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    On Wed, 14 Dec 2011 19:37:39 +0100
    Jens Rottmann <> wrote:

    > Jens Rottmann schrieb:
    > > Andres Salomon schrieb:
    > >> Just loading cs5535-clockevt should start the periodic timer.
    > >> On my XO-1, IRQ 7 starts firing immediately.
    > > Hmm, no, doesn't work. :-| In /proc/interrupts IRQ 0 gets
    > > increased, not (in my case) IRQ 11.
    > Update: I found that SMP-enabled kernels (like the generic one I was
    > using) do load cs5535-clockevt fine but ignore it and keep using the
    > pit timer instead.

    Note that there are two subsystems at work here; clockevents and
    clocksource. cs5535-clockevt uses clockevents (despite being in
    drivers/clocksource/). For you to switch away from pit (via,
    /sys/devices/system/clocksource/clocksource0/current_clocksource), we'd
    have to implement cs5535_clocksource. Something that would be worth
    doing, but I haven't looked into it..

    > Responsible seems kernel/time/tick-common.c: tick_check_new_device()
    > /*
    > * If the cpu affinity of the device interrupt can not
    > * be set, ignore it.
    > */
    > if (!irq_can_set_affinity(newdev->irq))
    > goto out_bc;
    > Looks like it has been that way for quite some time, maybe
    > cs5535-clockevt hasn't ever worked on SMP kernels.

    I've only ever tested it on UP kernels. I didn't know SMP CS5536
    boards existed. Gosh, I hope all of those cs5535 drivers that hadn't
    had their locking primitives tested aren't racy! ;)

    > If I turn off SMP, cs5535-clockevt replaces the pit timer and the
    > MFGPT IRQ starts firing just as you said - at least on 3.0.9. 3.2-rc5
    > prefers to hang instead, looks like no timer events get generated.
    > Sigh.

    3.2-rc4 hung on my XO-1 due to a bug that's been fixed on rc5, but I
    haven't tested rc5 yet.

    > I'll try to narrow it down tomorrow, but now I'm calling it a day.
    > Cheers
    > Jens

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