Messages in this thread | | | From | Anup Patel <> | Date | Sat, 30 Oct 2021 15:57:16 +0530 | Subject | Re: [PATCH V5 3/3] irqchip/sifive-plic: Fixup thead, c900-plic request_threaded_irq with ONESHOT |
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On Thu, Oct 28, 2021 at 8:28 PM Marc Zyngier <maz@kernel.org> wrote: > > 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...
Unfortunately, the PLIC implementation is the same across existing boards (except T-HEAD) so this issue is there on all existing boards.
I double checked the upcoming RISC-V AIA specification and this problem is not there in RISC-V AIA because the interrupt claim/completion is different. (Refer, https://github.com/riscv/riscv-aia/releases/download/0.2-draft.27/riscv-interrupts-027.pdf)
I plan to send-out RFC PATCH for AIA soon so that we get early feedback from everyone on LKML.
Regards, Anup
> > M. > > -- > Without deviation from the norm, progress is not possible.
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