Messages in this thread | | | Date | Sun, 31 May 2020 10:33:39 +0100 | From | Marc Zyngier <> | Subject | Re: [PATCH v6 3/6] irqchip: RISC-V per-HART local interrupt controller driver |
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On 2020-05-31 06:36, Anup Patel wrote: > On Sat, May 30, 2020 at 5:31 PM Marc Zyngier <maz@kernel.org> wrote:
[...]
>> > plic_set_threshold(handler, PLIC_DISABLE_THRESHOLD); >> >> Why do you need to both disable the interrupt *and* change the >> priority >> threshold? It seems to be that one of them should be enough, but my >> kno9wledge of the PLIC is limited. In any case, this would deserve a >> comment. > > Okay, I will test and remove "disable the interrupt" part from > plic_dying_cpu().
Be careful, as interrupt enabling/disabling is refcounted in order to allow nesting. If you only enable on CPU_ON and not disable on CPU_OFF, you will end-up with a depth that only increases, up to the point where you hit the roof (it will take a while though).
I would keep the enable/disable as is, and drop the priority setting from the CPU_OFF path.
>> > return 0; >> > @@ -260,7 +266,11 @@ static int plic_starting_cpu(unsigned int cpu) >> > { >> > struct plic_handler *handler = this_cpu_ptr(&plic_handlers); >> > >> > - csr_set(CSR_IE, IE_EIE); >> > + if (plic_parent_irq) >> > + enable_percpu_irq(plic_parent_irq, >> > + irq_get_trigger_type(plic_parent_irq)); >> > + else >> > + pr_warn("cpu%d: parent irq not available\n"); >> >> What does it mean to carry on if the interrupt cannot be signaled? >> Shouldn't you error out instead, and leave the CPU dead? > > The CPU is not dead if we cannot enable RISC-V INTC external > interrupt because the Timer and IPIs interrupts are always through > RISC-V INTC. The PLIC external interrupt not present for a CPU > only means that that CPU cannot receive peripherial interrupts. > > On a sane RISC-V system, if PLIC is present then all CPUs should > be able to get RISC-V INTC external interrupt. Base on this rationale, > I have put a warning for plic_parent_irq == 0.
Fair enough.
M. -- Jazz is not dead. It just smells funny...
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