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 12:09:11 +0100
From:	Jon Hunter <jonathanh@...dia.com>
To:	Marc Zyngier <marc.zyngier@....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 13/06/16 11:42, Marc Zyngier wrote:
> 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);
> +

I am wondering if you need this here because now __setup_irq(), called
by request_percpu_irq(), will actually look-up the saved type even for a
percpu-irq. So shouldn't this already be handled? Or am I missing something?

Cheers
Jon

-- 
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