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Date: Wed, 22 Jun 2005 18:22:50 +0100
From: Russell King <rmk+lkml@arm.linux.org.uk>
To: Daniel Walker <dwalker@mvista.com>
Cc: "Eugeny S. Mints" <emints@ru.mvista.com>,
       Andrew Lewis <andrew-lewis@netspace.net.au>,
       linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>
Subject: Re: ARM Linux Suitability for Real-time Application
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	"Eugeny S. Mints" <emints@ru.mvista.com>,
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References: <20050622100231.A28181@flint.arm.linux.org.uk> <Pine.LNX.4.10.10506220951190.455-100000@godzilla.mvista.com>
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In-Reply-To: <Pine.LNX.4.10.10506220951190.455-100000@godzilla.mvista.com>; from dwalker@mvista.com on Wed, Jun 22, 2005 at 09:52:40AM -0700
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On Wed, Jun 22, 2005 at 09:52:40AM -0700, Daniel Walker wrote:
> On Wed, 22 Jun 2005, Russell King wrote:
> > If you're just after some background process to run off interrupts with
> > minimal interrupt latency, the good news is that you don't have to modify
> > the kernel on ARM, and you certainly don't need any RT patches.
> > 
> > If you use the FIQ, then your FIQ latency will be the time it takes the
> > CPU to enter your FIQ function.  Since the kernel _never_ disables FIQs
> > in any way, FIQs have ultimate priority over everything else in the
> > system.
> > 
> 
> Aren't FIQ's only on some ARM's ? 

Yes, but please read the original mail.  I think you'll find my reply
is completely relevant to the question being posed, which was based
upon the AT91RM9200 SoC.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core