linux-kernel - Re: [PATCH] FRV: do_gettimeofday() should no longer use tickadj

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Date:	Fri, 08 Sep 2006 21:05:05 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	David Howells <dhowells@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>, john stultz <johnstul@...ibm.com>,
	Adrian Bunk <bunk@...sta.de>, Andrew Morton <akpm@...l.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	linux-kernel@...r.kernel.org, Jeff Garzik <jeff@...zik.org>,
	netdev@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] FRV: do_gettimeofday() should no longer use tickadj

On Fri, 2006-09-08 at 11:25 +0100, David Howells wrote:
> Benjamin Herrenschmidt <benh@...nel.crashing.org> wrote:
> 
> > No, you do a chain handler. Look at how I do it in
> > arch/powerpc/platform/pseries/setup.c for example. It's actually
> > trivial. You install a special flow handler (which means that there is
> > very little overhead, almost none, from the toplevel irq to the chained
> > irq). You can _also_ if you want just install an IRQ handler for the
> > cascaded controller and call generic_handle_irq (rather than __do_IRQ)
> > from it, but that has more overhead. A chained handler completely
> > relaces the flow handler for the cascade, and thus, if you don't need
> > all of the nits and bits of the other flow handlers for your cascade,
> > you can speed things up by hooking at that level.
> 
> Please update Documentation/DocBook/genericirq.tmpl.  That doesn't mention it.

I must admit I haven't read the documentation :) I looked at the
code/patches when genirq was posted and did my powerpc implementation
based on my understanding of the code and discussions with Thomas and
Ingo. I'll have a look at the doc next week and see if I can improve it.

Cheers,
Ben.


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