linux-kernel - Re: [RFC PATCH 1/2] genirq: Add runtime resume/suspend support for IRQ chips

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Date:	Fri, 13 Nov 2015 15:01:45 -0500 (EST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Jon Hunter <jonathanh@...dia.com>
cc:	Kevin Hilman <khilman@...nel.org>,
	Jason Cooper <jason@...edaemon.net>,
	Marc Zyngier <marc.zyngier@....com>,
	Stephen Warren <swarren@...dotorg.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org
Subject: Re: [RFC PATCH 1/2] genirq: Add runtime resume/suspend support for
 IRQ chips

On Fri, 13 Nov 2015, Jon Hunter wrote:
> On 12/11/15 23:20, Kevin Hilman wrote:
> > If all the RPM devices in the domain go idle, it will be powered off
> > independently of the status of the irqchip because the irqchip isn't
> > using RPM. 
> 
> That's dependent on how the irqchip uses these helpers. If these helpers
> invoke RPM then that will not be the case.

You need a very proper description of how that domain is working. If
all devices are idle, it's not necessary correct to power down the
irqchip as is might serve other devices as well.

OTOH, if it can be powered down then all idle devices need to release
the irq they requested because request_irq() would hold a ref on the
power domain.

I have no idea how you can describe that proper.

> > Is there a longer-term plan to handle the irqchips as a "normal" device
> > and use RPM?  IMO, that approach would be helpful even for irqchips that
> > share power domains with CPUs, since there are efforts working towards
> > using genpd/RPM to manage CPUs/clusters.
> 
> That would ideal. However, the majority of irqchips today
> create/register them with IRQCHIP_DECLARE() and not as "normal" devices.
> Therefore, I was reluctant to add "struct device" to the irqchip
> structure. However, if this is what you would prefer and Thomas is ok
> with it, then that would be fine with me.

I have no objections against that, but how is the 'struct device'
going to be initialized?

Thanks,

	tglx
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