linux-kernel - Re: [PATCH 01/10] irqchip: irq-mips-gic: export gic_send

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Date:	Thu, 27 Aug 2015 10:22:49 +0800
From:	Jiang Liu <jiang.liu@...ux.intel.com>
To:	Thomas Gleixner <tglx@...utronix.de>,
	Qais Yousef <qais.yousef@...tec.com>
Cc:	Marc Zyngier <marc.zyngier@....com>,
	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	Jason Cooper <jason@...edaemon.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mips@...ux-mips.org" <linux-mips@...ux-mips.org>,
	Mark Rutland <Mark.Rutland@....com>,
	Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH 01/10] irqchip: irq-mips-gic: export gic_send_ipi

On 2015/8/27 5:40, Thomas Gleixner wrote:
> But back to the IPIs. We need infrastructure and DT support to:
> 
> 1) reserve an IPI
> 
> 2) send an IPI
> 
> 3) request/free an IPI
> 
> #1 We have no infrastructure for that, but we definitely need one.
> 
>    We can look at the IPI as a single linux irq number which is
>    replicated on all cpu cores. The replication can happen in hardware
>    or by software, but that depends on the underlying root irq
>    controller. How that is implemented does not matter for the
>    reservation.
> 
>    The most flexible and platform independent solution would be to
>    describe the IPI space as a seperate irq domain. In most cases this
>    would be a hierarchical domain stacked on the root irq domain:
> 
>    [IPI-domain] --> [GIC-MIPS-domain]
> 
>    on x86 this would be:
> 
>    [IPI-domain] --> [vector-domain]
> 
>    That needs some change how the IPIs which are used by the kernel
>    (rescheduling, function call ..) are set up, but we get a proper
>    management and collision avoidance that way. Depending on the
>    platform we could actually remove the whole IPI compile time
>    reservation and hand out IPIs at boot time on demand and
>    dynamically.
Hi Thomas,
	Good point:) That will make the code more clear.
Thanks!
Gerry
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