PCI: Account fully optional bridge windows correctly

pbus_size_mem_optional() adds dev_res->add_size of a bridge window into
children_add_size when the window has a non-optional part. However, if the
bridge window is fully optional, only r_size is added (which is zero for
such a window).

Also, a second dev_res entry will be added by pci_dev_res_add_to_list()
into realloc_head for the bridge window (resulting in triggering the
realloc_head-must-be-fully-consumed sanity check after a single pass of the
resource assignment algorithm):

  WARNING: drivers/pci/setup-bus.c:2153 at pci_assign_unassigned_root_bus_resources+0xa5/0x260

Correct these problems by always adding dev_res->add_size for bridge
windows and not calling pci_dev_res_add_to_list() if the dev_res entry
exists.

Fixes: 6a5e64c ("PCI: Add pbus_mem_size_optional() to handle optional sizes")
Reported-by: RavitejaX Veesam <ravitejax.veesam@intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: RavitejaX Veesam <ravitejax.veesam@intel.com>
Link: https://patch.msgid.link/20260218223419.22366-1-ilpo.jarvinen@linux.intel.com

Author: ij-intel

drivers/pci/setup-bus.c

@@ -1224,31 +1224,34 @@ static bool pbus_size_mem_optional(struct pci_dev *dev, int resno,
 	struct resource *res = pci_resource_n(dev, resno);
 	bool optional = pci_resource_is_optional(dev, resno);
 	resource_size_t r_size = resource_size(res);
-	struct pci_dev_resource *dev_res;
+	struct pci_dev_resource *dev_res = NULL;
 
 	if (!realloc_head)
 		return false;
 
-	if (!optional) {
-		/*
-		 * Only bridges have optional sizes in realloc_head at this
-		 * point. As res_to_dev_res() walks the entire realloc_head
-		 * list, skip calling it when known unnecessary.
-		 */
-		if (!pci_resource_is_bridge_win(resno))
-			return false;
-
+	/*
+	 * Only bridges have optional sizes in realloc_head at this
+	 * point. As res_to_dev_res() walks the entire realloc_head
+	 * list, skip calling it when known unnecessary.
+	 */
+	if (pci_resource_is_bridge_win(resno)) {
 		dev_res = res_to_dev_res(realloc_head, res);
 		if (dev_res) {
 			*children_add_size += dev_res->add_size;
 			*add_align = max(*add_align, dev_res->min_align);
 		}
+	}
 
+	if (!optional)
 		return false;
-	}
 
-	/* Put SRIOV requested res to the optional list */
-	pci_dev_res_add_to_list(realloc_head, dev, res, 0, align);
+	/*
+	 * Put requested res to the optional list if not there yet (SR-IOV,
+	 * disabled ROM). Bridge windows with an optional part are already
+	 * on the list.
+	 */
+	if (!dev_res)
+		pci_dev_res_add_to_list(realloc_head, dev, res, 0, align);
 	*children_add_size += r_size;
 	*add_align = max(align, *add_align);