linux-kernel - Re: [PATCH v2 1/4] genirq: Walk the irq_data hierarchy when resending an interrupt

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Date:   Fri, 04 Sep 2020 20:28:38 +0100
From:   Valentin Schneider <valentin.schneider@....com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Jason Cooper <jason@...edaemon.net>,
        Thomas Gleixner <tglx@...utronix.de>, kernel-team@...roid.com
Subject: Re: [PATCH v2 1/4] genirq: Walk the irq_data hierarchy when resending an interrupt


Hi Marc,

On 03/09/20 19:32, Marc Zyngier wrote:
> On resending an interrupt, we only check the topmost irqchip for
> a irq_retrigger callback. However, this callback could be implemented
> at a lower level. Use irq_chip_retrigger_hierarchy() in this case.
>

Rookie wording question here; re-reading this I'm questioning which way is
up.

>From an irq_data hierarchy PoV, the topmost chip (i.e. last ->parent)
should be the root irqchip. However, the irq_desc we get from irq_to_desc()
ought to hold the irq_data for the lowermost irqchip in that irq_data
hierarchy.

Is it that here by "topmost" you instead mean topmost of the irqchip stack
on top of the root (IOW furthest away from the root)?

> Signed-off-by: Marc Zyngier <maz@...nel.org>
> ---
>  kernel/irq/resend.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/irq/resend.c b/kernel/irq/resend.c
> index c48ce19a257f..8ccd32a0cc80 100644
> --- a/kernel/irq/resend.c
> +++ b/kernel/irq/resend.c
> @@ -86,6 +86,18 @@ static int irq_sw_resend(struct irq_desc *desc)
>  }
>  #endif
>
> +static int try_retrigger(struct irq_desc *desc)
> +{
> +	if (desc->irq_data.chip->irq_retrigger)
> +		return desc->irq_data.chip->irq_retrigger(&desc->irq_data);
> +
> +#ifdef CONFIG_IRQ_DOMAIN_HIERARCHY
> +	return irq_chip_retrigger_hierarchy(&desc->irq_data);
> +#else
> +	return 0;
> +#endif
> +}
> +
>  /*
>   * IRQ resend
>   *
> @@ -113,8 +125,7 @@ int check_irq_resend(struct irq_desc *desc, bool inject)
>
>       desc->istate &= ~IRQS_PENDING;
>
> -	if (!desc->irq_data.chip->irq_retrigger ||
> -	    !desc->irq_data.chip->irq_retrigger(&desc->irq_data))
> +	if (!try_retrigger(desc))
>               err = irq_sw_resend(desc);
>
>       /* If the retrigger was successfull, mark it with the REPLAY bit */