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Re: [PATCH] JAZZ: disable PIT; cleanup R4030 clockevent

To: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Subject: Re: [PATCH] JAZZ: disable PIT; cleanup R4030 clockevent
From: Ralf Baechle <ralf@linux-mips.org>
Date: Sun, 4 Nov 2007 00:33:38 +0000
Cc: linux-mips@linux-mips.org
In-reply-to: <20071102220819.GA20792@alpha.franken.de>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20071101125236.GA16577@alpha.franken.de> <20071101150741.GA8570@linux-mips.org> <20071101160210.GA20366@linux-mips.org> <20071102101713.GA9110@alpha.franken.de> <20071102122001.GC22829@linux-mips.org> <20071102220819.GA20792@alpha.franken.de>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Mutt/1.5.14 (2007-02-12)
On Fri, Nov 02, 2007 at 11:08:19PM +0100, Thomas Bogendoerfer wrote:

> On Fri, Nov 02, 2007 at 12:20:01PM +0000, Ralf Baechle wrote:
> > One thing I'm still wondering about, does the kernel actually go tickless
> > for you?
> 
> a kernel with CONFIG_NO_HZ boots and acts normal. But it looks like
> the PIT is still ticking at the selected 100HZ...

I think this happens because the R4030 clockevent device has a rather
high rating of 300 while the PIT because of an omission or intension
doesn't set it's rating at all so has rating of 0.  So Linux prefers the
R4030.  You can see which clockevent device is actually getting used
by Linux in /proc/timer_list.

  Ralf

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