Re: ARM Linux Suitability for Real-time Application

From: Andrew Lewis
Date: Wed Jun 22 2005 - 22:46:56 EST

Russell King wrote:
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

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.

Thanks for the suggestions. The FIQ solutions sounds like the one to use. I'll probably do a little testing sometime in the next few weeks to determine the maximum loading I can place on the processor when running some of the other peripherals simultaneously. If I have time I'll test the -RT patches as well and post up some numbers for this processor.

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