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.
--
Regards
Anders Blomdell
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