Re: [PATCH v8 02/10] irqchip/riscv-intc: Allow large non-standard interrupt number

From: Thomas Gleixner <tglx@linutronix.de>
To: Yu Chien Peter Lin <peterlin@andestech.com>,
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Cc: Randolph <randolph@andestech.com>, Atish Patra <atishp@rivosinc.com>
Subject: Re: [PATCH v8 02/10] irqchip/riscv-intc: Allow large non-standard interrupt number
Date: Tue, 13 Feb 2024 11:04:53 +0100	[thread overview]
Message-ID: <877cj8issa.ffs@tglx> (raw)
In-Reply-To: <20240129092553.2058043-3-peterlin@andestech.com>

On Mon, Jan 29 2024 at 17:25, Yu Chien Peter Lin wrote:
>  static asmlinkage void riscv_intc_irq(struct pt_regs *regs)
>  {
>  	unsigned long cause = regs->cause & ~CAUSE_IRQ_FLAG;
>  
> -	if (unlikely(cause >= BITS_PER_LONG))
> -		panic("unexpected interrupt cause");
> -
> -	generic_handle_domain_irq(intc_domain, cause);
> +	if (generic_handle_domain_irq(intc_domain, cause))
> +		pr_warn_ratelimited("Failed to handle interrupt (cause: %ld)\n",
> +				    cause);

Either let the cause stick out or you need brackets. See:

  https://www.kernel.org/doc/html/latest/process/maintainer-tip.html#bracket-rules

>  }
>  
>  /*
> @@ -93,6 +95,14 @@ static int riscv_intc_domain_alloc(struct irq_domain *domain,
>  	if (ret)
>  		return ret;
>  
> +	/*
> +	 * Only allow hwirq for which we have corresponding standard or
> +	 * custom interrupt enable register.
> +	 */
> +	if ((riscv_intc_nr_irqs <= hwirq && hwirq < riscv_intc_custom_base) ||
> +	    (riscv_intc_custom_base + riscv_intc_custom_nr_irqs) <= hwirq)
> +		return -EINVAL;

Duh. This mix of ordering required to read this 3 times. What's wrong
with writing this consistently:

	if ((hwirq >= riscv_intc_nr_irqs && hwirq < riscv_intc_custom_base) ||
	    (hwirq >= iscv_intc_custom_base + riscv_intc_custom_nr_irqs)
		return -EINVAL;

Hmm?

> -	pr_info("%d local interrupts mapped\n", BITS_PER_LONG);
> +	pr_info("%d local interrupts mapped\n", riscv_intc_nr_irqs);
> +	if (riscv_intc_custom_nr_irqs)
> +		pr_info("%d custom local interrupts mapped\n",
> +			riscv_intc_custom_nr_irqs);

See bracket rules.

>  	return 0;
>  }
> @@ -166,6 +178,10 @@ static int __init riscv_intc_init(struct device_node *node,
>  		return 0;
>  	}
>  
> +	riscv_intc_nr_irqs = BITS_PER_LONG;
> +	riscv_intc_custom_base = riscv_intc_nr_irqs;

Why don't you initialize the static variables with constants right away?

> +	riscv_intc_custom_nr_irqs = 0;

It's already 0, no?

>  	return riscv_intc_init_common(of_node_to_fwnode(node));
>  }

Thanks,

        tglx