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)
@@ -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)

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).



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