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Date: Tue, 07 Feb 2006 17:16:11 +0100
From: Philippe Gerum <rpm@xenomai.org>
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Subject: Re: [Xenomai-core] [PATCH] Slow is faster arch/ppc/syslib/open_pic.c
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To: Anders Blomdell <anders.blomdell@domain.hid>
Cc: xenomai@xenomai.org

Anders Blomdell wrote:
> When trying to run Xenomai on PowerPC with OpenPIC, I have (finally) 
> found that interrupt latency is much improved with the following patch:
> 
> 
> 
> --- arch/ppc/syslib/open_pic.c~ 2006-01-08 03:15:24.000000000 +0100
> +++ arch/ppc/syslib/open_pic.c  2006-02-07 16:56:14.000000000 +0100
> @@ -820,7 +820,7 @@
>   */
>  static void openpic_ack_irq(unsigned int irq_nr)
>  {
> -#ifdef __SLOW_VERSION__
> +#if defined(__SLOW_VERSION__) || defined(CONFIG_IPIPE)
>         openpic_disable_irq(irq_nr);
>         openpic_eoi();
>  #else
> @@ -831,7 +831,7 @@
> 
>  static void openpic_end_irq(unsigned int irq_nr)
>  {
> -#ifdef __SLOW_VERSION__
> +#if defined(__SLOW_VERSION__) || defined(CONFIG_IPIPE)
>         if (!(irq_desc[irq_nr].status & (IRQ_DISABLED|IRQ_INPROGRESS))
>             && irq_desc[irq_nr].action)
>                 openpic_enable_irq(irq_nr);
> 
> 
> 
> The reason for this, is that the fast version doesn't call openpic_eoi 
> until the interrupt is ended, which means that all RT-interrupts are 
> delayed by a pending Linux interrupt.
> 

Gasp. Will check on my Icecube asap, thanks (a lot).

-- 

Philippe.