Re: [Xenomai-core] Handling PCI MSI interrupts

[Philippe Gerum <rpm@xenomai.org>]

Jeroen Van den Keybus wrote:
> Ok. I´ve found it. The MSI interrupt type uses its end() handler to 
> acknowledge the interrupt using ack_APIC_irq() (drivers/pci/msi.c). 
> Xenomai uses the ack() handler to expedite the acknowledgement of an 
> IRQ. In case of MSI, ack() is a NOP.
> 
> The main problem is that Xenomai redefines ack_APIC_irq() calls (they 
> become NOPs, as defined in apic.h). Maybe the ISRs used so far never 
> issued ack_APIC_irq() themselves, and used always the IO-APIC (which 
> contains the correct __ack_APIC_irq() call) ?
>

Really good spot, I overlooked this issue in the MSI support; thanks for digging it.

> I feel a bit awkward about changing msi.c .
> 
> Any opinions about how to change Xenomai / Linux ?
> 

It's definitely an Adeos issue and msi.c needs fixing. What about this patch, do 
things improve with it (against 2.6.15-ipipe-1.2-00)?

--- msi.c~	2006-01-03 04:21:10.000000000 +0100
+++ msi.c	2006-02-15 21:02:03.000000000 +0100
@@ -149,6 +149,15 @@
  	msi_set_mask_bit(vector, 0);
  }

+#ifdef CONFIG_IPIPE
+static void ack_MSI_irq(unsigned int vector)
+{
+    __ack_APIC_irq();
+}
+#else /* !CONFIG_IPIPE */
+#define ack_MSI_irq  mask_MSI_irq
+#endif /* CONFIG_IPIPE */
+
  static unsigned int startup_msi_irq_wo_maskbit(unsigned int vector)
  {
  	struct msi_desc *entry;
@@ -212,7 +221,7 @@
  	.shutdown	= shutdown_msi_irq,
  	.enable		= unmask_MSI_irq,
  	.disable	= mask_MSI_irq,
-	.ack		= mask_MSI_irq,
+	.ack		= ack_MSI_irq,
  	.end		= end_msi_irq_w_maskbit,
  	.set_affinity	= set_msi_irq_affinity
  };
@@ -228,7 +237,7 @@
  	.shutdown	= shutdown_msi_irq,
  	.enable		= unmask_MSI_irq,
  	.disable	= mask_MSI_irq,
-	.ack		= mask_MSI_irq,
+	.ack		= ack_MSI_irq,
  	.end		= end_msi_irq_w_maskbit,
  	.set_affinity	= set_msi_irq_affinity
  };

-- 

Philippe.