PCI: Add weak pcibios_window_alignment() interface
This patch implements a weak function to return the default I/O or memory
window alignment for a P2P bridge. By default, I/O windows are aligned to
4KiB or 1KiB and memory windows are aligned to 4MiB. Some platforms, e.g.,
powernv, have special alignment requirements and can override
pcibios_window_alignment().
[bhelgaas: changelog]
Signed-off-by: Gavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index fb50613..896f06e 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -697,6 +697,38 @@
return size;
}
+resource_size_t __weak pcibios_window_alignment(struct pci_bus *bus,
+ unsigned long type)
+{
+ return 1;
+}
+
+#define PCI_P2P_DEFAULT_MEM_ALIGN 0x100000 /* 1MiB */
+#define PCI_P2P_DEFAULT_IO_ALIGN 0x1000 /* 4KiB */
+#define PCI_P2P_DEFAULT_IO_ALIGN_1K 0x400 /* 1KiB */
+
+static resource_size_t window_alignment(struct pci_bus *bus,
+ unsigned long type)
+{
+ resource_size_t align = 1, arch_align;
+
+ if (type & IORESOURCE_MEM)
+ align = PCI_P2P_DEFAULT_MEM_ALIGN;
+ else if (type & IORESOURCE_IO) {
+ /*
+ * Per spec, I/O windows are 4K-aligned, but some
+ * bridges have an extension to support 1K alignment.
+ */
+ if (bus->self->io_window_1k)
+ align = PCI_P2P_DEFAULT_IO_ALIGN_1K;
+ else
+ align = PCI_P2P_DEFAULT_IO_ALIGN;
+ }
+
+ arch_align = pcibios_window_alignment(bus, type);
+ return max(align, arch_align);
+}
+
/**
* pbus_size_io() - size the io window of a given bus
*