Subject: Re: [PATCH 2.6.21-rt2] PowerPC: decrementer clockevent driver
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: Dave Liu <r63238@freescale.com>, linuxppc-dev@ozlabs.org,
       tglx@linutronix.de, mingo@elte.hu, linux-kernel@vger.kernel.org
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Date: Sat, 19 May 2007 09:27:52 +1000
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On Fri, 2007-05-18 at 17:41 +0400, Sergei Shtylyov wrote:
>     From the "PowerPC Operating Environment Architecture" that I've
> already 
> quoated t follows that POWER4-compatible decremented exception *must*
> be edge 
> triggered.
> 
> > says that an exception is generated when the MSB transitions from 0
> to
> > 1. It's not clear wether the exception sticks while that bit is 1 or
> is
> 
>     Freescale MPC 7450 manual says the same, for example. 

I find it extremely silly to implement it as edge anyway. The EE line is
level triggered, and having a mix of edge and level on the same
exception without a clean way to retrigger the DEC one other than
waiting one tick is just causing trouble.

Ben.


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