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-rw-r--r--hw/ppc/ppc440_pcix.c11
1 files changed, 9 insertions, 2 deletions
diff --git a/hw/ppc/ppc440_pcix.c b/hw/ppc/ppc440_pcix.c
index ee952314c8..eb1290ffc8 100644
--- a/hw/ppc/ppc440_pcix.c
+++ b/hw/ppc/ppc440_pcix.c
@@ -415,8 +415,15 @@ static void ppc440_pcix_reset(DeviceState *dev)
s->sts = 0;
}
-/* All pins from each slot are tied to a single board IRQ.
- * This may need further refactoring for other boards. */
+/*
+ * All four IRQ[ABCD] pins from all slots are tied to a single board
+ * IRQ, so our mapping function here maps everything to IRQ 0.
+ * The code in pci_change_irq_level() tracks the number of times
+ * the mapped IRQ is asserted and deasserted, so if multiple devices
+ * assert an IRQ at the same time the behaviour is correct.
+ *
+ * This may need further refactoring for boards that use multiple IRQ lines.
+ */
static int ppc440_pcix_map_irq(PCIDevice *pci_dev, int irq_num)
{
trace_ppc440_pcix_map_irq(pci_dev->devfn, irq_num, 0);