PCI: Add pbus_mem_size_optional() to handle optional sizes

The resource loop in pbus_size_mem() handles optional resources that are
either fully optional (SR-IOV and disabled Expansion ROMs) or bridge
windows that may be optional only for a part. The logic is a little
inconsistent when it comes to a bridge window that has only optional
children resources as it would be more natural to treat it similar to any
fully optional resource. As resource size should be zero in that case, it
shouldn't cause any bugs but it still seems useful to address the
inconsistency.

Place the optional size related code of pbus_size_mem() into
pbus_mem_size_optional() and add a check in pci_resource_is_optional()
for entirely optional bridge windows. Reorder the logic inside
pbus_mem_size_optional() such that fully optional resources are handled
the same irrespective of whether the resource is a bridge window or
not.

Additional motivation for this are the upcoming changes that add complexity
to the optional sizing logic due to Resizable BAR awareness.  The extra
logic would exceed any reasonable indentation level if the optional sizing
code is kept within the loop body.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20251219174036.16738-14-ilpo.jarvinen@linux.intel.com

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index 3d1d3cefcdbad0819d010fa2bc2bb997cd9e9125..3fcc7641c3740e300245c38badd3be876ec59ffc 100644 (file)
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -125,15 +125,6 @@ static resource_size_t get_res_add_size(struct list_head *head,
        return dev_res ? dev_res->add_size : 0;
 }
 
-static resource_size_t get_res_add_align(struct list_head *head,
-                                        struct resource *res)
-{
-       struct pci_dev_resource *dev_res;
-
-       dev_res = res_to_dev_res(head, res);
-       return dev_res ? dev_res->min_align : 0;
-}
-
 static void restore_dev_resource(struct pci_dev_resource *dev_res)
 {
        struct resource *res = dev_res->res;
@@ -386,6 +377,8 @@ bool pci_resource_is_optional(const struct pci_dev *dev, int resno)
                return true;
        if (resno == PCI_ROM_RESOURCE && !(res->flags & IORESOURCE_ROM_ENABLE))
                return true;
+       if (pci_resource_is_bridge_win(resno) && !resource_size(res))
+               return true;
 
        return false;
 }
@@ -1258,6 +1251,54 @@ static resource_size_t calculate_head_align(resource_size_t *aligns,
        return head_align;
 }
 
+/*
+ * pbus_size_mem_optional - Account optional resources in bridge window
+ *
+ * Account an optional resource or the optional part of the resource in bridge
+ * window size.
+ *
+ * Return: %true if the resource is entirely optional.
+ */
+static bool pbus_size_mem_optional(struct pci_dev *dev, int resno,
+                                  resource_size_t align,
+                                  struct list_head *realloc_head,
+                                  resource_size_t *add_align,
+                                  resource_size_t *children_add_size)
+{
+       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;
+
+       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;
+
+               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);
+               }
+
+               return false;
+       }
+
+       /* Put SRIOV requested res to the optional list */
+       add_to_list(realloc_head, dev, res, 0, align);
+       *children_add_size += r_size;
+       *add_align = max(align, *add_align);
+
+       return true;
+}
+
 /**
  * pbus_size_mem() - Size the memory window of a given bus
  *
@@ -1284,7 +1325,6 @@ static void pbus_size_mem(struct pci_bus *bus, struct resource *b_res,
        resource_size_t aligns[28] = {}; /* Alignments from 1MB to 128TB */
        int order, max_order;
        resource_size_t children_add_size = 0;
-       resource_size_t children_add_align = 0;
        resource_size_t add_align = 0;
 
        if (!b_res)
@@ -1311,7 +1351,6 @@ static void pbus_size_mem(struct pci_bus *bus, struct resource *b_res,
                        if (b_res != pbus_select_window(bus, r))
                                continue;
 
-                       r_size = resource_size(r);
                        align = pci_resource_alignment(dev, r);
                        /*
                         * aligns[0] is for 1MB (since bridge memory
@@ -1327,25 +1366,17 @@ static void pbus_size_mem(struct pci_bus *bus, struct resource *b_res,
                                continue;
                        }
 
-                       /* Put SRIOV requested res to the optional list */
-                       if (realloc_head && pci_resource_is_optional(dev, i)) {
-                               add_align = max(align, add_align);
-                               add_to_list(realloc_head, dev, r, 0, 0 /* Don't care */);
-                               children_add_size += r_size;
+                       if (pbus_size_mem_optional(dev, i, align,
+                                                  realloc_head, &add_align,
+                                                  &children_add_size))
                                continue;
-                       }
 
+                       r_size = resource_size(r);
                        size += max(r_size, align);
 
                        aligns[order] += align;
                        if (order > max_order)
                                max_order = order;
-
-                       if (realloc_head) {
-                               children_add_size += get_res_add_size(realloc_head, r);
-                               children_add_align = get_res_add_align(realloc_head, r);
-                               add_align = max(add_align, children_add_align);
-                       }
                }
        }