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Date:   Tue, 15 Jan 2019 07:54:53 -0800
From:   Christoph Hellwig <hch@infradead.org>
To:     Anup Patel <anup@brainfault.org>
Cc:     Palmer Dabbelt <palmer@sifive.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Jason Cooper <jason@lakedaemon.net>,
        Marc Zyngier <marc.zyngier@arm.com>,
        Christoph Hellwig <hch@infradead.org>,
        Atish Patra <atish.patra@wdc.com>,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 3/5] irqchip: sifive-plic: Add warning in plic_init()
 if handler already present
Message-ID: <20190115155453.GB13095@infradead.org>
References: <20181227111821.80908-1-anup@brainfault.org>
 <20181227111821.80908-4-anup@brainfault.org>
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On Thu, Dec 27, 2018 at 04:48:19PM +0530, Anup Patel wrote:
> We have two enteries (one for M-mode and another for S-mode) in the
> interrupts-extended DT property of PLIC DT node for each HART. It is
> expected that firmware/bootloader will set M-mode HWIRQ line of each
> HART to 0xffffffff (i.e. -1) in interrupts-extended DT property
> because Linux runs in S-mode only.
> 
> If firmware/bootloader is buggy then it will not correctly update
> interrupts-extended DT property which might result in a plic_handler
> configured twice. This patch adds a warning in plic_init() if a
> plic_handler is already marked present. This warning provides us
> a hint about incorrectly updated interrupts-extended DT property.
> 
> Signed-off-by: Anup Patel <anup@brainfault.org>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> ---
>  drivers/irqchip/irq-sifive-plic.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
> index 01bbbbffbcae..b9a0bcefe426 100644
> --- a/drivers/irqchip/irq-sifive-plic.c
> +++ b/drivers/irqchip/irq-sifive-plic.c
> @@ -229,6 +229,11 @@ static int __init plic_init(struct device_node *node,
>  
>  		cpu = riscv_hartid_to_cpuid(hartid);
>  		handler = per_cpu_ptr(&plic_handlers, cpu);
> +		if (handler->present) {
> +			pr_warn("handler already present for context %d.\n", i);
> +			continue;
> +		}
> +

Just use WARN_ON_ONCE?