Messages in this thread | | | Date | Thu, 28 Oct 2021 15:58:19 +0100 | From | Marc Zyngier <> | Subject | Re: [PATCH V5 3/3] irqchip/sifive-plic: Fixup thead, c900-plic request_threaded_irq with ONESHOT |
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On Thu, 28 Oct 2021 11:55:23 +0100, Nikita Shubin <nikita.shubin@maquefel.me> wrote: > > Hello Marc and Guo Ren! > > On Mon, 25 Oct 2021 11:48:33 +0100 > Marc Zyngier <maz@kernel.org> wrote: > > > On Sun, 24 Oct 2021 02:33:03 +0100, > > guoren@kernel.org wrote: > > > > > > From: Guo Ren <guoren@linux.alibaba.com> > > > > > > When using "devm_request_threaded_irq(,,,,IRQF_ONESHOT,,)" in the > > > driver, only the first interrupt could be handled, and continue irq > > > is blocked by hw. Because the thead,c900-plic couldn't complete > > > masked irq source which has been disabled in enable register. Add > > > thead_plic_chip which fix up c906-plic irq source completion > > > problem by unmask/mask wrapper. > > > > > > Here is the description of Interrupt Completion in PLIC spec [1]: > > > > > > The PLIC signals it has completed executing an interrupt handler by > > > writing the interrupt ID it received from the claim to the > > > claim/complete register. The PLIC does not check whether the > > > completion ID is the same as the last claim ID for that target. If > > > the completion ID does not match an interrupt source that is > > > currently enabled for the target, the ^^ ^^^^^^^^^ ^^^^^^^ > > > completion is silently ignored. > > > > Given this bit of the spec... > > > > > +static void plic_thead_irq_eoi(struct irq_data *d) > > > +{ > > > + struct plic_handler *handler = > > > this_cpu_ptr(&plic_handlers); + > > > + if (irqd_irq_masked(d)) { > > > + plic_irq_unmask(d); > > > + writel(d->hwirq, handler->hart_base + > > > CONTEXT_CLAIM); > > > + plic_irq_mask(d); > > > + } else { > > > + writel(d->hwirq, handler->hart_base + > > > CONTEXT_CLAIM); > > > + } > > > +} > > > + > > > > ... it isn't obvious to me why this cannot happen on an SiFive PLIC. > > This indeed happens with SiFive PLIC. I am currently tinkering with > da9063 RTC on SiFive Unmatched, and ALARM irq fires only once. However > with changes proposed by Guo Ren in plic_thead_irq_eoi, everything > begins to work fine. > > May be these change should be propagated to plic_irq_eoi instead of > making a new function ?
That's my impression too. I think the T-Head defect is pretty much immaterial when you consider how 'interesting' the PLIC architecture is. Conflating EOI and masking really is a misfeature...
M.
-- Without deviation from the norm, progress is not possible.
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