PCI: cadence: Use AXI region 0 to signal interrupts from EP

The IRQ physical address is allocated from region 0, rather than
the highest region. Update the driver to reserve this region in
the bitmap and to use region 0 for all types of interrupt.

This corrects a problem which prevents the interrupt being
signalled correctly if using the first address in the AXI region,
since an offset of zero will always be mapped to region 0.

Fixes: 37dddf14 ("PCI: cadence: Add EndPoint Controller driver for Cadence PCIe controller")
Signed-off-by: Alan Douglas <adouglas@cadence.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

drivers/pci/controller/pcie-cadence-ep.c

@@ -258,7 +258,6 @@ static void cdns_pcie_ep_assert_intx(struct cdns_pcie_ep *ep, u8 fn,
 				     u8 intx, bool is_asserted)
 {
 	struct cdns_pcie *pcie = &ep->pcie;
-	u32 r = ep->max_regions - 1;
 	u32 offset;
 	u16 status;
 	u8 msg_code;
@@ -268,8 +267,8 @@ static void cdns_pcie_ep_assert_intx(struct cdns_pcie_ep *ep, u8 fn,
 	/* Set the outbound region if needed. */
 	if (unlikely(ep->irq_pci_addr != CDNS_PCIE_EP_IRQ_PCI_ADDR_LEGACY ||
 		     ep->irq_pci_fn != fn)) {
-		/* Last region was reserved for IRQ writes. */
-		cdns_pcie_set_outbound_region_for_normal_msg(pcie, fn, r,
+		/* First region was reserved for IRQ writes. */
+		cdns_pcie_set_outbound_region_for_normal_msg(pcie, fn, 0,
 							     ep->irq_phys_addr);
 		ep->irq_pci_addr = CDNS_PCIE_EP_IRQ_PCI_ADDR_LEGACY;
 		ep->irq_pci_fn = fn;
@@ -347,8 +346,8 @@ static int cdns_pcie_ep_send_msi_irq(struct cdns_pcie_ep *ep, u8 fn,
 	/* Set the outbound region if needed. */
 	if (unlikely(ep->irq_pci_addr != (pci_addr & ~pci_addr_mask) ||
 		     ep->irq_pci_fn != fn)) {
-		/* Last region was reserved for IRQ writes. */
-		cdns_pcie_set_outbound_region(pcie, fn, ep->max_regions - 1,
+		/* First region was reserved for IRQ writes. */
+		cdns_pcie_set_outbound_region(pcie, fn, 0,
 					      false,
 					      ep->irq_phys_addr,
 					      pci_addr & ~pci_addr_mask,
@@ -517,6 +516,8 @@ static int cdns_pcie_ep_probe(struct platform_device *pdev)
 		goto free_epc_mem;
 	}
 	ep->irq_pci_addr = CDNS_PCIE_EP_IRQ_PCI_ADDR_NONE;
+	/* Reserve region 0 for IRQs */
+	set_bit(0, &ep->ob_region_map);
 
 	return 0;