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Subject: Re: [PATCH v3 3/4] irqchip: Add BCM2835 AUX interrupt controller
To: Florian Fainelli <f.fainelli@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Jason Cooper <jason@lakedaemon.net>,
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        linux-clk@vger.kernel.org
References: <4ceb6c92-f752-180e-6a6e-a94dcd120737@raspberrypi.org>
 <1497457750-35585-1-git-send-email-phil@raspberrypi.org>
 <1497457750-35585-4-git-send-email-phil@raspberrypi.org>
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From: Phil Elwell <phil@raspberrypi.org>
Message-ID: <9e8dcada-2000-e899-2a2c-ab54ae19e3db@raspberrypi.org>
Date: Tue, 20 Jun 2017 10:19:06 +0100
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On 19/06/2017 22:13, Florian Fainelli wrote:
> On 06/14/2017 09:29 AM, Phil Elwell wrote:
>> Devices in the BCM2835 AUX block share a common interrupt line, with a
>> register indicating which devices have active IRQs. Expose this as a
>> nested interrupt controller to avoid IRQ sharing problems (easily
>> observed if UART1 and SPI1/2 are enabled simultaneously).
>>
>> Signed-off-by: Phil Elwell <phil@raspberrypi.org>
>> ---
> 
>> +/*
>> + * The irq_mask and irq_unmask function pointers are used without
>> + * validity checks, so they must not be NULL. Create a dummy function
>> + * with the expected type for use as a no-op.
>> + */
>> +static void bcm2835_aux_irq_dummy(struct irq_data *data)
>> +{
>> +}
>> +
>> +static struct irq_chip bcm2835_aux_irq_chip = {
>> +	.name = "bcm2835-aux_irq",
>> +	.irq_mask = bcm2835_aux_irq_dummy,
>> +	.irq_unmask = bcm2835_aux_irq_dummy,
>> +};
> 
> So how are the interrupt enabled/disabled if this interrupt controller
> just returns their pending state?

Interrupts must be enabled, disabled and acknowledged on the blocks in the
AUX domain - UART1, SPI1 and SPI2. There is no additional masking -
AUXIRQ is essentially an interrupt sharing accelerator.

Phil