1 files changed, 19 insertions, 6 deletions

diff --git a/arch/arm/mach-versatile/pci.c b/arch/arm/mach-versatile/pci.c
index e92e5e0705bc..234740d90385 100644
--- a/arch/arm/mach-versatile/pci.c
+++ b/arch/arm/mach-versatile/pci.c
@@ -295,6 +295,19 @@ int __init pci_versatile_setup(int nr, struct pci_sys_data *sys)
         __raw_writel(PHYS_OFFSET, local_pci_cfg_base + PCI_BASE_ADDRESS_2);
 
         /*
+         * For many years the kernel and QEMU were symbiotically buggy
+         * in that they both assumed the same broken IRQ mapping.
+         * QEMU therefore attempts to auto-detect old broken kernels
+         * so that they still work on newer QEMU as they did on old
+         * QEMU. Since we now use the correct (ie matching-hardware)
+         * IRQ mapping we write a definitely different value to a
+         * PCI_INTERRUPT_LINE register to tell QEMU that we expect
+         * real hardware behaviour and it need not be backwards
+         * compatible for us. This write is harmless on real hardware.
+         */
+        __raw_writel(0, VERSATILE_PCI_VIRT_BASE+PCI_INTERRUPT_LINE);
+
+        /*
          * Do not to map Versatile FPGA PCI device into memory space
          */
         pci_slot_ignore |= (1 << myslot);
@@ -327,13 +340,13 @@ static int __init versatile_map_irq(const struct pci_dev *dev, u8 slot, u8 pin)
 {
         int irq;
 
-        /* slot,  pin,  irq
-         *  24     1     IRQ_SIC_PCI0
-         *  25     1     IRQ_SIC_PCI1
-         *  26     1     IRQ_SIC_PCI2
-         *  27     1     IRQ_SIC_PCI3
+        /*
+         * Slot INTA    INTB    INTC    INTD
+         * 31   PCI1    PCI2    PCI3    PCI0
+         * 30   PCI0    PCI1    PCI2    PCI3
+         * 29   PCI3    PCI0    PCI1    PCI2
          */
-        irq = IRQ_SIC_PCI0 + ((slot - 24 + pin - 1) & 3);
+        irq = IRQ_SIC_PCI0 + ((slot + 2 + pin - 1) & 3);
 
         return irq;
 }