linux-kernel - Re: [PATCH 1/2] clk: bcm2835: Add AUX interrupt controller

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Date:   Wed, 07 Jun 2017 14:07:32 +0200
From:   Alexander Stein <alexanders83@....de>
To:     linux-kernel@...r.kernel.org
Cc:     Phil Elwell <phil@...pberrypi.org>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Eric Anholt <eric@...olt.net>,
        Stefan Wahren <stefan.wahren@...e.com>,
        devicetree@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-rpi-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/2] clk: bcm2835: Add AUX interrupt controller

On Wednesday 07 June 2017 12:11:45, Phil Elwell wrote:
> Devices in the 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>
> ---
>  drivers/clk/bcm/clk-bcm2835-aux.c | 120
> ++++++++++++++++++++++++++++++++++++++ 1 file changed, 120 insertions(+)
> 
> diff --git a/drivers/clk/bcm/clk-bcm2835-aux.c
> b/drivers/clk/bcm/clk-bcm2835-aux.c index bd750cf..41e0702 100644
> --- a/drivers/clk/bcm/clk-bcm2835-aux.c
> +++ b/drivers/clk/bcm/clk-bcm2835-aux.c
> [...]
> +struct auxirq_state {
> +	void __iomem      *status;
> +	u32                enables;
> +	struct irq_domain *domain;
> +	struct regmap     *local_regmap;
> +};
> +
> +static struct auxirq_state auxirq __read_mostly;
> +
> +static irqreturn_t bcm2835_auxirq_handler(int irq, void *dev_id)
> +{
> +	u32 stat = readl_relaxed(auxirq.status);
> +	u32 masked = stat & auxirq.enables;

Doesn't this hide any spurious interrupts? Is this acceptable? I mean getting 
informed about spurious interrupts seems nice to me, as it indicates a 
hardware/configuration problem.

> +	if (masked & BCM2835_AUXIRQ_UART_MASK)
> +		generic_handle_irq(irq_linear_revmap(auxirq.domain,
> +						     BCM2835_AUXIRQ_UART_IRQ));
> +
> +	if (masked & BCM2835_AUXIRQ_SPI1_MASK)
> +		generic_handle_irq(irq_linear_revmap(auxirq.domain,
> +						     BCM2835_AUXIRQ_SPI1_IRQ));
> +
> +	if (masked & BCM2835_AUXIRQ_SPI2_MASK)
> +		generic_handle_irq(irq_linear_revmap(auxirq.domain,
> +						     BCM2835_AUXIRQ_SPI2_IRQ));
> +
> +	return (masked & BCM2835_AUXIRQ_ALL_MASK) ? IRQ_HANDLED : IRQ_NONE;
> +}

How does interrupt acknowledgement work in these 3 interrupts work?

Best regards,
Alexander