Messages in this thread | | | Date | Thu, 12 Oct 2017 22:53:09 +0200 (CEST) | From | David Kozub <> | Subject | Re: PROBLEM: Kernel BUG in mfgpt_tick (cs5535-clockevt.c) on ALIX 2c3 - null call |
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On Thu, 12 Oct 2017, Thomas Gleixner wrote:
> On Thu, 12 Oct 2017, Daniel Lezcano wrote: > >> On 11/10/2017 22:48, David Kozub wrote: >> >> [ ... ] >> >>>> >>>> + disable_timer(timer); >>>> + cs5535_mfgpt_write(timer, MFGPT_REG_COUNTER, 0); >>>> + >>>> /* Set up the IRQ on the MFGPT side */ >>>> if (cs5535_mfgpt_setup_irq(timer, MFGPT_CMP2, &timer_irq)) { >>>> printk(KERN_ERR DRV_NAME ": Could not set up IRQ %d\n", >>> >>> I tried that and the handler is still called. So I did some more random >>> experiments and I found out that if I call disable_timer(timer) twice, >>> then the issue is resolved (the handler is not called before the >>> registration is finished.) And I don't have to set MFGPT_REG_COUNTER to 0. >> >> Aha! we are close to a fix. >> >>> I have no idea why do I have to call disable_timer twice. >> >> For testing purpose, can you try by adding mmiowb() and/or wmb() after >> disable_timer()?
I tried one, the other, both. Still, the unexpected handler call happens. I (again) added a msleep(1000) after the disable (and the barriers). If the trouble was a missing barrier, the sleep would most likely also make the isaue go away (even if in a hacky way).
> The real question is why > > /* Set the clock scale and enable the event mode for CMP2 */ > val = MFGPT_SCALE | (3 << 8); > > cs5535_mfgpt_write(cs5535_event_clock, MFGPT_REG_SETUP, val); > > is in the setup code at all. > > The obvious place for this is in mfgpt_set_periodic() which gets called > when the clock event and the handler is set up in the core code. Up to that > point the interrupt handler is protected against shared interrupts via the > is_shutdown() check.
It is, but only after clockevents_config_and_register. But mfgpt_tick is called before that (just after setup_irq).
Best regards, David | |