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    Subject[PATCH 5.4 337/355] irqchip/sifive-plic: Fixup EOI failed when masked
    Date
    From: Guo Ren <guoren@linux.alibaba.com>

    commit 69ea463021be0d159ab30f96195fb0dd18ee2272 upstream.

    When using "devm_request_threaded_irq(,,,,IRQF_ONESHOT,,)" in a driver,
    only the first interrupt is handled, and following interrupts are never
    delivered (initially reported in [1]).

    That's because the RISC-V PLIC cannot EOI masked interrupts, as explained
    in the description of Interrupt Completion in the PLIC spec [2]:

    <quote>
    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.
    </quote>

    Re-enable the interrupt before completion if it has been masked during
    the handling, and remask it afterwards.

    [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

    Fixes: bb0fed1c60cc ("irqchip/sifive-plic: Switch to fasteoi flow")
    Reported-by: Vincent Pelletier <plr.vincent@gmail.com>
    Tested-by: Nikita Shubin <nikita.shubin@maquefel.me>
    Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
    Cc: stable@vger.kernel.org
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Palmer Dabbelt <palmer@dabbelt.com>
    Cc: Atish Patra <atish.patra@wdc.com>
    Reviewed-by: Anup Patel <anup@brainfault.org>
    [maz: amended commit message]
    Signed-off-by: Marc Zyngier <maz@kernel.org>
    Link: https://lore.kernel.org/r/20211105094748.3894453-1-guoren@kernel.org
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/irqchip/irq-sifive-plic.c | 8 +++++++-
    1 file changed, 7 insertions(+), 1 deletion(-)

    --- a/drivers/irqchip/irq-sifive-plic.c
    +++ b/drivers/irqchip/irq-sifive-plic.c
    @@ -138,7 +138,13 @@ static void plic_irq_eoi(struct irq_data
    {
    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 = {

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