Re: [PATCH v4 3/5] ARM: tegra: Initialize interrupt controller from DT

[Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>]

On Friday 29 August 2014 17:04:28 Thierry Reding wrote:
>         static struct irq_chip *extn;
> 
>         void gic_arch_register(const struct irqchip *chip)
>         {
>                 if (WARN(extn != NULL))
>                         return;
> 
>                 gic_chip.flags |= chip->flags;
>                 extn = chip;
>         }
> 
> Any preferences, or other ideas? Adding Thomas and Jason, perhaps they
> can provide more input on how to solve this.

I think the entire gic_arch_extn method is done in a rather odd way
and we should try to come up with a replacement.

These are the users at the moment:

arch/arm/mach-exynos/pm.c:      gic_arch_extn.irq_set_wake = exynos_irq_set_wake;
arch/arm/mach-imx/gpc.c:        gic_arch_extn.irq_mask = imx_gpc_irq_mask;
arch/arm/mach-imx/gpc.c:        gic_arch_extn.irq_unmask = imx_gpc_irq_unmask;
arch/arm/mach-imx/gpc.c:        gic_arch_extn.irq_set_wake = imx_gpc_irq_set_wake;
arch/arm/mach-omap2/omap-wakeupgen.c:   gic_arch_extn.irq_mask = wakeupgen_mask;
arch/arm/mach-omap2/omap-wakeupgen.c:   gic_arch_extn.irq_unmask = wakeupgen_unmask;
arch/arm/mach-omap2/omap-wakeupgen.c:   gic_arch_extn.flags = IRQCHIP_MASK_ON_SUSPEND | IRQCHIP_SKIP_SET_W
arch/arm/mach-shmobile/intc-sh73a0.c:   gic_arch_extn.irq_set_wake = sh73a0_set_wake;
arch/arm/mach-shmobile/setup-r8a7779.c: gic_arch_extn.irq_set_wake = r8a7779_set_wake;
arch/arm/mach-tegra/irq.c:      gic_arch_extn.irq_ack = tegra_ack;
arch/arm/mach-tegra/irq.c:      gic_arch_extn.irq_eoi = tegra_eoi;
arch/arm/mach-tegra/irq.c:      gic_arch_extn.irq_mask = tegra_mask;
arch/arm/mach-tegra/irq.c:      gic_arch_extn.irq_unmask = tegra_unmask;
arch/arm/mach-tegra/irq.c:      gic_arch_extn.irq_retrigger = tegra_retrigger;
arch/arm/mach-tegra/irq.c:      gic_arch_extn.irq_set_wake = tegra_set_wake;
arch/arm/mach-tegra/irq.c:      gic_arch_extn.flags = IRQCHIP_MASK_ON_SUSPEND;
arch/arm/mach-ux500/cpu.c:      gic_arch_extn.flags = IRQCHIP_SKIP_SET_WAKE | IRQCHIP_MASK_ON_SUSPEND;
arch/arm/mach-zynq/common.c:    gic_arch_extn.flags = IRQCHIP_SKIP_SET_WAKE | IRQCHIP_MASK_ON_SUSPEND;

I have to admit I don't really understand how these work, but what
I'd expect to work better is a way to turn the gic code into more
of a library that can be used by specialized drivers. In that
case you would register a driver for the tegra gic using IRQCHIP_DECLARE
and that driver would call a variation of gic_of_init() or gic_init_bases()
with the extra stuff as arguments.

We'd have to hack around the fact that all these platforms currently
don't list a specialized compatible string, but at least for the future
we should be able to do this without special hacks.

	Arnd