linux-kernel - Re: [PATCH 01/15] irqchip/sifive-plic: set max threshold for ignored handlers

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Date:   Tue, 13 Aug 2019 10:44:02 -0700 (PDT)
From:   Paul Walmsley <paul.walmsley@...ive.com>
To:     tglx@...utronix.de, jason@...edaemon.net, maz@...nel.org
cc:     Christoph Hellwig <hch@....de>, Palmer Dabbelt <palmer@...ive.com>,
        Damien Le Moal <damien.lemoal@....com>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/15] irqchip/sifive-plic: set max threshold for ignored
 handlers

Thomas, Jason, Marc,

On Tue, 13 Aug 2019, Christoph Hellwig wrote:

> When running in M-mode we still the S-mode plic handlers in the DT.
> Ignore them by setting the maximum threshold.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>

If you're happy with this, could one of you ack it so we can merge it 
with the rest of this series through the RISC-V tree?

thanks

- Paul

> ---
>  drivers/irqchip/irq-sifive-plic.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
> index cf755964f2f8..c72c036aea76 100644
> --- a/drivers/irqchip/irq-sifive-plic.c
> +++ b/drivers/irqchip/irq-sifive-plic.c
> @@ -244,6 +244,7 @@ static int __init plic_init(struct device_node *node,
>  		struct plic_handler *handler;
>  		irq_hw_number_t hwirq;
>  		int cpu, hartid;
> +		u32 threshold = 0;
>  
>  		if (of_irq_parse_one(node, i, &parent)) {
>  			pr_err("failed to parse parent for context %d.\n", i);
> @@ -266,10 +267,16 @@ static int __init plic_init(struct device_node *node,
>  			continue;
>  		}
>  
> +		/*
> +		 * When running in M-mode we need to ignore the S-mode handler.
> +		 * Here we assume it always comes later, but that might be a
> +		 * little fragile.
> +		 */
>  		handler = per_cpu_ptr(&plic_handlers, cpu);
>  		if (handler->present) {
>  			pr_warn("handler already present for context %d.\n", i);
> -			continue;
> +			threshold = 0xffffffff;
> +			goto done;
>  		}
>  
>  		handler->present = true;
> @@ -279,8 +286,9 @@ static int __init plic_init(struct device_node *node,
>  		handler->enable_base =
>  			plic_regs + ENABLE_BASE + i * ENABLE_PER_HART;
>  
> +done:
>  		/* priority must be > threshold to trigger an interrupt */
> -		writel(0, handler->hart_base + CONTEXT_THRESHOLD);
> +		writel(threshold, handler->hart_base + CONTEXT_THRESHOLD);
>  		for (hwirq = 1; hwirq <= nr_irqs; hwirq++)
>  			plic_toggle(handler, hwirq, 0);
>  		nr_handlers++;
> -- 
> 2.20.1
> 
>