > >>> (fully preempt RT): > >>> > >>> INT NAME RATE MAX > >>> 19 [ vel tc_clkevt] 397 Ints/s (max: 432) > >>> 26 [ vel eth0] 4 Ints/s (max: 38) > >>> > >>> Next test with kernel v4.15.13 gives (slightly slower, but non-RT): > >>> > >>> INT NAME RATE MAX > >>> 19 [ vel tc_clkevt] 248 Ints/s (max: 273) > >>> 26 [ vel eth0] 4 Ints/s (max: 11) > >>> > >>> With kernel v4.16-rc7 plus this patch series and tcb as clocksource: > >>> > >>> INT NAME RATE MAX > >>> 17 [vel timer@fffa] 2164 Ints/s (max: 2183) > >>> 26 [ vel eth0] 5 Ints/s (max: 10) > >>> > >>> Is this the information you wanted? If not, could you point me on how to get > >>> the requested irq rate? > >> > >> It is perfect. Thanks! > >> > >> It confirms what I was worried about: the clocksource wraps up too > >> quickly thus raising an interrupt every 400us. That is why I asked > >> Alexande about a prescalar register. > >> > > > > The code should behave exactly the same between the previous and the new > > driver. The interrupt is not coming from the clocksource but from the > > clockevent and it is already on the slowest clock, the 32kHz one. > > Do you have an explanation of why the rate is much higher ? >
The core is giving deltas of 31 clocks instead of much more than that, I guess I messed up the initialization somewhere.
-- Alexandre Belloni, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering https://bootlin.com
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