linux-kernel - Re: [PATCH V6 2/9] genirq: Look-up trigger type if not specified by caller

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Date:	Mon, 13 Jun 2016 11:42:49 +0100
From:	Marc Zyngier <marc.zyngier@....com>
To:	Jon Hunter <jonathanh@...dia.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>
Cc:	Rob Herring <robh+dt@...nel.org>, Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Stephen Warren <swarren@...dotorg.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Kevin Hilman <khilman@...nel.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Grygorii Strashko <grygorii.strashko@...com>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Linus Walleij <linus.walleij@...aro.org>,
	linux-tegra@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V6 2/9] genirq: Look-up trigger type if not specified by
 caller

On 07/06/16 16:12, Jon Hunter wrote:
> For some devices the IRQ trigger type for a device is read from
> firmware, such as device-tree. The IRQ trigger type is typically read
> when the mapping for IRQ is created, which is before the IRQ is
> requested. Hence, the IRQ trigger type is programmed when mapping the
> IRQ and not when requesting the IRQ.
> 
> Although this works for most cases, in order to support IRQ chips which
> require runtime power management, which may not be accessible prior
> to requesting the IRQ, it is desirable to look-up the IRQ trigger type
> when it is requested. Therefore, if the IRQ trigger type is not
> specified when __setup_irq() is called, look-up the saved IRQ trigger
> type. This will allow us to defer the programming of the trigger type
> from when the IRQ is mapped to when it is actually requested.
> 
> Signed-off-by: Jon Hunter <jonathanh@...dia.com>
> Reviewed-by: Marc Zyngier <marc.zyngier@....com>
> ---
>  kernel/irq/manage.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
> index ef0bc02c3a70..eaedeb74b49d 100644
> --- a/kernel/irq/manage.c
> +++ b/kernel/irq/manage.c
> @@ -1117,6 +1117,13 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
>  	new->irq = irq;
>  
>  	/*
> +	 * If the trigger type is not specified by the caller,
> +	 * then use the default for this interrupt.
> +	 */
> +	if (!(new->flags & IRQF_TRIGGER_MASK))
> +		new->flags |= irqd_get_trigger_type(&desc->irq_data);
> +
> +	/*
>  	 * Check whether the interrupt nests into another interrupt
>  	 * thread.
>  	 */
> 

I've added the following patch to the queue, in order to deal with
percpu interrupts that were not handled by this patch:

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index f8fd1fb..00cfc85 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1751,7 +1751,14 @@ void enable_percpu_irq(unsigned int irq, unsigned int type)
 	if (!desc)
 		return;
 
+	/*
+	 * If the trigger type is not specified by the caller, then
+	 * use the default for this interrupt.
+	 */
 	type &= IRQ_TYPE_SENSE_MASK;
+	if (type == IRQ_TYPE_NONE)
+		type = irqd_get_trigger_type(&desc->irq_data);
+
 	if (type != IRQ_TYPE_NONE) {
 		int ret;
 

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...