PCI: Factor pci_reassigndev_resource_alignment()

Pull the BAR size adjustment out into a new function,
pci_request_resource_alignment(), and add a comment about how and why we
increase the resource size and alignment.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index d22fb35be26e8eaa99f1245127cf1e00fcb57b5a..1d8bb090a40b93815cc558a181502557f27813ef 100644 (file)
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -5049,6 +5049,48 @@ out:
        return align;
 }
 
+static void pci_request_resource_alignment(struct pci_dev *dev, int bar,
+                                          resource_size_t align)
+{
+       struct resource *r = &dev->resource[bar];
+       resource_size_t size;
+
+       if (!(r->flags & IORESOURCE_MEM))
+               return;
+
+       if (r->flags & IORESOURCE_PCI_FIXED) {
+               dev_info(&dev->dev, "BAR%d %pR: ignoring requested alignment %#llx\n",
+                        bar, r, (unsigned long long)align);
+               return;
+       }
+
+       size = resource_size(r);
+       if (size < align) {
+
+               /*
+                * Increase the size of the resource.  BARs are aligned on
+                * their size, so when we reallocate space for this
+                * resource, we'll allocate it with the larger alignment.
+                * It also prevents assignment of any other BARs inside the
+                * size.  If we're requesting page alignment, this means no
+                * other BARs will share the page.
+                *
+                * This makes the resource larger than the hardware BAR,
+                * which may break drivers that compute things based on the
+                * resource size, e.g., to find registers at a fixed offset
+                * before the end of the BAR.  We hope users don't request
+                * alignment for such devices.
+                */
+               size = align;
+               dev_info(&dev->dev, "BAR%d %pR: requesting alignment to %#llx\n",
+                        bar, r, (unsigned long long)align);
+
+       }
+       r->flags |= IORESOURCE_UNSET;
+       r->end = size - 1;
+       r->start = 0;
+}
+
 /*
  * This function disables memory decoding and releases memory resources
  * of the device specified by kernel's boot parameter 'pci=resource_alignment='.
@@ -5060,7 +5102,7 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev)
 {
        int i;
        struct resource *r;
-       resource_size_t align, size;
+       resource_size_t align;
        u16 command;
 
        /*
@@ -5090,28 +5132,11 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev)
        command &= ~PCI_COMMAND_MEMORY;
        pci_write_config_word(dev, PCI_COMMAND, command);
 
-       for (i = 0; i <= PCI_ROM_RESOURCE; i++) {
-               r = &dev->resource[i];
-               if (!(r->flags & IORESOURCE_MEM))
-                       continue;
-               if (r->flags & IORESOURCE_PCI_FIXED) {
-                       dev_info(&dev->dev, "Ignoring requested alignment for BAR%d: %pR\n",
-                               i, r);
-                       continue;
-               }
+       for (i = 0; i <= PCI_ROM_RESOURCE; i++)
+               pci_request_resource_alignment(dev, i, align);
 
-               size = resource_size(r);
-               if (size < align) {
-                       size = align;
-                       dev_info(&dev->dev,
-                               "Rounding up size of resource #%d to %#llx.\n",
-                               i, (unsigned long long)size);
-               }
-               r->flags |= IORESOURCE_UNSET;
-               r->end = size - 1;
-               r->start = 0;
-       }
-       /* Need to disable bridge's resource window,
+       /*
+        * Need to disable bridge's resource window,
         * to enable the kernel to reassign new resource
         * window later on.
         */