From: Tim Harvey <tharvey@gateworks.com>
Subject: [PATCH] PCI: imx6: add support for legacy irqs

The i.MX6 supports legacy IRQ's via 155,154,153,152.  When devices
are behind a PCIe-to-PCIe switch (at least for the TI XIO2001) the 
mapping is reversed from when they are behind a PCIe switch.

This patch still needs some review and clarification before going
upstream.
---
 drivers/pci/host/pcie-designware.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

--- a/drivers/pci/host/pcie-designware.c
+++ b/drivers/pci/host/pcie-designware.c
@@ -482,7 +482,26 @@ int dw_pcie_map_irq(const struct pci_dev
 {
 	struct pcie_port *pp = sys_to_pcie(dev->bus->sysdata);
 
-	return pp->irq;
+	/* TI XIO2001 PCIe-to-PCI bridge IRQs are flipped it seems */
+	if ( dev->bus && dev->bus->self
+	 && (dev->bus->self->vendor == 0x104c)
+	 && (dev->bus->self->device == 0x8240)) {
+		switch (pin) {
+		case 1: return pp->irq - 3;
+		case 2: return pp->irq - 2;
+		case 3: return pp->irq - 1;
+		case 4: return pp->irq;
+		default: return -1;
+		}
+	} else {
+		switch (pin) {
+		case 1: return pp->irq;
+		case 2: return pp->irq - 1;
+		case 3: return pp->irq - 2;
+		case 4: return pp->irq - 3;
+		default: return -1;
+		}
+	}
 }
 
 static struct hw_pci dw_pci = {