PCI: thunder-pem: Fix legacy firmware PEM-specific resources

SZ_16M PEM resource size includes PEM-specific register and its children
resources. Reservation of the whole SZ_16M range leads to child device
driver failure when pcieport driver is requesting resources:

  pcieport 0004:1f:00.0: can't enable device: BAR 0 [mem 0x87e0c0f00000-0x87e0c0ffffff 64bit] not claimed

So we cannot reserve full 16M here and instead we want to reserve
PEM-specific register only which is SZ_64K.

At the end increase PEM resource to SZ_16M since this is what
thunder_pem_init() call expects for proper initialization.

Fixes: 9abb27c7 ("PCI: thunder-pem: Add legacy firmware support for Cavium ThunderX host controller")
Signed-off-by: Tomasz Nowicki <tn@semihalf.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: stable@vger.kernel.org	# v4.10+

drivers/pci/host/pci-thunder-pem.c

@@ -375,7 +375,6 @@ static void thunder_pem_legacy_fw(struct acpi_pci_root *root,
 	index -= node * PEM_MAX_DOM_IN_NODE;
 	res_pem->start = PEM_RES_BASE | FIELD_PREP(PEM_NODE_MASK, node) |
 					FIELD_PREP(PEM_INDX_MASK, index);
-	res_pem->end = res_pem->start + SZ_16M - 1;
 	res_pem->flags = IORESOURCE_MEM;
 }
 
@@ -399,8 +398,15 @@ static int thunder_pem_acpi_init(struct pci_config_window *cfg)
 	 */
 	if (ret) {
 		thunder_pem_legacy_fw(root, res_pem);
-		/* Reserve PEM-specific resources and PCI configuration space */
+		/*
+		 * Reserve 64K size PEM specific resources. The full 16M range
+		 * size is required for thunder_pem_init() call.
+		 */
+		res_pem->end = res_pem->start + SZ_64K - 1;
 		thunder_pem_reserve_range(dev, root->segment, res_pem);
+		res_pem->end = res_pem->start + SZ_16M - 1;
+
+		/* Reserve PCI configuration space as well. */
 		thunder_pem_reserve_range(dev, root->segment, &cfg->res);
 	}