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From:   Anup Patel <anup@brainfault.org>
Date:   Thu, 4 Nov 2021 20:10:42 +0530
Message-ID: <CAAhSdy29qhF4JHuMOqwctn+=HQNBbR3X0gsymqD8OAF1pXE43A@mail.gmail.com>
Subject: Re: [PATCH V6] irqchip/sifive-plic: Fixup EOI failed when masked
To:     Guo Ren <guoren@kernel.org>
Cc:     Atish Patra <atish.patra@wdc.com>, Marc Zyngier <maz@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        "linux-kernel@vger.kernel.org List" <linux-kernel@vger.kernel.org>,
        linux-riscv <linux-riscv@lists.infradead.org>,
        Guo Ren <guoren@linux.alibaba.com>,
        Vincent Pelletier <plr.vincent@gmail.com>,
        Nikita Shubin <nikita.shubin@maquefel.me>
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On Mon, Nov 1, 2021 at 6:47 PM <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 riscv plic couldn't complete masked irq source which has
> been disabled in enable register. The bug was firstly reported in [1].
>
> Here is the description of Interrupt Completion in PLIC spec [2]:
>
> 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.
>
> [1] http://lists.infradead.org/pipermail/linux-riscv/2021-July/007441.html
> [2] https://github.com/riscv/riscv-plic-spec/blob/8bc15a35d07c9edf7b5d23fec9728302595ffc4d/riscv-plic.adoc
>
> Reported-by: Vincent Pelletier <plr.vincent@gmail.com>
> Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> Cc: Anup Patel <anup@brainfault.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Palmer Dabbelt <palmer@dabbelt.com>
> Cc: Atish Patra <atish.patra@wdc.com>
> Cc: Nikita Shubin <nikita.shubin@maquefel.me>
> Cc: incent Pelletier <plr.vincent@gmail.com>

Please include a Fixes: tag

Also, I see that you have dropped the DT bindings patch. We still
need separate compatible string for T-HEAD PLIC because OpenSBI
will use it for other work-arounds.

I suggest to include to more patches in this series:
1) Your latest T-HEAD PLIC DT bindings patch
2) Separate patch to use T-HEAD PLIC compatible in PLIC driver

Regards,
Anup

>
> ---
>
> Changes since V6:
>  - Propagate to plic_irq_eoi for all riscv,plic by Nikita Shubin
>  - Remove thead related codes
>
> Changes since V5:
>  - Move back to mask/unmask
>  - Fixup the problem in eoi callback
>  - Remove allwinner,sun20i-d1 IRQCHIP_DECLARE
>  - Rewrite comment log
>
> Changes since V4:
>  - Update comment by Anup
>
> Changes since V3:
>  - Rename "c9xx" to "c900"
>  - Add sifive_plic_chip and thead_plic_chip for difference
>
> Changes since V2:
>  - Add a separate compatible string "thead,c9xx-plic"
>  - set irq_mask/unmask of "plic_chip" to NULL and point
>    irq_enable/disable of "plic_chip" to plic_irq_mask/unmask
>  - Add a detailed comment block in plic_init() about the
>    differences in Claim/Completion process of RISC-V PLIC and C9xx
>    PLIC.
> ---
>  drivers/irqchip/irq-sifive-plic.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
> index cf74cfa82045..259065d271ef 100644
> --- a/drivers/irqchip/irq-sifive-plic.c
> +++ b/drivers/irqchip/irq-sifive-plic.c
> @@ -163,7 +163,13 @@ static void plic_irq_eoi(struct irq_data *d)
>  {
>         struct plic_handler *handler = this_cpu_ptr(&plic_handlers);
>
> -       writel(d->hwirq, handler->hart_base + CONTEXT_CLAIM);
> +       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);
> +       }
>  }
>
>  static struct irq_chip plic_chip = {
> --
> 2.25.1
>