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SubjectRe: [PATCH v3 0/6] clocksource: rework Atmel TCB timer driver
On 29/03/2018 at 10:01:26 +0200, Alexander Dahl wrote:
> Hei hei,
>
> Am Mittwoch, 28. März 2018, 17:50:33 CEST schrieb Alexandre Belloni:
> > On 28/03/2018 at 17:31:35 +0200, Alexandre Belloni wrote:
> > > > 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.
> >
> > I did mess up.
> >
> > Alexander, can you test that:
>
> Well, I just did.
>
> >
> > diff --git a/drivers/clocksource/timer-atmel-tcb.c
> > b/drivers/clocksource/timer-atmel-tcb.c index 7fde9cfbf203..bbbacf8c46b0
> > 100644
> > --- a/drivers/clocksource/timer-atmel-tcb.c
> > +++ b/drivers/clocksource/timer-atmel-tcb.c
> > @@ -222,7 +222,7 @@ static int __init tc_clkevt_register(struct device_node
> > *node, goto err_slow;
> > clk_disable(tce.clk);
> >
> > - clockevents_config_and_register(&tce.clkevt, 32768, 1, bits - 1);
> > + clockevents_config_and_register(&tce.clkevt, 32768, 1, BIT(bits) - 1);
> >
> > ret = request_irq(tce.irq, tc_clkevt2_irq, IRQF_TIMER | IRQF_SHARED,
> > tce.clkevt.name, &tce);
> >
> > This will behave exactly the same as before on 16bits TCB and will have
> > much less interrupts on 32 bits platforms.
>
> This is the result:
>
> INT NAME RATE MAX
> 17 [vel timer@fffa] 1837 Ints/s (max: 1912)
> 26 [ vel eth0] 3 Ints/s (max: 11)
>
> This is not much lower than the ~2150 I reported yesterday?
>
> I'm sorry I can just test this on at91sam9g20 currently, I have no
> understanding of the subsystem, I can't do a decent review.

Hum, are you sure, I went from:

INT NAME RATE MAX
16 [evel timer@fc0] 1027 Ints/s (max: 1028)
21 [ evel at_xdmac] 3 Ints/s (max: 3)
30 [ evel ttyS0] 2 Ints/s (max: 2)

to:

INT NAME RATE MAX
16 [evel timer@fc0] 6 Ints/s (max: 9)
21 [ evel at_xdmac] 2 Ints/s (max: 2)
30 [ evel ttyS0] 2 Ints/s (max: 2)



--
Alexandre Belloni, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com

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