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author | Bjorn Helgaas <bhelgaas@google.com> | 2014-05-19 18:32:18 -0600 |
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committer | Bjorn Helgaas <bhelgaas@google.com> | 2014-05-23 12:40:49 -0600 |
commit | 67d29b5c6c40e91b124695e9250c2fd24915e24a (patch) | |
tree | 38def8abdc769db7adc071f445afb00435849af9 /drivers/pci/setup-res.c | |
parent | d3689df04445c568c8b3dfcd8db4b562e1b18cfb (diff) | |
download | linux-stable-67d29b5c6c40e91b124695e9250c2fd24915e24a.tar.gz linux-stable-67d29b5c6c40e91b124695e9250c2fd24915e24a.tar.bz2 linux-stable-67d29b5c6c40e91b124695e9250c2fd24915e24a.zip |
PCI: Add resource allocation comments
Add comments in the code to match the allocation strategy of 7c671426dfc3
("PCI: Restrict 64-bit prefetchable bridge windows to 64-bit resources").
No functional change.
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Diffstat (limited to 'drivers/pci/setup-res.c')
-rw-r--r-- | drivers/pci/setup-res.c | 35 |
1 files changed, 19 insertions, 16 deletions
diff --git a/drivers/pci/setup-res.c b/drivers/pci/setup-res.c index 3bdac9dc4a88..3da2542eb4df 100644 --- a/drivers/pci/setup-res.c +++ b/drivers/pci/setup-res.c @@ -209,20 +209,25 @@ static int __pci_assign_resource(struct pci_bus *bus, struct pci_dev *dev, min = (res->flags & IORESOURCE_IO) ? PCIBIOS_MIN_IO : PCIBIOS_MIN_MEM; - /* First, try exact prefetching match.. */ + /* + * First, try exact prefetching match. Even if a 64-bit + * prefetchable bridge window is below 4GB, we can't put a 32-bit + * prefetchable resource in it because pbus_size_mem() assumes a + * 64-bit window will contain no 32-bit resources. If we assign + * things differently than they were sized, not everything will fit. + */ ret = pci_bus_alloc_resource(bus, res, size, align, min, IORESOURCE_PREFETCH | IORESOURCE_MEM_64, pcibios_align_resource, dev); if (ret == 0) return 0; + /* + * If the prefetchable window is only 32 bits wide, we can put + * 64-bit prefetchable resources in it. + */ if ((res->flags & (IORESOURCE_PREFETCH | IORESOURCE_MEM_64)) == (IORESOURCE_PREFETCH | IORESOURCE_MEM_64)) { - /* - * That failed. - * - * Try 32bit pref - */ ret = pci_bus_alloc_resource(bus, res, size, align, min, IORESOURCE_PREFETCH, pcibios_align_resource, dev); @@ -230,18 +235,16 @@ static int __pci_assign_resource(struct pci_bus *bus, struct pci_dev *dev, return 0; } - if (res->flags & (IORESOURCE_PREFETCH | IORESOURCE_MEM_64)) { - /* - * That failed. - * - * But a prefetching area can handle a non-prefetching - * window (it will just not perform as well). - * - * Also can put 64bit under 32bit range. (below 4g). - */ + /* + * If we didn't find a better match, we can put any memory resource + * in a non-prefetchable window. If this resource is 32 bits and + * non-prefetchable, the first call already tried the only possibility + * so we don't need to try again. + */ + if (res->flags & (IORESOURCE_PREFETCH | IORESOURCE_MEM_64)) ret = pci_bus_alloc_resource(bus, res, size, align, min, 0, pcibios_align_resource, dev); - } + return ret; } |