Messages in this thread | | | Date | Tue, 10 May 2022 09:16:34 +0100 | From | Marc Zyngier <> | Subject | Re: dmtimer: ack pending interrupt during suspend on am335x/am437x? |
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On 2022-05-09 06:12, Drew Fustini wrote: > Hello Daniel, Tony suggested I mail you along with the list to get > feedback. I'm attempting to upstream these two patches [1][2] from > ti-linux-5.4.y for arch/arm/mach-omap2/timer.c: > 96f4c6e2ba8a ("ARM: OMAP2+: timer: Ack pending interrupt during > suspend") > 7ae7dd5f8272 ("ARM: OMAP2+: timer: Extend pending interrupt ACK for > gic") > > On the TI AM335x and AM437x SoCs, it is possible for a late interrupt > to > be generated which will cause a suspend failure. The first patch makes > omap_clkevt_idle() ack the irq both in the timer peripheral register > and in the interrupt controller to avoid the issue. > > On AM437x only, the GIC cannot be directly acked using only the irqchip > calls. To workaround that, the second patch maps the GIC_CPU_BASE and > reads the GIC_CPU_INTACK register before calling irq_eoi to properly > ack > the late timer interrupts that show up during suspend.
This isn´t an Ack. The Ack happens when you read the IAR register (Interrupt Acknowledgement Register). Writing to EOI performs at least a priority drop, and maybe a deactivation.
Simply writing to EOI doesn´t necessarily solve any problem if the GIC is using EOIMode==1, because you´ĺl miss the deactivation.
> > However, Tony removed most of arch/arm/mach-omap2/timer.c with: > 2ee04b88547a ("ARM: OMAP2+: Drop old timer code for dmtimer and 32k > counter") > > The timers are now implemented in drivers/clocksource/timer-ti-dm.c and > drivers/clocksource/timer-ti-dm-systimer.c. The function > dmtimer_clocksource_suspend() disables the dmtimer and clock but does > not ack any interrupts. > > Tony suggested the right place to ack the interrupt during suspend is > in CPU_CLUSTER_PM_ENTER inside omap_timer_context_notifier(). > > Do you think that would be an acceptable approach?
The real issue is that you are apparently suspending from within an interrupt handler. This is what should be addressed.
Please don´t randomly call into the irqchip code. It will eventually break, and sooner rather than later.
M. -- Jazz is not dead. It just smells funny...
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