linux-kernel - Re: [PATCH RFC 1/9] irqchip: gic: Provide support for interrupt grouping

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Date:	Mon, 21 Jul 2014 18:07:00 +0200
From:	Marek Vasut <marex@...x.de>
To:	Daniel Thompson <daniel.thompson@...aro.org>
Cc:	Russell King <linux@....linux.org.uk>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Harro Haan <hrhaan@...il.com>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, patches@...aro.org,
	linaro-kernel@...ts.linaro.org,
	John Stultz <john.stultz@...aro.org>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Christoffer Dall <christoffer.dall@...aro.org>,
	Sricharan R <r.sricharan@...com>
Subject: Re: [PATCH RFC 1/9] irqchip: gic: Provide support for interrupt grouping

On Monday, July 21, 2014 at 04:47:12 PM, Daniel Thompson wrote:
> All GIC hardware except GICv1-without-TrustZone support provides a means
> to group exceptions into group 0 (which can optionally be signally using
> use FIQ) and group 1. The kernel currently provides no means to exploit
> this. This patch alters the initialization of the GIC to place all
> interrupts into group 1 which is the foundational requirement to
> meaningfully use FIQ.

[...]

> @@ -670,7 +753,11 @@ static void gic_raise_softirq(const struct cpumask
> *mask, unsigned int irq) dmb(ishst);
> 
>  	/* this always happens on GIC0 */
> -	writel_relaxed(map << 16 | irq, gic_data_dist_base(&gic_data[0]) +
> GIC_DIST_SOFTINT); +	softint = map << 16 | irq;
> +	if (gic_data_fiq_enable(&gic_data[0]))
> +		softint |= 0x8000;

These magic bits here could use some clarification, possibly a comment.

> +	writel_relaxed(softint,
> +		       gic_data_dist_base(&gic_data[0]) + GIC_DIST_SOFTINT);
> 
>  	raw_spin_unlock_irqrestore(&irq_controller_lock, flags);
>  }
[...]

Best regards,
Marek Vasut
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