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Date: Tue, 4 Dec 2007 07:13:59 -0600
From: Scott Wood <scottwood@freescale.com>
To: Michael Ellerman <michael@ellerman.id.au>
Subject: Re: [PATCH] Add IPIC MSI interrupt support
Message-ID: <20071204131359.GA5784@loki.buserror.net>
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Cc: linuxppc-dev <linuxppc-dev@ozlabs.org>,
	Gala Kumar <kumar.gala@freescale.com>, Li Tony <Tony.Li@freescale.com>
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On Tue, Dec 04, 2007 at 11:04:18PM +1100, Michael Ellerman wrote:
> On Tue, 2007-12-04 at 18:34 +0800, Li Tony wrote:
> > I am not very sure about spin_lock influence.
> > But maybe somebody will change the virq_to_hw implementation.
> > I will take virq_to_hw instead. 
> 
> I mean the time to take the function call should be pretty small
> compared to taking and releasing a spinlock - but if you have
> performance numbers to prove otherwise let me know :)

I don't think the IPIC is used on any SMP platforms at the moment, so
there's no spinlock overhead other than disabling interrupts...

That said, it's not worth reimplementing to avoid a function call.

-Scott