[ECOS] Possible fix for interrupt latency problems on Arm

Jürgen Lambrecht J.Lambrecht@televic.com
Mon Jul 31 08:32:00 GMT 2006


Hello Mike,

I'm just back from holidays - you didn't receive any reply on your mail?

I also use an ARM (ARM7TDMI, eb55 board based), so I'm interested in the
problem. I don't have interrupt latency problems (yet), but I will ask my
colleague.

This is list is normally a good place to start committing modifications..
For the patch, you must send a diff (you can find examples in the mailing
list), and :
"Next time, please send to ecos-patches@ecos.sourceware.org.  Also
include a ChangeLog entry so we don't have to fabricate one."

Kind regards,
Juergen

---
Jürgen Lambrecht
Development Engineer
Televic Transport Systems
http://www.televic.com
Televic NV / SA (main office)  	
Leo Bekaertlaan 1
B-8870 Izegem
Tel: +32 (0)51 303045
Fax: +32 (0)51 310670


Mike wrote:

> I have been looking at why my Arm LPC2220 board occasionally gets 
> terrible interrupt latencies. This happens particularly when the 
> interrupt I'm interested in occurs whilst ecos is doing processing after 
> a TIMER0 (ecos RTC) interrupt.
> 
> It seems that interrupt_end() is called from 
> hal/arm/arch/current/src/vectors.s with interrupts disabled, whereas it 
> looks to me like interrupt_end() has been designed to run with 
> interrupts enabled in order for DSRs to be interruptible.
> 
> I have modified my own vectors.s by inserting the following immediately 
> before the call to interrupt_end():
> // Enable interrupts
> mrs r4,cpsr
> bic r4,r4,#CPSR_IRQ_DISABLE|CPSR_FIQ_DISABLE
> msr cpsr,r4
> 
> This seems to work for me, but I would appreciate feedback if this is a 
> sane and wise thing to do.
> 
> As a newbie, how do I submit such modifications for inclusion in the 
> repository?
> 
> Thanks,
> Mike
> 
> 



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