linux-kernel - Re: [PATCH v3 3/4] irqchip: Add BCM2835 AUX interrupt controller

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Message-ID: <9e8dcada-2000-e899-2a2c-ab54ae19e3db@raspberrypi.org>
Date:   Tue, 20 Jun 2017 10:19:06 +0100
From:   Phil Elwell <phil@...pberrypi.org>
To:     Florian Fainelli <f.fainelli@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <marc.zyngier@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Stefan Wahren <stefan.wahren@...e.com>,
        Eric Anholt <eric@...olt.net>,
        Russell King <linux@...linux.org.uk>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-rpi-kernel@...ts.infradead.org, linux-clk@...r.kernel.org
Subject: Re: [PATCH v3 3/4] irqchip: Add BCM2835 AUX interrupt controller

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@...pberrypi.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